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C Programming

2007-05-13T06:12:00.000-07:00

C is a general-purpose, procedural, imperative computer programming language developed in 1972 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system.^[1] It has since spread to many other platforms. Although predominantly used for system software,^[2]^[3] C is also widely used for applications. C has also greatly influenced many other popular languages,^[4] especially C++, which was designed as an enhancement to C.

[edit] Philosophy

C is an imperative (procedural) systems implementation language. Among its minimalistic design goals were that it could be compiled in a straightforward manner using a relatively simple compiler, provide low-level access to memory, generate only a few machine language instructions for each of its core language elements, and not require extensive run-time support. C is therefore suitable for many applications that had traditionally been implemented in assembly language.

Despite its low-level capabilities, the language was designed to encourage machine-independent programming. A standards-compliant and portably written C program can be compiled for a very wide variety of computer platforms and operating systems with minimal change to its source code. The language has become available on a very wide range of platforms, from embedded microcontrollers to supercomputers.

[edit] Characteristics

As most imperative languages in the ALGOL tradition, C has facilities for structured programming and allows lexical variable scope and recursion, while a static type system prevents many unintended operations. Parameters of C functions are always passed by value. Pass-by-reference is achieved in C by explicitly passing pointer values. Heterogeneous aggregate data types (the struct in C) allow related data elements to be combined and manipulated as a unit. C has around 30 reserved keywords and the source text is free-format, using semicolon as a statement terminator (not a delimiter).

C also exhibits the following more specific characteristics:

Non-nestable function definitions, although variables may be hidden in blocks to any level of depth
Partially weak typing, for instance, characters can be used as integers in a way similar to assembly
Low-level access to computer memory via machine addresses and typed pointers
Function pointers allowing for a rudimentary form of closures and runtime polymorphism
Array indexing as a secondary notion, defined in terms of pointer arithmetic
A standardized C preprocessor for macro definition, source code file inclusion, conditional compilation, etc.
Complex functionality such as I/O and mathematical functions consistently delegated to library routines
Syntax divergent from ALGOL, often following the lead of C's predecessor B, for example using
- { ... } rather than ALGOL's begin ... end
- the equal-sign for assignment (copying), much like Fortran
- two consecutive equal-signs to test for equality (compare to .EQ. in Fortran or the equal-sign in BASIC)
- && and || in place of ALGOL's and and or, which
  - are syntactically distinct from the bit-wise operators & and | (B used & and | in both meanings)
  - never evaluate the right operand if the result can be determined from the left alone (short-circuit evaluation)
- a large number of compound operators, such as +=, ++, etc.

[edit] History

[edit] Early developments

The initial development of C occurred at AT&T Bell Labs between 1969 and 1973; according to Ritchie, the most creative period occurred in 1972. It was named "C" because many of its features were derived from an earlier language called "B," which according to Ken Thompson was a stripped down version of the BCPL programming language.

There are many legends as to the origin of C and the closely related Unix operating system, including these:

The development of Unix was the result of programmers' desire to play the Space Travel computer game.[1] They had been playing it on their company's mainframe, but as it was underpowered and had to support about 100 users, Thompson and Ritchie found they did not have sufficient control over the spaceship to avoid collisions with the wandering space rocks. This led to the decision to port the game to an idle PDP-7 in the office. As this machine lacked an operating system, the two set out to develop one, based on several ideas from colleagues. Eventually it was decided to port the operating system to the office's PDP-11, but faced with the daunting task of translating a large body of custom-written assembly language code, the programmers began considering using a portable, high-level language so that the OS could be ported easily from one computer to another. They looked at using B, but it lacked functionality to take advantage of some of the PDP-11's advanced features. This led to the development of an early version of the C programming language.
The justification for obtaining the original computer to be used in developing the Unix operating system was to create a system to automate the filing of patents. The original version of the Unix system was developed in assembly language. Later, nearly all of the operating system was rewritten in C, an unprecedented move at a time when nearly all operating systems were written in assembly.

By 1973, the C language had become powerful enough that most of the Unix kernel, originally written in PDP-11 assembly language, was rewritten in C. This was one of the first operating system kernels implemented in a language other than assembly. (Earlier instances include the Multics system (written in PL/I), and MCP (Master Control Program) for the Burroughs B5000 written in ALGOL in 1961.)

[edit] K&R C

In 1978, Dennis Ritchie and Brian Kernighan published the first edition of The C Programming Language. This book, known to C programmers as "K&R", served for many years as an informal specification of the language. The version of C that it describes is commonly referred to as "K&R C". The second edition of the book covers the later ANSI C standard.

K&R introduced several language features:

struct data types
long int data type
unsigned int data type
The =- operator was changed to -= to remove the semantic ambiguity created by the construct i=-10, which could be interpreted as either i =- 10 or i = -10

For many years after the introduction of ANSI C, K&R C was still considered the "lowest common denominator" to which C programmers restricted themselves when maximum portability was desired, since many older compilers were still in use, and because carefully written K&R C code can be legal ANSI C as well.

In early versions of C, only functions that returned a non-integer value needed to be declared if used before the function definition; a function used without any previous declaration was assumed to return an integer.

For example:

long int SomeFunction();
int OtherFunction();

int CallingFunction()
{
   long int test1;
   int test2;

   test1 = SomeFunction();
   if (test1 > 0)
         test2 = 0;
   else
         test2 = OtherFunction();

   return test2;
}

In the example, both SomeFunction and OtherFunction were declared before use. In K&R, OtherFunction declaration could be omitted.

Since K&R function declarations did not include any information about function arguments, function parameter type checks were not performed, although some compilers would issue a warning message if a local function was called with the wrong number of arguments, or if multiple calls to an external function used different numbers of arguments. Separate tools such as Unix's lint utility were developed that (among other things) could check for consistency of function use across multiple source files.

In the years following the publication of K&R C, several unofficial features were added to the language (since there was no standard), supported by compilers from AT&T and some other vendors. These included:

void functions
Functions returning struct or union types (rather than pointers)
Assignment for struct data types
const qualifier to make an object read-only
Enumerated types

The large number of extensions and lack of a standard library, together with the language popularity and the fact that not even the Unix compilers precisely implemented the K&R specification, led to the necessity of standardization.

[edit] ANSI C and ISO C

It has been suggested that this article or section be merged with ANSI C. (Discuss)

The C Programming Language, 2nd edition, is a widely used reference on ANSI C.

During the late 1970s, C began to replace BASIC as the leading microcomputer programming language. During the 1980s, it was adopted for use with the IBM PC, and its popularity began to increase significantly. At the same time, Bjarne Stroustrup and others at Bell Labs began work on adding object-oriented programming language constructs to C, resulting in the language now called C++.

In 1983, the American National Standards Institute (ANSI) formed a committee, X3J11, to establish a standard specification of C. In 1989, the standard was ratified as ANSI X3.159-1989 "Programming Language C." This version of the language is often referred to as ANSI C, Standard C, or sometimes C89.

In 1990, the ANSI C standard (with a few minor modifications) was adopted by the International Organization for Standardization (ISO) as ISO/IEC 9899:1990. This version is sometimes called C90. Therefore, the terms "C89" and "C90" refer to essentially the same language.

One of the aims of the C standardization process was to produce a superset of K&R C, incorporating many of the unofficial features subsequently introduced. However, the standards committee also included several new features, such as function prototypes (borrowed from C++), void pointers, support for international character sets and locales, and a more capable preprocessor. The syntax for parameter declarations was also augmented to include the C++ style:

int main(int argc, char **argv)
{
...
}

although the K&R interface

int main(argc, argv)
   int argc;
   char **argv;
{
...
}

continued to be permitted, for compatibility with existing source code.

C89 is supported by current C compilers, and most C code being written nowadays is based on it. Any program written only in Standard C and without any hardware-dependent assumptions will run correctly on any platform with a conforming C implementation, within its resource limits. Without such precautions, programs may compile only on a certain platform or with a particular compiler, due, for example, to the use of non-standard libraries, such as GUI libraries, or to a reliance on compiler- or platform-specific attributes such as the exact size of data types and byte endianness.

In cases where code must be compilable by either standard-conforming or K&R C-based compilers, the __STDC__ macro can be used to split the code into Standard and K&R sections, in order to take advantage of features available only in Standard C.

