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How communication among functions is established in C language?
Functions communicate among themselves with the help of arguments and return value.
Farm of ‘C’ function is as follows −
return-datatype function name (argument list){
local variable declarations;
executable statements(s);
return (expression);
}For example, void mul (int x, int y)
{
int p;
p=x*y;
printf("product = %d”,p);
}Return values and their types
- A function may or may not send back a value to the calling function.
- It will be done by using the return statement
- The return types are void, int, float, char and double.
- If a function is not returning any value, then its return type is ‘void’.
Function name
A function must follow the rules just like the variables name in ‘C’.
A function name must not a predefined function names.
Argument list
In this list the variable names separated by commas.
The argument variables receive values from the calling function, which provides a means for data communication from the calling function to the called function.
Calling a function
A function can be called by using the function name in a statement.
Function definition
Whenever, a function call, the control is transferred to the function definition.
All the statements, in called function are called as function definition.
Function header
- The first line in the function definition.
Actual parameter
- All the variables inside the function call.
Formal parameters
All the variables inside the function header are called formal parameters.
Example
Following is the C program for communication among the functions −
#include<stdio.h>
#include<conio.h>
main ( ){
int mul (int, int); // function prototype
int a,b,c;
clrscr( );
printf ("enter 2 numbers”);
scanf("%d %d”, &a, &b);
c = mul (a,b); // function call
printf("product =%d”,c); Actual parameters
getch ( );
}
int mul (int a, int b){ // Formal parameters
//function header
int c;
c = a *b; //Function definition
return c;
}Output
When the above program is executed, it produces the following result −
Enter 2 numbers: 10 20 Product = 200
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