The C is a general-purpose, procedural,
imperative computer programming language developed in 1972 by Dennis M. Ritchie
at the Bell Telephone Laboratories to develop the UNIX operating system.
The C is the most widely used computer
language, it keeps fluctuating at number one scale of popularity along with
Java programming language, which is also equally popular and most widely used
among modern software programmers.
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 applications programs have been written in C. The C has now become a
widely used professional language for various reasons.
·
Easy to learn
·
Structured language
·
It produces efficient programs.
·
It can handle low-level activities.
·
It can be compiled on a variety of
computer platforms.
Facts about C
·
C was invented to write an operating
system called UNIX.
·
C is a successor of B language which
was introduced around 1970
·
The language was formalized in 1988
by the American National Standard Institute (ANSI).
·
The UNIX OS was totally written in C
by 1973.
·
Today C is the most widely used and
popular System Programming Language.
·
Most of the state-of-the-art
softwares have been implemented using C.
·
Today's most popular Linux OS and
RBDMS MySQL have been written in C.
Why to use C?
C was initially used for system development work, in
particular 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 code written in assembly language. Some examples of the use of C might be:
·
Operating Systems
·
Language Compilers
·
Assemblers
·
Text Editors
·
Print Spoolers
·
Network Drivers
·
Modern Programs
·
Databases
·
Language Interpreters
·
Utilities
C Programs
A C program can vary from 3 lines to millions of lines and
it should be written into one or more text files with extension ".c";
for example, hello.c.
Before we study basic building blocks of the C programming
language, let us look a bare minimum C program structure so that we can take it
as a reference in upcoming chapters.
C Hello World Example
A C program basically consists of the following parts:
·
Preprocessor Commands
·
Functions
·
Variables
·
Statements & Expressions
·
Comments
Let us look at a simple code that would print the words
"Hello World":
#include <stdio.h>
int main()
{
/* my first program in
C */
printf("Hello,
World! \n");
return 0;
}
Let us look various parts of the above program:
1.
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.
2.
The next line int main() is the main function where program
execution begins.
3.
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.
4.
The next line printf(...) is another function available in C
which causes the message "Hello, World!" to be displayed on the
screen.
5.
The next line return 0; terminates main()function and
returns the value 0.
Compile & Execute C Program:
Lets look at how to save the source code in a file, and how
to compile and run it. Following are the simple steps:
1.
Open a text editor and add the
above-mentioned code.
2.
Save the file as hello.c
3.
Open a command prompt and go to the
directory where you saved the file.
4.
Type gcc hello.c and
press enter to compile your code.
5.
If there are no errors in your code
the command prompt will take you to the next line and would generate a.out executable file.
6.
Now, type a.out to execute your program.
7.
You will be able to see "Hello World" printed on the screen
$ gcc hello.c
$ ./a.out
Hello, World!
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