#ifdef __STDC__
extern int getopt(int,char * const *,const char *);
#else
extern int getopt();
#endif

In the above example, a compiler which has defined the __STDC__ macro (as mandated by the C standard) only interprets the line following the ifdef command. In other, nonstandard compilers which don't define the macro, only the line following the else command is interpreted.

[edit] C99

Note: C99 is also the name of a C compiler for the Texas Instruments TI-99/4A home computer. Aside from being a C compiler, it is otherwise unrelated.

After the ANSI standardization process, the C language specification remained relatively static for some time, whereas C++ continued to evolve, largely during its own standardization effort. Normative Amendment 1 created a new standard for the C language in 1995, but only to correct some details of the C89 standard and to add more extensive support for international character sets. However, the standard underwent further revision in the late 1990s, leading to the publication of ISO 9899:1999 in 1999. This standard is commonly referred to as "C99." It was adopted as an ANSI standard in March 2000.

C99 introduced several new features, many of which had already been implemented as extensions in several compilers:

Inline functions
Variables can be declared anywhere (as in C++), rather than only after another declaration or the start of a compound statement
Several new data types, including long long int, optional extended integer types, an explicit boolean data type, and a complex type to represent complex numbers
Variable-length arrays
Support for one-line comments beginning with //, as in BCPL or C++
New library functions, such as snprintf
New header files, such as stdbool.h and inttypes.h
Type-generic math functions (tgmath.h)
Improved support for IEEE floating point
Designated initializers
Compound literals
Support for variadic macros (macros of variable arity)
restrict qualification to allow more aggressive code optimization

C99 is for the most part upward-compatible with C90, but is stricter in some ways; in particular, a declaration that lacks a type specifier no longer has int implicitly assumed. The C standards committee decided that it was of more value for compilers to diagnose inadvertent omission of the type specifier than to silently process legacy code that relied on implicit int. In practice, compilers are likely to diagnose the omission but also assume int and continue translating the program.

GCC and other C compilers now support many of the new features of C99. However, there has been less support from vendors such as Microsoft and Borland that have mainly focused on C++, since C++ provides similar functionality improvement.

GCC, despite its extensive C99 support, is still not a completely compliant implementation; several key features are missing or don't work correctly.[2]

A standard macro __STDC_VERSION__ is defined with value 199901L to indicate that C99 support is available. As with the __STDC__ macro for C90, __STDC_VERSION__ can be used to write code that will compile differently for C90 and C99 compilers, as in this example that ensures that inline is available in either case.

#if __STDC_VERSION__ >= 199901L
 /* "inline" is a keyword */
#else
# define inline /* nothing */
#endif

[edit] Usage

C's primary use is for "system programming", including implementing operating systems and embedded system applications, due to a combination of desirable characteristics such as code portability and efficiency, ability to access specific hardware addresses, ability to "pun" types to match externally imposed data access requirements, and low runtime demand on system resources.

C has also been widely used to implement end-user applications, although as applications became larger much of that development shifted to other, higher-level languages.

One consequence of C's wide acceptance and efficiency is that the compilers, libraries, and interpreters of other higher-level languages are often implemented in C.

C is used as an intermediate language by some higher-level languages. This is implemented in one of two ways, as languages which:

Emit C source code, and one or more other representations: machine code, object code, and/or bytecodes. Examples: some Lisp dialects (Lush), Squeak's C-subset Slang.
Emit C source code only, and no other representation. Examples: Eiffel, Sather; Esterel.

C source code is then input to a C compiler, which then outputs finished machine or object code. This is done to gain portability (C compilers exist for nearly all platforms) and to avoid having to develop machine-specific code generators.

Unfortunately, C was designed as a programming language, not as a compiler target language, and is thus less than ideal for use as an intermediate language. This has led to development of C-based intermediate languages such as C--.

[edit] Syntax

Main article: C syntax

Unlike languages such as FORTRAN 77, C source code is free-form which allows arbitrary use of whitespace to format code, rather than column-based or text-line-based restrictions. Comments may appear either between the delimiters /* and */, or (in C99) following // until the end of the line.

Each source file contains declarations and function definitions. Function definitions, in turn, contain declarations and statements. Declarations either define new types using keywords such as struct, union, and enum, or assign types to and perhaps reserve storage for new variables, usually by writing the type followed by the variable name. Keywords such as char and int, as well as the pointer-to symbol *, specify built-in types. Sections of code are enclosed in braces ({ and }) to indicate the extent to which declarations and control structures apply.

As an imperative language, C depends on statements to do most of the work. Most statements are expression statements which simply evaluate an expression; as a side effect, variables may receive new values. Control-flow statements are also available for conditional or iterative execution, constructed with reserved keywords such as if, else, switch, do, while, and for. Arbitrary jumps are possible with goto. A variety of built-in operators perform primitive arithmetic, Boolean logical, comparative, bitwise logical, and array indexing operations and assignment. Expressions can also invoke functions, including a large number of standard library functions, for performing many common tasks.

[edit] Operator precedence

Main article: Operators in C and C++

What follows is the list of C operators sorted from highest to lowest priority. Operators of same priority are presented on the same line. "R→L" associativity means that adjacent operators of the same priority are executed from right to left, and conversely for "L→R".

Class	Associativity	Operators
Select	L→R	(...) [...] -> .
Unary	R→L	! ~ + - * & (type) sizeof ++ --
Binary arithmetical	L→R	* / %
Binary arithmetical	L→R	+ -
Shift	L→R	<< >>
Comparison	L→R	< <= > >=
Comparison	L→R	== !=
Binary bitwise	L→R	&
Binary bitwise	L→R	^
Binary bitwise	L→R	\|
Binary boolean	L→R	&&
Binary boolean	L→R	\|\|
Ternary	R→L	?...:
Assignments	R→L	= += -= *= /= &= \|= ^= <<= >>=
Sequence	L→R	,

[edit] "hello, world" example

The following simple application appeared in the first edition of K&R, and has become the model for an introductory program in most programming textbooks, regardless of programming language. The program prints out "hello, world" to the standard output, which is usually a terminal or screen display. Standard output might also be a file or some other hardware device, depending on how standard output is mapped at the time the program is executed.

main()
{
   printf("hello, world\n");
}

The above program will compile on most modern compilers that are not in compliance mode, but does not meet the requirements of either C89 or C99. Compiling this program in C99 compliance mode will result in warning or error messages.^[5] A compliant version of the above program follows:

#include 

int main(void)
{
   printf("hello, world\n");

   return 0;
}

What follows is a line-by-line analysis of the above program:

#include

This first line of the program is a preprocessing directive, #include. This causes the preprocessor — the first tool to examine source code when it is compiled — to substitute the line with the entire text of the stdio.h file. The header file stdio.h contains declarations for standard input and output functions such as printf. The angle brackets surrounding stdio.h indicate that stdio.h can be found using an implementation-defined search strategy. Double quotes may also be used for headers, thus allowing the implementation to supply (up to) two strategies. Typically, angle brackets are reserved for headers supplied by the C compiler, and double quotes for local or installation-specific headers.

int main(void)

This next line indicates that a function named main is being defined. The main function serves a special purpose in C programs: When the program is executed, main is the function called by the run-time environment—otherwise it acts like any other function in the program. The type specifier int indicates that the return value, the value of evaluating the main function that is returned to its invoker (in this case the run-time environment), is an integer. The keyword (void) in between the parentheses indicates that the main function takes no arguments. See also void.^[6]

This opening curly brace indicates the beginning of the definition of the main function.

    printf("hello, world\n");

This line calls (executes the code for) a function named printf, which is declared in the included header stdio.h and supplied from a system library. In this call, the printf function is passed (provided with) a single argument, the address of the first character in the string literal "hello, world\n". The string literal is an unnamed array with elements of type char, set up automatically by the compiler with a final 0-valued character to mark the end of the array (printf needs to know this). The \n is an escape sequence that C translates to the newline character, which on output signifies the beginning of the next line. The return value of the printf function is of type int, but it is silently discarded since it is not used by the caller. A more careful program might test the return value to determine whether or not the printf function succeeded.

    return 0;

This line terminates the execution of the main function and causes it to return the integer value 0, which is interpreted by the run-time system as an exit code indicating successful execution.

This closing curly brace indicates the end of the code for the main function.

