C Functions

For creating an function we first need to declare the function (Function Prototype) and then implement the function (Function Definition)
Function Prototype is option but is the recommended way of declaring functions

#include <stdio.h>
 
// Function Prototype
void printName(char[]);
 
int main()
{
    printName("David");
}
 
// Function Defination
void printName(char name[])
{
    printf("Hello my name is %s\n", name);
}

NOTE

• Function can only return a single parameter
• When writing large programs Function Prototypes are written in Header files

We can return multiple values by:

• Declaring a struct to encapsulate the parameters to be returned
• Using pointers passed as inputs to function to store the results

#include <stdio.h>
 
void sum(int, int, int *);
 
int main(int argc, char const *argv[])
{
    int result;
    sum(5, 15, &result);
    printf("%d\n", result);
}
 
void sum(int num1, int num2, int *result)
{
    *result = num1 + num2;
}

Functions can be represented as pointers as and can be passed to functions

#include <stdio.h>
 
int sum(int, int);
int prod(int, int);
void super_func(int (*)(int, int), int, int);
 
int main(int argc, char const *argv[])
{
	// Passing address of function as function
    super_func(&sum, 3, 4);
 
	// Assigning address of function to pointer
    int (*func)(int, int) = &prod; 
    int result = (*func)(2, 6);
    printf("%d\n", result);
 
    return 0;
}
 
int sum(int x, int y)
{
    return x + y;
}
 
int prod(int x, int y)
{
    return x * y;
}
 
void super_func(int (*operation)(int, int), int x, int y)
{
    printf("%d\n", operation(x, y));
}