#include <stdio.h>
#include <cs50.h>
int main(void)
long creditcardno;
creditcardno = 
while (creditcardno <  0);

The above code accepts positive integers while taking input for credit card no.

The task is now to form a function my_function () that will perform the above task when called in the main function.

All that I can figure out is:

include <stdio.h>
#include <cs50.h>
long my_function (void);

Will the next line include int main (void) or that will not appear at all.

Is it possible that I form a different c file such as test.c that will include function definition only and this file be called in main function in credit.c. Or both possibilities are there. I can have function defined and called in the same file so that everything can be performed from credit.c file.


The structure is simple. Pay attention to placement of curly braces and semicolons, specifically, where they are NOT.

#include statements

// The next line is a function signature to tell the compiler that
// the actual function will follow later.  You either need a signature 
// or the actual function to appear before it is ever used anywhere. 
// note the semicolon here, but not in the similar line at the function. 

int myfunction(<empty or var declarations go here>); 

int main (void)
    // main code goes in here

int myfunction(<empty or var declarations go here>)
    // function code goes in here

That's all there is to it.

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