If the above code were compiled and executed, it would do the following:

Print the string "hello, world" onto the standard output device (typically but not always a terminal),
Move the current position indicator to the beginning of the next line, and
Return a "successful" exit status to the calling process (such as a command shell or script).

[edit] Data structures

C has a static weak typing type system that shares some similarities with that of other ALGOL descendants such as Pascal. There are built-in types for integers of various sizes, both signed and unsigned, floating-point numbers, characters, and enumerated types (enum). C99 added a Boolean datatype. There are also derived types including arrays, pointers, records (struct), and untagged unions (union).

C is often used in low-level systems programming where "escapes" from the type system may be necessary. The compiler attempts to ensure type correctness of most expressions, but the programmer can override the checks in various ways, either by using a type cast to explicitly convert a value from one type to another, or by using pointers or unions to reinterpret the underlying bits of a value in some other way. (The use of type casts obviously sacrifices some of the safety normally provided by the type system.)

[edit] Pointers

C also allows the use of pointers, a very simple type of reference that records, in effect, the address or location of an object or function in memory. Pointers can be dereferenced to access the data stored at the address pointed to, or to invoke the pointed-to function. Pointers can be manipulated using normal assignments and also pointer arithmetic. The run-time representation of a pointer value is typically a raw memory address, but since a pointer's type includes the type of the thing pointed to, expressions including pointers can be type-checked at compile time. Pointer arithmetic is automatically scaled by the size of the pointed-to data type. (See #Array↔pointer interchangeability below.) Pointers are used for many different purposes in C. Text strings are commonly manipulated using pointers into arrays of characters. Dynamic memory allocation, which is described below, is performed using pointers. Pointers to functions are useful for callbacks from event handlers.

A null pointer is a pointer value that points to no valid location (it is often represented by address zero). Dereferencing a null pointer is therefore meaningless, typically resulting in a run-time error. Null pointers are useful for indicating special cases such as no next pointer in the final node of a linked list, or as an error indication from functions returning pointers. Void pointers (void *) also exist and point to objects of unknown type, and can therefore be used as "generic" data pointers. Since the size and type of the pointed-to object is not known, void pointers cannot be dereferenced, nor is pointer arithmetic on them possible, although they can easily be (and in fact implicitly are) converted to and from any other object pointer type.

[edit] Arrays

Array types in C are always one-dimensional and, traditionally, of a fixed, static size specified at compile time. (The more recent "C99" standard also allows a form of variable-length arrays.) However, it is also possible to allocate a block of memory (of arbitrary size) at run-time, using the standard library's malloc function, and treat it as an array. C's unification of arrays and pointers (see below) means that true arrays and these dynamically-allocated, simulated arrays are virtually interchangeable. Since arrays are always accessed (in effect) via pointers, array accesses are typically not checked against the underlying array size, although the compiler may provide bounds checking as an option. Array bounds violations are therefore possible and rather common in carelessly written code (see the "Criticism" article), and can lead to various repercussions: illegal memory accesses, corruption of data, buffer overrun, run-time exceptions, etc.

C does not have a special provision for declaring multidimensional arrays, but rather relies on recursion within the type system to declare arrays of arrays, which effectively accomplishes the same thing. The index values of the resulting "multidimensional array" can be thought of as increasing in row-major order.

[edit] Array↔pointer interchangeability

A distinctive (but potentially confusing) feature of C is its treatment of arrays and pointers. The array-subscript notation x[i] can also be used when x is a pointer; the interpretation (using pointer arithmetic) is to access the (i+1)th of several adjacent data objects pointed to by x, counting the object that x points to (which is x[0]) as the first element of the array.

Formally, x[i] is equivalent to *(x + i). Since the type of the pointer involved is known to the compiler at compile time, the address that x + i points to is not the address pointed to by x incremented by i bytes, but rather incremented by i multiplied by the size of an element that x points to. The size of these elements can be determined with the operator sizeof by applying it to any dereferenced element of x, as in n = sizeof *x or n = sizeof x[0].

Furthermore, in most expression contexts (a notable exception is sizeof array), the name of an array is automatically converted to a pointer to the array's first element; this implies that an array is never copied as a whole when named as an argument to a function, but rather only the address of its first element is passed. Therefore, although C's function calls use pass-by-value semantics, arrays are in effect passed by reference.

The number of elements in an array a can be determined as sizeof a / sizeof a[0], provided that the name is "in scope" (visible).

An interesting demonstration of the interchangeability of pointers and arrays is shown below. The four assignments are equivalent and each is valid C code. Note how the last line contains the strange code i[x] = 1;, which has the index variable i apparently interchanged with the array variable x. This last line might be found in obfuscated C code.

/* x designates an array */
x[i] = 1;
*(x + i) = 1;
*(i + x) = 1;
i[x] = 1; /* strange, but correct */

However, there is a distinction to be made between arrays and pointer variables. Even though the name of an array is in most expression contexts converted to a pointer (to its first element), this pointer does not itself occupy any storage. Consequently, you cannot change what an array "points to", and it is impossible to assign to an array. (Arrays may however be copied using the memcpy function, for example.)

[edit] Memory management

One of the most important functions of a programming language is to provide facilities for managing memory and the objects that are stored in memory. C provides three distinct ways to allocate memory for objects:

Static memory allocation: space for the object is provided in the binary at compile-time; these objects have an extent (or lifetime) as long as the binary which contains them is loaded into memory
Automatic memory allocation: temporary objects can be stored on the stack, and this space is automatically freed and reusable after the block in which they are declared is exited
Dynamic memory allocation: blocks of memory of arbitrary size can be requested at run-time using library functions such as malloc from a region of memory called the heap; these blocks can be subsequently freed for reuse by calling the library function free

These three approaches are appropriate in different situations and have various tradeoffs. For example, static memory allocation has no allocation overhead, automatic allocation has a small amount of overhead during initialization, and dynamic memory allocation can potentially have a great deal of overhead for both allocation and deallocation. On the other hand, stack space is typically much more limited and transient than either static memory or heap space, and dynamic memory allocation allows allocation of objects whose size is known only at run-time. Most C programs make extensive use of all three.

Where possible, automatic or static allocation is usually preferred because the storage is managed by the compiler, freeing the programmer of the potentially error-prone hassle of manually allocating and releasing storage. Unfortunately, many data structures can grow in size at runtime; since automatic and static allocations must have a fixed size at compile-time, there are many situations in which dynamic allocation must be used. Variable-sized arrays are a common example of this (see "malloc" for an example of dynamically allocated arrays).

[edit] Libraries

The C programming language uses libraries as its primary method of extension. In C, a library is a set of functions contained within a single "archive" file. Each library typically has a header file, which contains the prototypes of the functions contained within the library that may be used by a program, and declarations of special data types and macro symbols used with these functions. In order for a program to use a library, it must include the library's header file, and the library must be linked with the program, which in many cases requires compiler flags (e.g., -lm, shorthand for "math library").

The most common C library is the C standard library, which is specified by the ISO and ANSI C standards and comes with every C implementation. ("Freestanding" [embedded] C implementations may provide only a subset of the standard library.) This library supports stream input and output, memory allocation, mathematics, character strings, and time values.

Another common set of C library functions are those used by applications specifically targeted for Unix and Unix-like systems, especially functions which provide an interface to the kernel. These functions are detailed in various standards such as POSIX and the Single UNIX Specification.

Since many programs have been written in C, there are a wide variety of other libraries available. Libraries are often written in C because C compilers generate efficient object code; programmers then create interfaces to the library so that the routines can be used from higher-level languages like Java, Perl, and Python.

[edit] Criticism

Main article: Criticism of the C programming language

Despite its popularity, C has been widely criticized. Such criticisms fall into two broad classes: desirable operations that are too hard to achieve using unadorned C, and undesirable operations that are too easy to accidentally achieve while using C. Putting this another way, the safe, effective use of C requires more programmer skill, experience, effort, and attention to detail than is required for some other programming languages.

[edit] Tools for mitigating issues with C

Tools have been created to help C programmers avoid some of the problems inherent in the language.

Automated source code checking and auditing are beneficial in any language, and for C many such tools exist, such as Lint. A common practice is to use Lint to detect questionable code when a program is first written. Once a program passes Lint, it is then compiled using the C compiler.

