Introduction to C Programming

Features of C Programming

• C is a small language having lesser number of keywords than Java or pascal.
• C is a native language of Unix, Linux. Not only that many of the windows packages, database programs, graphics libraries are written in C program
• C is portable – it provides standard set of libraries that work on the same way with all machines
• C is modular, as it supports functions to divide the program in to sub program
• C is efficient on most machines, because certain constructs are machine dependant.

Structure of a C program

• Comments
• the comments are usually ignored by the compiler
• so this part informs about the author of the program
• what is the usefulness of this program
• updation or creation of the program
• Example: //  - Single line comment
• /* ----- multi line comments    ….*/
• Preprocessor Directives
• before the compiler runs, the preprocessing takes place.
• the preprocessors are prefix with a symbol #
• Examples: #include, #define, #ifdef, #pragma, etc.
• Function prototypes
• This is to inform the compiler that the following functions are defined in this program.
• it specifies the name of the function, arguments or parameters and return type and it ends with a semicolon
• Ex: int sum(int,int);
• Global Variables
• Global variables which are declared above all the functions
• As the name says, they are available to all the functions of that program
• They are usually stored in the RAM
• Main Function
• main is the function which is main to the entire program
• Every C program should have a main function
• syntax: int main() { }
• Earlier, the main program will return nothing, ie void, but now the compilers are instructing us to provide a return type for the main() function
• User defined functions
• After the main() function, the user defined functions are defined, as per the function prototype declared in the program
• The function can be defined above the main function also, in that case there is not need for function prototype
• Syntax:

int sum(int a, int b)

{

int f;

f=a+b;

return f;

}