Code:
/*

CS50 Problem Set 2

This program asks for the user to specify how much change is due and then returns the smallest number of coins that could be combined to give the correct change.  Implements the "greedy algorithm."

Project Started: 5/7/2009 10:20pm
V1 Completed:
Last Modified:

*/

#include <stdio.h>

int
main(int argc, char *argv[]){

        int countCoints();

        float change;
        int coinsDue;

        printf("How much change is due?\n");
        scanf("%f", &change);

        coinsDue = countCoins(change);

        printf("%d", coinsDue);


}

int
countCoins(float c){

        int input = (float) c;

        int numCoins = 0; //numCoins stores the current number of coins needed to give correct change

        float penniesLeft = (int) (input*100); //initializes to total change due in pennies to eliminate loss in floating point precision

        while(penniesLeft > 0){

                if(penniesLeft >= 25){ //if quarters can be given

                        int numQuarters;

                        numQuarters = (int)(penniesLeft/25); //finds out how many quarters can be given
                        penniesLeft -= (numQuarters*25); //subtracts change given in quarters from change sti$
                        numCoins += numQuarters;

                }

                if(penniesLeft >= 10){ //if dimes can be given

                        int numDimes;

                        numDimes = (int)(penniesLeft/10); //finds out how many quarters can be given
                        penniesLeft -= (numQuarters*10); //subtracts change given in dimes from change still $
                        numCoins += numDimes;

                }

        }

        return numCoins;
}
(line 34) error: conflicting types for ‘countCoins’
(line 34) note: an argument type that has a default promotion can’t match an empty parameter name list declaration
(line 26)error: previous implicit declaration of ‘countCoins’ was here
In function ‘countCoins’:
(line 59) error: ‘numQuarters’ undeclared (first use in this function)
(line 59) error: (Each undeclared identifier is reported only once for each function it appears in.)

hmmm I can't seem to find an instance of declaring countCoins() anything other than an integer...

I don't know why the error on line 26 is an error;

And numQuarters IS declared in the function!

I'm new to C, and it's been a while since I've programmed anything other than PHP, so I'm probably missing something basic here... I've looked at tutorials for calling functions but none of them seem to suggest a solution to my errors.