There are also compilers, libraries and operating system level mechanisms for performing array bounds checking, buffer overflow detection, serialization and automatic garbage collection, that are not a standard part of C.

Cproto is a program that will read a C source file and output prototypes of all the functions within the source file. This program can be used in conjunction with the "make" command to create new files containing prototypes each time the source file has been changed. These prototype files can be included by the original source file (e.g., as "filename.p"), which reduces the problems of keeping function definitions and source files in agreement.

It should be recognized that these tools are not a panacea. Because of C's flexibility, some types of errors involving misuse of variadic functions, out-of-bounds array indexing, and incorrect memory management cannot be detected on some architectures without incurring a significant performance penalty. However, some common cases can be recognized and accounted for.

Computer Network

2007-05-10T02:55:00.000-07:00

A computer network is multiple computers connected together using a telecommunication system for the purpose of communicating and sharing resources.
Experts in the field of networking debate whether two computers that are connected together using some form of communications medium constitute a network. Therefore, some works state that a network requires three connected computers. For example, "Telecommunications: Glossary of Telecommunication Terms" states that a computer network is "A network of data processing nodes that are interconnected for the purpose of data communication", the term "network" being defined in the same document as "An interconnection of three or more communicating entities". A computer connected to a non-computing device (e.g., networked to a printer via an Ethernet link) may also represent a computer network, although this article does not address this configuration.
This article uses the definition which requires two or more computers to be connected together to form a network. The same basic functions are generally present in this case as with larger numbers of connected computers.

Basics
A computer network may be described as the inteconnection of two or more computers that may share files and folders, applications, or resources like printers,scanners,webcams etc. Internet is also a type of computer network which connects all the computers of the world having Internet facility on them.

Protocols
Main article: Protocols
A protocol is a set of rules and conventions about the communication in the network. A protocol mainly defines the following:
Syntax: Defines the structure or format of data.
Semantics: Defines the interpretation of data being sent.
Timing: Refers to an agreement between a sender and a receiver about the transmission.

Standards Organisations
Various standards organisations for data communication exist today. They are broadly classified into three categories:
Standards Creation Committees.
Forums
Regulatory Agencies

Standards Creation Committees
Some important organisations in this category are:
International Organization for Standardization (ISO; also known as International Standards Organisation)
A multinational standards body
International Telecommunications Union - Telecommunication Standards Sector (ITU-T)
Previously, CCITT. Developed under United Nations for national standards.
American National Standards Institute (ANSI)
An affiliate of ITU-T
Institute of Electrical and Electronic Engineers (IEEE)
Largest professional engineering body in the world. Oversees the development and adoption of international electrical and electronic standards.
Electronic Industries Alliance (EIA; formerly Electronic Industries Association)
Aligned with ANSI. Focuses public awareness and lobbying for standards.

Forums
University students, user groups, industry representatives and experts come together and set up forums to address various issues and concerns of data communication technology and come up with standards for the day's need. Some of the well-known forums are:
The Internet Society(ISOC)
Internet Engineering Task Force (IETF)
Frame Relay Forum
ATM Forum
ATM Consortium

Regulatory Agencies
These are government appointed agencies like Federal Communications Commission (FCC).

Communication Techniques
Data is transmitted in the form of electrical signals. The electrical signals are of two types viz., analog and digital. Similarly, data can also be either analog or digital. Based on them, data communication may be of following types:
Analog data, analog transmission
e.g.: transmission of voice signals over telephone line
Analog data, digital transmission
e.g.: transmission of voice signal after digitisation using PCM, delta modulation or adaptive delta modulation
Digital data, analog transmission
e.g.: communication using modem
Digital data, digital transmission
e.g.: most of present day communication

Modes Of Data Transmission
Digital data can be transmitted in a number of ways:
Parallel and serial communication
Synchronous, iso-synchronous and asynchronous communication
Simplex, half-duplex and full-duplex communication

Transmission Errors
It is virtually impossible to send any signal, analog or digital, over a distance without any distortion even in the most perfect conditions due to:
Delay Distortion
Signals of varying frequencies travel at different speeds along the medium. The speed of travel of a signal is highest at the center of the bandwidth of the medium and lower at both the ends. Therefore, at the receiving end, signals with different frequencies in the given medium will arrive at different times causing delay error.
Attenuation
As a signal travels through a medium, its signal strength decreases.
Noise
A signal travels as an electromagnetic signal through any medium. Electromagnetic energy that gets inserted somewhere during transmission is called noise.
Many attempts have been made to detect and rectify the transmission errors. Error detection schemes:
Vertical Redundancy Check (VRC) or Parity Check
Longitudinal Redundancy Check (LRC)
Cyclic Redundancy Check (CRC)
Error correction schemes:
stop-and-wait
go-back-n
sliding-window

Building a computer network
A simple computer network may be constructed from two computers by adding a network adapter (Network Interface Controller (NIC)) to each computer and then connecting them together with a special cable called a crossover cable. This type of network is useful for transferring information between two computers that are not normally connected to each other by a permanent network connection or for basic home networking applications. Alternatively, a network between two computers can be established without dedicated extra hardware by using a standard connection such as the RS-232 serial port on both computers, connecting them to each other via a special crosslinked null modem cable.
Practical networks generally consist of more than two interconnected computers and generally require special devices in addition to the Network Interface Controller that each computer needs to be equipped with. Examples of some of these special devices are listed above under Basic Computer Network Building Blocks / networking devices.

Types of networks:
Below is a list of the most common types of computer networks.

A personal area network (PAN) :
A personal area network (PAN) is a computer network used for communication among computer devices (including telephones and personal digital assistants) close to one person. The devices may or may not belong to the person in question. The reach of a PAN is typically a few meters. PANs can be used for communication among the personal devices themselves (intrapersonal communication), or for connecting to a higher level network and the Internet (an uplink).
Personal area networks may be wired with computer buses such as USB and FireWire. A wireless personal area network (WPAN) can also be made possible with network technologies such as IrDA and Bluetooth.

Local Area Network (LAN):
A network that is limited to a relatively small spatial area such as a room, a single building, a ship, or an aircraft. Local area networks are sometimes called a single location network.
Note: For administrative purposes, large LANs are generally divided into smaller logical segments called workgroups. A workgroup is a group of computers that share a common set of resources within a LAN.

Campus Area Network (CAN):
A network that connects two or more LANs but that is limited to a specific (possibly private) geographical area such as a college campus, industrial complex, or a military base
Note: A CAN is generally limited to an area that is smaller than a Metropolitan Area Network.

Metropolitan Area Network (MAN):
A network that connects two or more Local Area Networks or CANs together but does not extend beyond the boundaries of the immediate town, city, or metropolitan area. Multiple routers, switches & hubs are connected to create a MAN

Wide Area Networks (WAN):
A WAN is a data communications network that covers a relatively broad geographic area and that often uses transmission facilities provided by common carriers, such as telephone companies. WAN technologies generally function at the lower three layers of the OSI reference model: the physical layer, the data link layer, and the network layer.
Types of WANs:
Centralized:
A centralized WAN consists of a central computer that is connected to dumb terminals and / or other types of terminal devices.
Distributed:
A distributed WAN consists of two or more computers in different locations and may also include connections to dumb terminals and other types of terminal devices.

Internetwork:
Two or more networks or network segments connected using devices that operate at layer 3 (the 'network' layer) of the OSI Basic Reference Model, such as a router.
Note: Any interconnection among or between public, private, commercial, industrial, or governmental networks may also be defined as an internetwork.
Internet, The:
A specific internetwork, consisting of a worldwide interconnection of governmental, academic, public, and private networks based upon the Advanced Research Projects Agency Network (ARPANET) developed by ARPA of the U.S. Department of Defense – also home to the World Wide Web (WWW) and referred to as the 'Internet' with a capital 'I' to distinguish it from other generic internetworks.

Intranet:
A network or internetwork that is limited in scope to a single organization or entity or, also, a network or internetwork that is limited in scope to a single organization or entity and which uses the TCP/IP protocol suite, HTTP, FTP, and other network protocols and software commonly used on the Internet.
Note: Intranets may also be categorized as a LAN, CAN, MAN, WAN, or other type of network.

