Function is defined above the function main: it is not necessary to prototype the function
#include <stdio.h>
void f1(int *k)
{
*k = *k + 10;
}
main ( ){
int i;
i = 0;
printf (" The value of i before call %d \n", i);
f1 (&i);
printf (" The value of i after call %d \n", i);
}The value of i before call 0
The value of i after call 10
Function is defined after main: prototype the function
#include <stdio.h>
f1(int *k);
main ( ){
int i;
i = 0;
printf (" The value of i before call %d \n", i);
f1 (&i);
printf (" The value of i after call %d \n", i);
}
f1(int *k)
{
*k = *k + 10;
}The value of i before call 0
The value of i after call 10
Function prototype
#include <stdio.h>
int change(int number); /*Function prototype */
int main(void)
{
int number = 10;
int result = 0;
result = change(number);
printf("\nIn main, result = %d\tnumber = %d", result, number);
return 0;
}
int change(int number)
{
number = 2 * number;
printf("\nIn function change, number = %d\n", number);
return number;
}In function change, number = 20
In main, result = 20 number = 10
