Need Help With Functions

I am a college student studying c programming and i need help with using functions because when i create a program i insert all the code into the main function which is very difficult to work with...

I wondering if there was anyone who could help me understand the basics of using functions...

Thank You.

One of the first functions we used is here.

Take a look how we take the code from main and put it in the function.

If main is a bit difficult to understand, replace main with this

Code:

int main(void)
{
        int i = 5;
        int result;
        result = isPrime(i);
        if(result == 1)
        {
              printf("It is prime\n");
         }
         else
         {
              printf("It is not\n");
          }

        return 0;
}

Originally Posted by Hackstorix

I wondering if there was anyone who could help me understand the basics of using functions...

A function should be anythign that represents a logical unit.

E.g. the area of a circle, or other geometrical shape. The maximum, minimum, or average in a list. Loading a data base of employees from disk. Paying the employees. Saving the updated data with the new pay information back to disk.

There are some tricks. Don't be afraid to softcode a fucntion parameter, then hardcode the argument. Say you input a line consisting of a list of numbers, separated by commas. You can count the numbers by counting the commas.
The function

Code:

int strcount(char *str, char ch)
{
   int answer = 0;
   while(*str)
   {
     if(*str =ch)
       answer++;
     str++;
   }
   return answer;
}

will do this for you. However the comma will be hardcoded, higher up.

Code:

Nnumbers = strcount(line, ',') + 1;

The second trick is to use pointers a lot. Virtually all of you C functions will pass information to and from caller, using pointers,usually pointers to structures or arrays of structures.

Also use malloc() a lot. Mostly there won't be a natural limit to the
amount of data you are operating on. By using malloc(), you allow the program to grow, until the machine runs out of memory.

thanks for your help
std10093

Malcolm McLean