Extranet:
A network or internetwork that is limited in scope to a single organization or entity but which also has limited connections to the networks of one or more other usually, but not necessarily, trusted organizations or entities (e.g., a company's customers may be provided access to some part of its intranet thusly creating an extranet while at the same time the customers may not be considered 'trusted' from a security standpoint).
Note: Technically, an extranet may also be categorized as a CAN, MAN, WAN, or other type of network, although, by definition, an extranet cannot consist of a single LAN, because an extranet must have at least one connection with an outside network.
Intranets and extranets may or may not have connections to the Internet. If connected to the Internet, the intranet or extranet is normally protected from being accessed from the Internet without proper authorization. The Internet itself is not considered to be a part of the intranet or extranet, although the Internet may serve as a portal for access to portions of an extranet.
Classification of computer networks

This article or section does not cite any references or sources.Please help improve this article by adding citations to reliable sources. (help, get involved!)Any material not supported by sources may be challenged and removed at any time. This article has been tagged since December 2006.

By network layer
Computer networks may be classified according to the network layer at which they operate according to some basic reference models that are considered to be standards in the industry such as the seven layer OSI reference model and the five layer TCP/IP model.

By scale
Computer networks may be classified according to the scale or extent of reach of the network, for example as a Personal area network (PAN), Local area network (LAN), Campus area network (CAN), Metropolitan area network (MAN), or Wide area network (WAN).

By connection method
Computer networks may be classified according to the technology that is used to connect the individual devices in the network such as HomePNA, Power line communication, Ethernet, or Wireless LAN.

By functional relationship
Computer networks may be classified according to the functional relationships which exist between the elements of the network, for example Active Networking, Client-server and Peer-to-peer (workgroup) architectures. Also, computer networks are used to send data from one to another by the hardrive

By network topology
Computer networks may be classified according to the network topology upon which the network is based, such as Bus network, Star network, Ring network, Mesh network, Star-bus network, Tree or Hierarchical topology network, etc.
Topology can be arranged in a Geometric Arragement

By services provided
Computer networks may be classified according to the services which they provide, such as Storage area networks, Server farms, Process control networks, Value-added network, Wireless community network, etc.

By protocol
Computer networks may be classified according to the communications protocol that is being used on the network. See the articles on List of network protocol stacks and List of network protocols for more information.

See also
Computer networking
Computer networking device
Wireless network
Node (networking)
Network topology
Expander graph
Scale-free network
Network diagram
Internet
History of the Internet

E-books links

2007-05-10T02:51:00.000-07:00

C Optimization Tutorial
Compiling C and C++ Programs on UNIX Systems - gcc/g++
Building and Using Static and Shared C Libraries
Programming in C: UNIX System Calls and Subroutines Using C Programming
C FAQ
C Programming Class Notes
ANSI C for Programmers on UNIX Systems
Sams Teach Yourself C in 24 Hours
Sams Teach Yourself C in 21 Days (4th Ed.)
The Standard C Library for Linux - Part 1: file functions
The Standard C Library for Linux - Part 2: character input/output
The Standard C Library for Linux - Part 3: formatted input/output
The Standard C Library for Linux - Part 4: Character Handling
The Standard C Library for Linux - Part 5: Miscellaneous Functions
Programming in C: A Tutorial
An Introduction to C Development on Linux
C Programming Course
C Language Tutorial
CScene: An Online Magazine for C and C++ Programming
C++ Tutorial
Understanding C++: An Accelerated Introduction
An Introduction to C++ Class Hierarchies
G++ FAQ
Introduction to Object-Oriented Programming Using C++
Compiling C and C++ Programs on UNIX Systems - gcc/g++
C++ FAQ Lite
C++ Programming Language Tutorials
Reducing Dependencies in C++
C++ Exception Handling
Part 1: Unicode
Part 2: A Complete String Class
Making C++ Loadable Modules Work
Sams Teach Yourself C++ in 21 Days (2nd Ed.)
C++ Portability Guide
C++ Tips
C++ Language Tutorial
CScene: An Online Magazine for C and C++ Programming
C++ Libraries FAQ
Enterprise JavaBeans Tutorial
JavaBeans Short Course
Introduction to the JavaBeans API
JDBC Short Course
Essentials of the Java Programming Language, Part 1
Essentials of the Java Programming Language, Part 2
Writing Advanced Applications for the Java Platform
Fundamentals of Java Security
Fundamentals of Java Servlets
Introduction to the Collections Framework
Introduction to CORBA
Fundamentals of RMI
Advanced
Introductory
Intermediate
Java Language Specification
Java Tutorial: Servlet Trail
Java Virtual Machine Specification (2nd Ed.)
Glossary of Java and Related Terms
The Java Language Environment
Java Look and Feel Design Guidelines
Story of a Servlet: An Instant Tutorial
Introduction to Java
Java2D: An Introduction and Tutorial
Java Servlet Tutorial
comp.lang.java FAQ
Brewing Java: A Tutorial
Shlurrrppp ... Java: The First User-Friendly Tutorial on Java
Swing Tutorial
Swing: A Quick Tutorial for AWT Programmers
Thinking in Java
Java RMI Tutorial
Java for C++ Programmers
The Advanced Jav/aJ2EE Tutorial
Hacking Java: The Java Professional's Resource Kit
JFC Unleashed
Java Developer's Guide
Java Developer's Reference
Sams Teach Yourself Java in 21 Days (Professional Reference Ed.)
Java Unleashed (2nd Ed.)
Java 1.1 Unleashed (3rd Ed.)
Java Game Programming Tutorial
Java Networking FAQ
HTML Table Tutorial
HTML by Example
How to Use HTML 3.2
Creating a Client-Side Image Map
Advanced HTML: How to Create Complex Multimedia Documents for the Web
The ABCs of HTML
Sharky's Netscape Frames Tutorial
A Tutorial for Perl GIMP Users
A Scheme Tutorial for GIMP Users
GIMP Guide
The GIMP User Manual
Pseudo 3-D with GIMP
Graphical Photocomposition with GIMP
Creating Text with the GIMP
Creating Fire Effects with the GIMP
Creating and Editing Animations with GIMP
GIMP-Perl: GIMP Scripting for the Rest of Us
Writing a GIMP Plugin
GIMP: The RRU Tutorial
GIMP User FAQ
Script-Fu Tutorial
The Quick Start Guide to the GIMP, Part 1
The Quick Start Guide to the GIMP, Part 2
The Quick Start Guide to the GIMP, Part 3
The Quick Start Guide to the GIMP, Part 4
Part 1: Everything You Need to Get Started
Part 2: Building a Sample Genealogy Program
Part 3: Adding File Saving and Loading Using libxml
Creating GTK+ Widgets with GOB: An Easier Way to Derive New GTK+ Widgets
Handling Multipel Documents: Using the GnomeMDI Framework
Livening Things Up: Graphics Made Easy Using the GNOME Canvas
Developing Gnome Applications with Python - Part 1
GLib Reference Manual
GTK+ Reference Manual
The GIMP Toolkit
GTK+ FAQ
GTK V1.2 Tutorial
Drawing and Event Handling in GTK
An Introduction to the GIMP Tool Kit
Continuum Dynamics
Differential Equation Basics
Energy Functions and Stiffness
Particle System Dynamics
An Introduction to Physically Based Modeling
Rigid Body Dynamics I
Rigid Body Dynamics II
Scientific Visualization Tutorials
Gnuplot - An Interactive Plotting Program
GIF Animation Tutorial
Professional Programmer's Guide to Fortran 77
Fortran 90 and Computational Science
User Notes on Fortran Programming
Fortran Programming for Physics and Astronomy
A Fortran 90 Tutorial
Using GNU Fortran
Fortran 90: A Course for Fortran 77 Programmers
Fortran 90 for the Fortran 77 Programmer
Introduction to Fortran

How to prepare for MBA ??

