- A function is a block of code that performs a specific task.
- It has a unique name and it is reusable i.e. it can be called from any part of a program.
- Parameter or argument passing to function is optional.
- It is optional to return a value to the calling program. Function which is not returning any value from function, their return type is void.
- While using function, three things are important.
Function Declaration
- Like variables, all the functions must be declared before they are used.
- The function declaration is also known as function prototype or function signature. It consists of four parts,
- Function type (return type)
- Function name
- Parameter list
- Terminating semicolon
Syntax:
FunctionName (Argument1, Argument2,...);
Example:
int sum(int , int);
In this example, function return type is int, name of function is sum, 2 parameters are passed to function and both are integer.
Function Definition
- Function Definition is also called function implementation.
- It has mainly two parts.
- Function header: It is the same as function declaration but with argument name.
- Function body: It is actual logic or coding of the function.
Function Call
- Function is invoked from main function or other function that is known as function call.
- Function can be called by simply using a function name followed by a list of actual argument enclosed in parentheses.
Syntax or general structure of a Function
FunctionName (Argument1, Argument2,...) {
Statement1;
Statement2;
Statement3;
}
An example of function
#include <stdio.h>
int sum(int, int);
void main() {
int a, b, ans;
scanf(“%d%d”, &a, &b);
ans = sum(a, b);
printf(“Answer = %d”, ans);
}
int sum (int x, int y) {
int result;
result = x + y;
return (result);
}