Understanding Return Types in C Functions: Usage and Examples

Return Statement with respect to parameter or arguments in c, there may be four type of condition with respect to arguments, they are below-

1. Take Nothing Return Nothing
2. Take Nothing Return Something
3. Take Something Return Nothing
4. Take Something Return Something

Take Nothind Return Nothing

Program

#include<stdio.h> 
void main( )
{
	
    sum() ;
	
}
 
void sum(){
    int a, b, total ; 
	printf("\nEnter any two numbers ") ;
	scanf("%d %d", &a, &b) ; 
	total = a + b ;
	printf("\n Sum = %d \n", total ) ;
}

Output

Enter any two numbers 2  3

 Sum = 5
Press any key to continue . . .

Take Nothind Return Something

Program

#include<stdio.h> 
void main( )
{
    int return_sum;
	
    return_sum=sum() ;
    
    printf("\n Sum = %d \n", return_sum ) ;
	
}
 
int sum(){
	int a, b, total ; 
	printf("\nEnter any two numbers " ) ;
	scanf("%d %d", &a, &b) ; 
	total = a + b ;
	return total;
	
}

Output

Enter any two numbers 2  3

 Sum = 5
Press any key to continue . . .

Take Something Return Nothing

Program

#include<stdio.h> 
void main( )
{
	int a, b, total ; 
	printf("\nEnter any two numbers " ) ;
	scanf("%d %d", &a, &b) ;
    sum(a, b) ;
	
}
 
void sum(x, y){
	int d ;
	d = x + y ;
	printf("\n Sum = %d \n", d ) ;
}

Output

Enter any two numbers 2  3

 Sum = 5
Press any key to continue . . .

Take Something Return Something

Program

#include<stdio.h> 
void main( )
{
	int a, b, total ; 
	printf("\nEnter any two numbers " ) ;
	scanf("%d %d", &a, &b) ;
	total = sum(a, b) ;
	printf("\n Sum = %d \n", total ) ;
}
 
int sum(x, y){
	int d ;
	d = x + y ;
	return d;
}

Output

Enter any two numbers 2  3

 Sum = 5
Press any key to continue . . .

Scope Rule of Functions

Look at the following program

Program

#include<stdio.h> 
void main()
{
	int i = 20 ;
	message(i) ;
}

void message(int j)
{
	int k = 35 ;
	printf("\n%d", j) ;
	printf("\n%d\n", k) ;
}

Program

20
35
Press any key to continue . . .

In this program is it necessary to pass the value of the variable i to the function message( )? Will it not become automatically available to the function message( )? No. Because by default the scope of a variable is local to the function in which it is defined. The presence of i is known only to the function main( ) and not to any other function. Similarly, the variable k is local to the function message( ) and hence it is not available to main( ). That is why to make the value of i available to message( ) we have to explicitly pass it to message( ). Likewise, if we want k to be available to main( ) we will have to return it to main( ) using the return statement. In general we can say that the scope of a variable is local to the function in which it is defined.