2007-05-10T02:42:00.001-07:00

While our politicians are busy debating on whether India is shining or not, there is one career that has been glittering for quite some time now. It is post-graduation in management, or MBA.What exactly is an MBA? Why is it so sought after? And most importantly, who can get there? How?The Masters in Business Administration (MBA) is offered under various names such as PGDBA, MMS, PGDBM etc.The programme is designed to enable a student to handle managerial level responsibilities in an organisation. Since managerial skills are many, most institutes allow a student to specialise in a set of skills related to a particular area of operation.Common specialisations offered are Finance, Marketing, Human Resource Management, Systems, etc. Finance and Marketing have been evergreen areas, and almost 75 per cent of MBAs belong to one of these two fields. Systems and Operations are some of the more recent options for engineers, and HRM is an upcoming career.The most obvious reason MBA programmes attract so many candidates is the high starting salaries coupled with respectable positions in reputed companies. And best of all, you get a job even before you have completed the course (assuming the institute is among the top 15 or so).All this in just two years, and if our HRD minister has his way, for just Rs 60,000! Which, compared to average starting salaries of around Rs 6 lakh per year, is a pittance.Can anybody pursue an MBA? Well, the primary criterion is that you should be a graduate (students in final year can also apply, since they graduate by the time the admission process is over).It does not matter what you graduate in. It does not matter whether it is full-time or correspondence, and even your academic record is not a pre-condition for applying (though a few institutes insist on at least 50 per cent marks, and almost all of them would attach some importance to your marks at the second stage).However, you need good aptitude, as this is the first step in testing and shortlisting candidates. The aptitude test, which is a multiple choice written test, usually tests Quantitative, Verbal and Logical skills. Some institutes also test General Awareness.Time is a constraint and one needs to have sharp thinking skills. A majority of candidates get eliminated in the first round itself, but this fact should not deter you from trying.If you have the determination, you will succeed. After all, about 2,000 candidates do make it to one of the top institutes every year.The second stage of selection involves an interaction with the candidate.This is done in the form of Group Discussions and Personal Interviews (GDs and PIs). These allow the panelists to assess your overall personality, your communication skills, your potential to handle managerial responsibilities etc.This is a crucial stage in the selection as there is elimination in this round as well. Most institutes then give a certain weightage to the various factors such as the written test score, GD and PI scores, academic record, and work experience, if any. The final overall score is then computed, and admission offers made.If one were to profile candidates selected to top management institutes over the years, one would see a healthy blend of students belonging to all fields of graduation, the most common being engineering, commerce, arts and science. There are also a few doctors and quite a few CAs. There are students with no work experience, with 1-2 years of work experience and even a few with 5-10 years of work experience.What’s common to all of them is a strong desire to pursue their dreams and a determination to succeed. This is what drives them. This is what will drive you.

Joining a Medical College after your Entrance Examination

2007-05-10T02:38:00.000-07:00

Joining a Medical College after your Entrance Examination
1. Scholarship
Ministry of Education (MOE)
Institute of Medicine (IOM)
B. P. Koirala Institute of Health Sciences
Kathmandu University Affiliated Medical CollegesEmbassy2. Non Scholarship
TU Affiliated Medical Colleges
B. P. Koirala Institute of Health Sciences (BPKIHs)
Kathmandu Univesity Medical Entrance Test (KUMET)3. Abroad [break=Scholarship]1. ScholarshipMinistry of Education (MOE)If you have got through the MOE, choose the medical college that you are likely to get and think about your choice. Apply for the scholarship whenever the colleges do demand for the students from the MOE. Then get it done i.e. go admit. You should always be vigilant once you find yourself in the likelihood of merit list of MOE. Otherwise your dream and hard work will just evaporate under your nose. Never take rest.If you are in higher merit list discuss a lot and choose an appropriate medical college. We advise you to study in Nepal.Institute of Medicine (IOM)Getting through the entrance examination is the sweetest part in itself but don't forget to note the date of admission and its criteria i.e. Duration, amount of money, testimonials you have to submit, prophylactic medication that you have to take etc. Get it done and take long breath. If your name is published in the notice board as a successful candidate find out last date for admission and get it done within defined time frame. Celebrate yourself you know your mind need rewards too. That's the way you should live in life.B. P. Koirala Institute of Health SciencesIts the same, your are in get admission form. Once you join the college try to be in touch with other medical students in nepal or in abroad. Medicine is an art which flourish with sharing experiences.Kathmandu University Affiliated Medical CollegesAll the KU affiliate colleges take the students from the merit list of entrance examination of MOE. Get vigilant with the MOE's result, your position and the session of the college that are going to take the students. Apply accordingly and take admission. Sometimes, the students get confused and miss the chance! Don't let that accident happen to you. Usually 10% or 20% of total medical seat available in college is for MOE candidates if college is run by Nepali Citizen or Foreigner respectively.EmbassyThis is particularly about the Indian Embassy because they good number of seats and conduct their own entrance examination each year. Once you take the entrance examination of Indian Embassy and are in the top ten lists. Your job should be to contact embassy daily if not in every alternate days otherwise you will find yourself in jeopardy and whole hard work in vain. It will be of course tough to get to the point of college admission in India .[break=Non Scholarship]2. Non ScholarshipTU Affiliated Medical Colleges First of all, appear the Entrance Examination conducted by the IOM. It publishes the result within a week. But you must pass the exam (score 50% i.e. 75 marks) to apply for the colleges affiliated to the TU. Take the score and apply for the seat in different TU affiliated colleges where you want to study. The final decision is in the hand of college.B. P. Koirala Institute of Health Sciences (BPKIHs) It is same as that of the Scholarship Scheme.Kathmandu Univesity Medical Entrance Test (KUMET)All the KU affiliate colleges take the students from the merit list of entrance examination of KUMET. Get vigilant with the KUMET's result, your grading list (A, B or C) and the session of the college that are going to take the students. Apply accordingly and take admission. Sometimes, the students get confused and miss the chance! Don't let that accident happen to you. you know one thing those who are successful in IOM, BPKIHS or even MOE they are sure that they will become doctor one day. But it might not be so for few candidates as you have to go through the individual interviews conducted by respective medical colleges affiliated to KU and more over there is fewer medical seats than the no. of candidates pass their KUMET. Many of the medical colleges now are looking for SLC score, ISc/+2 marks, ECA (Extracurricular Activities), your way of thinking and above all one of the most preferred question in the interview is - Why do you want to join medical college? or Why did you choose medicine as your profession? or Why do you want to be a doctor? so get prepared for the interview. And above all its money, prepare for the ransom amount you will pay to the medical college. Most of the medical colleges prefer those type of candidates who pay all the tuition fees this is the most effective way to get into a medical college after your KUMET.[break=Abroad]3. Abroad For SAARC, NON-SAARC all the jobs are done by the agency. However, it is your career and interest in medicine, so get serious and know about the procedures and your needs from the knowledgeable persons.

How to prepare for Engineering ??

