Types of functions:

• Standard library functions (inbuilt functions) : printf(), sqrt()

  

• User-defined functions

  #include <stdio.h>
  #include <math.h>
  
  int functionName(a,b)
  {
      ... .. ...
      ... .. ...
  }
  
  int main()
  {
      ... .. ...
      ... .. ...
  
      somme = functionName(a,b);
      
      ... .. ...
      ... .. ...
  }
  

  • No arguments passed and no return value
  • No arguments passed but a return value
  • Argument passed but no return value
  • Argument passed and a return value

Example (User-defined function)

#include <stdio.h>

int sumIntegers(int a, int b);         // function prototype (declaration)

int main()
{
    int int1,int2,result;
    printf("Enters two numbers: ");
    scanf("%d %d",&int1,&int2);

    result= sumIntegers(int1, int2);        // function call

    printf("result= %d",result);

    return 0;
}

int sumIntegers(int a, int b)         // function definition   
{
    int c;
    c= a + b;

    return c;                  // return statement
}

// Passing arrays to functions
float calculateSum(int X[]) {
    ... ..
}

// Passing two-dimensional arrays
void displayNumbers(int X[2][2])
{
    ... ..
}