A C program basically has the following form:
Statements & Expressions
The Below program is written in the C programming language. Open a text file NewFile.c
using vi editor and put the following lines inside that file.
/* My first program */
printf("NewFile., World! \n");
Preprocessor Commands: These commands tells the compiler to do preprocessing
before doing actual compilation. Like #include <stdio.h> is a
preprocessor command which tells a C compiler to include stdio.h file before going
to actual compilation. You will learn more about C Preprocessors in C Preprocessors session.
Functions: are main building blocks of any C Program. Every C Program will
have one or more functions and there is one mandatory function which is called main()
function. This function is prefixed with keyword int which means this
function returns an integer value when it exits. This integer value is retured using
The C Programming language provides a set of built-in functions. In the above example
printf() is a C built-in function which is used to print anything on the
screen. Check Builtin function section for
You will learn how to write your own functions and use them in Using Function session.
Variables: are used to hold numbers, strings and complex data for
manipulation. You will learn in detail about variables in C Variable Types.
Statements & Expressions : Expressions combine variables and constants to
create new values. Statements are expressions, assignments, function calls, or
control flow statements which make up C programs.
Comments: are used to give additional useful information inside a C Program.
All the comments will be put inside /*...*/ as given in the example above. A comment
can span through multiple lines.
C is a case sensitive programming language. It means in C printf and
Printf will have different meanings.
C has a free-form line structure. End of each C statement must be marked with
Multiple statements can be one the same line.
White Spaces (ie tab space and space bar ) are ignored.
Statements can continue over multiple lines.
To compile a C program you would have to Compiler name and program files name.
Assuming your compiler's name is cc and program file name is NewFile.c, give
following command at Unix prompt.
This will produce a binary file called a.out and an object file NewFile.o in
your current directory. Here a.out is your first program which you will run at Unix
prompt like any other system program. If you don't like the name a.out then
you can produce a binary file with your own name by using -o option while compiling
C program. See an example below
$cc -o NewFile. NewFile.c
Now you will get a binary with name NewFile.. Execute this program at Unix
prompt but before executing / running this program make sure that it has execute
permission set. If you don't know what is execute permission then just follow these
$chmod 755 NewFile.
This will produce following result
Congratulations!! you have written your first program in "C". Now believe me its not
difficult to learn "C".
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