2007-05-10T02:37:00.001-07:00

Entrance tests like the IIT-JEE, AIEEE and K-CET are round the corner. Here are some useful tips to keep in mind before taking the papers.An engineering degree after Class 12/PUC is one of the most widely sought after study options. The versatility of an engineering degree and the good job opportunities after completing one are the main reasons for the high demand for engineering courses all across the country. To cater to this demand, a large number of engineering colleges have opened up all across the country in the last decade or so. These colleges vary vastly in terms of the quality of education they provide to their students. Consequently, career opportunities for engineering graduates also vary vastly depending on the quality of the engineering college from where they graduate. In a country which produces lakhs of engineers every year, being �just an engineer� hardly matters. What matters is where you did you engineering from. It is important and imperative for all students and parents to understand the admission process for engineering courses and a few basic details about important entrance exams in the country.There are three levels of entrance exams � each deciding admission into a different category of engineering colleges.Level 1: IIT- JEEThere are seven Indian Institute of Technology (IITs) in India located at Mumbai, Chennai, Delhi, Kanpur, Kharagpur, Gauhati and Roorkee. These are without any doubt the best engineering colleges in the country. The rich history, brilliant infrastructure, good faculty, excellent international reputation and good performance of alumni contribute to making these institutions the most sought after engineering colleges in the country. Entry into these institutions is extremely competitive. The IITs conduct a Joint Entrance Examination (JEE) every year to decide which students they will admit into their institutions. Apart from the IITs, the JEE scores are also used by two other institutions, namely IT�BHU and ISM Dhanbad. All these institutes together have about 4,600 seats. Over 150,000 engineering aspirants write this examination every year. This examination is conducted in two parts: the screening exam and the main exam. Only those students who clear the screening examination can appear for the main exam. The screening exam is a three-hour multiple choice question paper covering Physics, Chemistry and Mathematics. The paper consists of 84 questions - 28 from each subject. Each question carries three marks. A student loses one mark for every wrong answer hence, guess work should be avoided. Apart from testing the conceptual knowledge of a student, the questions also test the ability to apply the various concepts to practical situations. Simple formula-oriented problems are almost never asked at the JEE. Answer choices tend to be close and can often mislead a student. This year, about 19,000 students were short listed to write the main examination. The main examination comprises of three separate two-hour long descriptive exams in Physics, Chemistry and Mathematics. The exam in all the three subjects are conducted on a single day. For the year 2004, each paper contained ten questions of two marks each and ten questions of four marks each. There is no negative marking and marks are also given for the logical approach followed while solving the problem. In year 2005, the screening and the main exams will be conducted on April 10, 2005 and May 22, 2005 respectively. The JEE is the most challenging engineering entrance examination in the country. It requires a lot of hard work and dedication to get through this exam. A preparation over a period of two years would be recommended to prepare for this exam. The preparation should commence immediately after a student completes his/her SSLC/Class X examination.Level 2 : AIEEEThe All India Engineering Entrance Examination (AIEEE) was introduced in the year 2002. This examination is conducted by the CBSE and held in May every year. Admission to all the 17 National Institute of Technology (NITs) in the country earlier known as Regional Engineering Colleges (RECs) is also through this examination only. This year, about 430,000 students took up the AIEEE exam all across the country. Including the NITs, the number of institutions using the AIEEE scores to shortlist their final list of candidates is in excess of 100. More than 11,000 seats are up for grabs through this examination.A large number of reputed deemed universities like Birla Institute of Technology (Mesra), Manipal Academy of higher Education (Manipal), Sathyabama Institute of Science and Technology (Chennai), Vellore Institute of Technology (Vellore), etc. participate in the AIEEE every year. The number of good quality institutes participating in this exam is quite high and hence it becomes a very critical exam in the engineering aspirants� calendar.The AIEEE is an objective examination. The examination is based on the NCERT syllabus of class XI and XII in the subjects of Physics, Chemistry and Mathematics. It consists of two papers: (1) Paper 1: A 2 � hour long paper on Physics and Chemistry, where 75 multiple choice questions are asked from each subject. (2) Paper 2: A 1 � hour long paper containing 75 questions in Mathematics. Both these papers are conducted on the same day. For the year 2005, the AIEEE will be conducted on the May 8. Each question carries three marks. One mark is deducted for every wrong answer. Hence, wild guessing should be avoided. In Karnataka the exam is conducted at Bangalore, Davangare, Gulbarga, Hubli and Mangalore. The notification for this examination has already been issued and the last date to submit the application form is on February 4, 2005. Since the competition through this exam is tough, an aspiring engineer would be advised to prepare for this exam over a period of two years.Level 3: State Entrance Exams (K-CET)At the third level, we have the various engineering colleges in the state affiliated to the Visveswariah Technological University (VTU) and Bangalore University. The entry into these colleges is based on the performance of the student in the board examination for class XII and the Common entrance test with 50 per cent weightage given to each. The CET is normally held in the month of May. An aspiring engineer has to answer objective exams in the subjects of Physics, Chemistry and Mathematics.Each exam is of 1 � hour duration and 60 multiple choice questions have to be answered. A right answer earns a student one mark. For every wrong answer � of a mark is deducted. Some of the prominent engineering colleges in the state which admit students through the CET examination are UVCE-Bangalore, PESIT, BMS College of Engineering, M.S Ramaiah Institute of Technology, RVCE, etc.If we look at the trend across the country, the importance of national level entrance exams like IIT-JEE and AIEEE is increasing year after year. The increasing importance of IIT-JEE is understandable � with the increasing recognition the IITians are getting the world over is making many engineering aspirants burn the midnight oil in trying to get into the hallowed portals of the IITs, some of the best institutes in the world.Let us understand the reason for the increasing importance of AIEEE. The number of engineering colleges in various States is going up every year. The selection into these colleges is through State level entrance exams in most States in the country. However, with the increasing number of colleges and the consequent increase in the number of seats available to students, the relevance of the State level entrance exams is coming down. In fact, in a few States, in the last two years, many engineering colleges had seats to offer but no students to take admission.Add to this the fantastic placement in IITs and NITs � the difference becomes crystal clear. In this scenario, unless students aim for the best colleges � the IITs and the NITs � they will not be able to ensure a good career for themselves. Parents should also understand this and accordingly guide their children in their preparation.A lot of parents push their children towards the state level entrance exams only � at the cost of national level entrance exams. They should not forget that preparing for national level entrance exams like IIT-JEE and AIEEE will anyway help the students do well in the State level entrance exams also.

How to prepare for GRE ??

2007-05-10T02:35:00.000-07:00

GUIDE TO PREPARE FOR THE GRE STANDARDIZED ADMISSIONS EXAMPreparing to Take the GRE Graduate School Test.Format of The Gre Verbal Section - The GRE verbal sections consist of four types of questions: Sentence Completions, Analogies, Reading Comprehension, and Antonyms. They are designed to test your ability to reason using the written word. The section is 30 minutes long and contains 30 questions. The questions can appear in any order.Format of The Gre Writting Section - The analytical writing section is 75 minutes long and requires you to respond to two essay questions. The Present Your Perspective on an Issue essay comes first and is 45 minutes long. Then the Analyze an Argument essay is presented and is 30 minutes long.What does it mean for a test to be adaptive? : -This is an excellent question, and as with all aspects of life, it is quite useful to know the lay of the land. A basic part of a CAT is that it does not give equal weight to each question that you answer. As the registration materials from ETS suggest, the difficulty level of the questions you answer is factored into how much they count toward your score. Yet, it is important to clarify what this means in order to optimize your score when you are taking the test. The adaptive part of CAT means that the computer is assessing who you are from the very first question that you answer. Based on your performance on the prior question, the computer will give you a new question that responds to what it considers to be the appropriate difficulty level for you.Strategies for the GRE :- Most international students have a difficult time with the verbal sections of the GRE. Here is some information and strategies to assist you with this challenging exam. On the GRE verbal section, you'll encounter four different question types.What's The Score? - Educational Testing Service, the makers of the GRE, indicate time management as the key to success. Your timing skills could add or subtract 100 points from your score. However, there are many theories on the best ways to prepare for the GRE, and a number of websites, books, and even CD-ROMS, cover plenty of material including sample questions, to keep students well-informed, and well preparedAdvice on the GRE from The Princeton Review - The articles and information on this page will help you find your way along the road to graduate school, and to acing your GRE.Five Steps to Take BEFORE You Study for the GRE - As a GRE prep course instructor, I've often wished I could catch students two months before the class starts and give them a list of things to do before they even begin studying. Here is what would be on that list.Test Tactics and Sectional Strategies for the GRE-The suggestions and advice offered here are drawn from the set of decks of GRE flash cards offered by Oakwood Publishing Company, designed to help you achieve a higher score on your GRE. GRE is a registered trademark of the Educational Testing Service, which was not involved in the production of, and does not endorse, these study cards.One Mean CAT-To quote ETS, the makers of the GRE, "Time management is key." Your timing skills could add or subtract 100 points from your score. Timing skills are important because the CAT has unusual pacing constraintsGRE Acronyms Madness - If grad school is in your future, you most likely know that a standardized test is an unavoidable part of the application process. Unlike applying to college in which you had to only take one test, the SAT (or ACT), you now have to decipher a plethora of acronyms to successfully navigate the grad admissions process. Obviously, it's easy to become confused. The following is a guide to all the acronyms you may encounter:Graduate Record Exam-Site provides general information about the GRE; info about their own excellent test-prep materials; financing grad school; links to other resources; reviews of recent Graduate Record Exams. Includes a section on CAT Strategies telling how to effectively approach the Computer Adaptive Test. Take a sample test (choose from GRE, GMAT, LSAT, SAT, USMLE, etc.) requires FREE registration. Princeton ReviewHow You Can Achieve Higher Scores For Higher Education - Just how important in the admissions process are your scores on admissions tests? On balance, a high score may not get you in There, but a low score may keep you out.Test Pacer: Pacing for the GRE -Pacing strategies are more critical and difficult on the GRE CAT (computer-adaptive test) than for any test you have ever taken. To quote the makers of the GRE, "Time management is key." Your timing skills could add or subtract 100 points from your score. This is because the test has highly unusual pacing constraints.GRE General Vocabulary - study these 1160 words to improve your chances of scoring high on the verbal section of GRE General test. Don't learn spelling, don't try to learn all the word meanings - only the short definitions given here. Be sure to check Vocabulary Workout and Software sections to learn more how to make it easier to memorize such vocabulary.GRE Analogies - An Introduction to Analogies for the GRE Exam.GRE Details: Test Takers -Free, official test preparation materials for the computer- and paper-based GRE® tests are available to anyone who registers for the GRE tests worldwide or who visits this Web site. Other helpful test preparation materials are available for a modest fee.GRE Practice Book Online (PDF) - Download this PDF for sample GRE Test Questions and learn how to prepare for the GRE.GRE Prep Course-Kaplan's comprehensive GRE classroom course or video-based course achieves a perfect balance of intensive review, realistic practice, and integrated online resources. You'll build confidence and valuable test-taking skills through targeted lessons, test-like practice, and dynamic instruction. You CAN score higher on the GRE; just let Kaplan show you how.GRE Strategy and Tips -Barron's provides a GRE high-frequency word list, a 3500-word master vocabulary-building list, and six full-length practice tests. This GRE prep book is definitely worth a look.GRE Test Prep :- Failing to prepare is preparing to fail. GRE preparation should be taken very seriously. If you were one to cram in undergrad school, better step into gear right away. This is no time to wait until the last minute. Like most entrance exams, scores will lie high in determining admission to grad school along with your GPA. If you had a low GPA, your GRE scores will make or break your chances of admission. With adequate GRE preparation, you will feel much better taking the test when you know you fully trained yourself for the taskComputer Based Tests for GRE - The following test preparation instructions, tips, insights, summaries are prepared by test experts who all scored higher than the 99th percentile on the real GRE CBT.Ivy League Admission GRE Test Preparation - Offers quality test preparation resources in a convenient, affordable format, in order to empower all candidates to do their best. Use the following files judiciously to achieve the best score possible!GRE Sentence Completions - In this lesson, we will learn to understand sentence completions. These are the second most coachable questions on the verbal section of the GRE.

