In this program the compiler will not know that the function display() exists. So, the compiler will generate "Type mismatch in redeclaration of function display()".

To over come this error, we have to add function prototype of function display().
Another way to overcome this error is to define the function display() before the int main(); function.

#include<stdio.h>
void display();

int main()
{
    display();
    return 0;
}
void display()
{
    printf("Pak-mcqs.net");
}

Output: pak-mcqs.net

Note: This problem will not occur in modern compilers (this problem occurs in TurboC but not in GCC).