Functions & Pointers in Programming: Complete Study Guide & Examples for 2026/2027

Functions & Pointers
Functions And Pointers
• Functions are created when the same process or an algorithm to be repeated several times
in various places in the program.
• Function has a self-contained block of code, that executes certain task. A function has a
name, a list of arguments which it takes when called, and the block of code it executes when
called.
• Functions are two types:
1. Built-in / Library function.
Example: printf(), scanf(), getch(), exit(), etc.
2. User defined function.
User-Defined Functions
Functions defined by the users according to their requirements are called user-defined functions.
These functions are used to break down a large program into a small functions.
Advantage of User defined function:
1. Reduce the source code
2. Easy to maintain and modify
3. It can be called anywhere in the program.
Body of user defined function:
return_type f_name (argument1,argument 2)
{
local variables;
statements;
return_type;
}

,The body of user-defined shows that an user-defined functions has following characteristics:
1. Return type
2. Function name
3. Parameter list of arguments
4. Local variables
5. Statements
6. Return value


S.No C function aspects Syntax
1 function definition return_type function_name ( arguments list )
{ Body of function; }
2 function call function_name ( arguments list );
3 function declaration return_type function_name ( argument list );


Note: The function with return value must be the data type, that is return type and return value
must be of same data type.
User defined function has three parts:
1. Declaration part
ret_type f_name (arguments)
2. Calling part
f_name(arguments);

, 3. Definition part
Function Parameters:
Parameters provide the data communication between calling function and called function.
Two types:
◻ Actual parameters:
These are the parameters transferred from the calling function[main function] to the called
function[user defined function].
◻ Formal parameters:
Passing the parameters from the called functions[user defined function] to the calling
functions[main function].
Note:
◻ Actual parameter– This is the argument which is used in function call.
◻ Formal parameter– This is the argument which is used in function definition.
Categories of User defined function/Function Prototypes:
• A function prototype declaration consists of the functions return type, name and
arguments list.
• Always terminated with semicolon.
The following are the function prototypes:
1. Function without return value and without argument.
2. Function without return value and with argument.
3. Function with return value and with argument.
4. Function with return value and without argument.
Note: Function with more than one return value will not have return type and return statement in
the function definition.
Consider the following example to multiply two numbers:
void main( )
{
int x,y,z;
scanf(―%d%d‖, &x,&y);
z=x* y;
printf(―The result is %d‖, z); }