C Language Introduction
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C is a general-purpose, high-level language that was originally developed by
Dennis M. Ritchie to develop the UNIX operating system at Bell Labs. C was
originally first implemented on the DEC PDP-11 computer in 1972.
In 1978, Brian Kernighan and Dennis Ritchie produced the first publicly
available description of C, now known as the K&R standard.
The UNIX operating system, the C compiler, and essentially all UNIX application
programs have been written in C. C has now become a widely used professional
language for various reasons −
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Easy to learn
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Structured language
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It produces efficient programs
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It can handle low-level activities
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It can be compiled on a variety of computer platforms
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Facts about C
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C was invented to write an operating system called UNIX.
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C is a successor of B language which was introduced around the early 1970s.
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The language was formalized in 1988 by the American National Standard Institute
(ANSI).
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The UNIX OS was totally written in C.
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Today C is the most widely used and popular System Programming Language.
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Most of the state-of-the-art software have been implemented using C.
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Today's most popular Linux OS and RDBMS MySQL have been written in C
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Why use C?
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C was initially used for system development work, particularly the programs that
make-up the operating system. C was adopted as a system development language
because it produces code that runs nearly as fast as the code written in
assembly language. Some examples of the use of C might be −
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Operating Systems
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Language Compilers
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Assemblers
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Text Editors
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Print Spoolers
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Network Drivers
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Modern Programs
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Databases
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Language Interpreters
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Utilities
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Local Environment Setup
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If you want to set up your environment for C programming language, you need the
following two software tools available on your computer, (a) Text Editor and (b)
The C Compiler. |
Text Editor
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This will be used to type your program. Examples of few a editors include
Windows Notepad, OS Edit command, Brief, Epsilon, EMACS, and vim or vi.
The name and version of text editors can vary on different operating systems.
For example, Notepad will be used on Windows, and vim or vi can be used on
windows as well as on Linux or UNIX.
The files you create with your editor are called the source files and they
contain the program source codes. The source files for C programs are typically
named with the extension ".c".
Before starting your programming, make sure you have one text editor in place
and you have enough experience to write a computer program, save it in a file,
compile it and finally execute it.
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The C Compiler
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The source code written in source file is the human readable source for your
program. It needs to be "compiled", into machine language so that your CPU can
actually execute the program as per the instructions given.
The compiler compiles the source codes into final executable programs. The most
frequently used and free available compiler is the GNU C/C++ compiler, otherwise
you can have compilers either from HP or Solaris if you have the respective
operating systems.
The following section explains how to install GNU C/C++ compiler on various OS.
We keep mentioning C/C++ together because GNU gcc compiler works for both C and
C++ programming languages.
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//Hello World Program
#include <stdio.h>
#include<conio.h>
void main()
{
clrscr();
printf("Hello!");
getch();
} |
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To compile & Run this program in turboc use Short Cut < ctrl+f9> |
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Before we study the basic building blocks of the C programming language, let us
look at a bare minimum C program structure so that we can take it as a reference
in the upcoming chapters.
Hello World Example
A C program basically consists of the following parts −
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Preprocessor Commands
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Functions
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Variables
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Statements & Expressions
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Comments
Let us look at a simple code that would print the words "Hello World"
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#include <stdio.h>
int main() {
/* my first program in C */
printf("Hello, World! \n");
return 0;
}
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Let us take a look at the various parts of the above program −
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The first line of the program #include <stdio.h> is a preprocessor command, which tells
a C compiler to include stdio.h file before going to actual compilation.
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The next line int main() is the main function where the program
execution begins.
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The next line /*...*/ will be ignored by the compiler and it has been put to add
additional comments in the program. So such lines are called comments in the
program.
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The next line printf(...) is another function available in C
which causes the message "Hello, World!" to be displayed on the screen.
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The next line return 0; terminates the main() function and
returns the value 0.
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