GMAT Test Preparation Tips

2007-05-10T02:34:00.000-07:00

You Can Easily Increase Your GMAT CAT Score by 50 to 100 Points
Despite the official statements of ETS (Educational Testing Service), you can improve your GMAT score dramatically simply by taking the time to become "streetwise" about the GMAT CAT. Quite simply, this is the easiest step in your test preparation, and should not be ignored under any circumstances.
Keep in mind that the GMAT is a game. Just as in chess, baseball, tennis, or any other sport, those who know how the game is played have a huge advantage over those who are ignorant of the game's idiosyncratic rules.
As a test taker, you should understand:
The computer-adaptive structure of the GMAT
The types of exam questions asked and their common fallacies
How to manage your time wisely
The computer-adaptive structure of the GMAT
The computer-adaptive test (CAT) version of the GMAT is designed to get a more accurate assessment of your skills while asking you fewer questions than its paper-based predecessor did. Here is how it works: the first question you see in any given section will be of average difficulty. If you get the answer right, your next question will be slightly more difficult. If you get the answer wrong, your next question will be slightly easier. The software will also ask you different types of questions in a rather unpredictable order, as determined by its algorithm, rather than clustering question types as the written GMAT did.
You can not skip a question or go back to an earlier question. Unlike the paper version, once you click the 'answer confirm' box, your answer can not be changed.
The types of exam questions asked and their common fallacies
Examples and explanations of these can be found in the pages describing the individual component sections of the GMAT posted on this website. We strongly encourage our clients to spend time learning these question types before brushing up on their verbal and math skills.
How to manage your time wisely
Practice
The main way to develop GMAT time management skills is to practice taking the test. You will repeatedly see us return to the theme of practice throughout this website. It is very hard to overstate its importance. Therefore you are strongly encouraged to take at least a few mock GMAT exams, in the computer-adaptive format and to try to simulate the actual testing environment. (That means refraining from taking food breaks, engaging in telephone conversations, etc. until you have completed a section.)
Spend adequate time on the first 5 questions
Earlier, we discussed how the GMAT CAT's underlying algorithm determines the difficulty of questions you are asked, based on your performance in answering previous questions. Difficult questions are weighted more heavily in scoring than easier questions. The first couple questions in any GMAT CAT section are used to determine the range of questions that the program 'thinks' you are able to handle. After you have answered these first few questions, the testing software will give you questions to fine tune your score within that rather narrowly predetermined range. Thus, your answers to the first 5 questions will make a HUGE difference in your final section score.
It is imperative that you answer these pivotal questions with extra care. Always double check your answers to these questions. Verify that the answer choices that you judged to be incorrect are indeed incorrect. If you are unsure of the answer to one of these first questions, at the very least, take a very good educated guess using process of elimination.
Prepare yourself to finish the test – at all costs!
There is a huge scoring penalty for failing to finish any section of the GMAT. For example, say you're in line to get a score that will put you in the 70 percentile of test takers, based on your test performance so far – but then run out of time and fail to answer the last five questions in the section. That failure will lower your score to about the 55 percentile. The lesson to take away from this is to prepare yourself to finish the test at all costs. Answering a question incorrectly will hurt you, but not as much as leaving the question unanswered will. Train yourself to work your best within the time limits of the exam. But train yourself, too, to be able to recognize when only a minute or so remains on the clock, and at that point to just answer "C" (or whatever your lucky letter is) for any remaining questions. As the GMAT's Chief Psychometrician put it to us, random guessing is like shooting yourself in the foot – but leaving answers blank is like shooting yourself in both feet.
Don't waste time
This advice probably sounds self evident. However, we mention it because we've had clients tell us how they inadvertently wasted test time by revisiting the help screen or requesting extra scrap paper after they began their test. These activities, if undertaken once the section has begun, will take time away from working on the questions.
Read the Questions Carefully
As silly as this advice may seem, it's worth remembering. An undisciplined test taker will feel the stress of the clock during the timed sections and will try to cut corners to save time, wherever and whenever possible. As a result, he or she often misinterprets questions. GMAT test writers are well aware of this dynamic, and happy to capitalize on it. We guarantee that you will encounter questions on the GMAT that include incorrect answer choices that were deliberately designed to exploit likely misinterpretations of what the question is really asking.
Avoid Random Guessing
The GMAT CAT does not allow you to skip questions and come back to them later, as you can on a written test. You must answer each question on the GMAT CAT before it will allow you to move on to the next question. Consequently, even if you don't know the answer to a particular question, you have to answer it. It is always in your best interest to take an educated guess rather than resorting to random guessing – even if you are running out of time on the section. Usually you will be able to identify at least one answer choice that is clearly wrong. Eliminating even one incorrect choice will improve your odds of answering the question correctly.
Eliminate the Deliberately Deceptive Wrong Choices
With practice, you will begin to learn how to recognize answer choices that are deliberately deceptive – and wrong. There are a few common patterns here that will become apparent as you proceed with your test preparation.
One recognizable pattern is commonly found in the Problem Solving section. It involves an erroneous answer choice giving a value that would result from following a common computational error. You can avoid these deceptive choices by using scrap paper, checking your answers and using estimation to at least judge the general range of the correct choice.
Practice, Practice, Practice
As we stated at the top of this page, there are a number of tips and techniques to taking the GMAT that will significantly raise your overall score. This is a test that you can prepare for, despite anything the test-makers state. We strongly encourage you to use actual questions from previous exams as you practice, as we have noticed a material difference in the nature and quality of test questions prepared by ETS versus those written by GMAT prep companies. We also strongly encourage you to practice taking the exam in its computer-adaptive format.
Finally, we encourage you to spend most of your preparation time studying and practicing questions in your weakest subject area. While we believe every test taker benefits by reviewing each GMAT exam section, focusing on your weakest areas will make the most efficient use of your test-prep time.
Don't Wait Too Long to Take the GMAT
Don't count on taking the GMAT at the last minute. Should you need to retake the exam, you will need time both to register for the test again and to have the new scores submitted to schools in time for the application deadlines. Scheduling the GMAT well into the admissions season is also bound to cause most test takers undue stress. With proper planning and insight, you can spare yourself these negative energies and instead focus on maximizing your GMAT score.

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2007-05-10T02:24:00.000-07:00

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