How to fix Error: unused variable (Pset 1 - Greedy)

Question

I don't understand why I keep getting an error message regarding the variable "amount." Can anyone identify/explain the problem and how to fix it? The relevant part of my code is below. Thanks in advance.

int main(void) 
{
    int coin_count = 0;

    do 
    {
        printf("How much change is owed (amount must be non-negative): \n"); 
        float amount = get_float(); 
    }
    while(amount < 0);

    int cent_amount = round(amount*100);

   while(cent_amount>0)
   {
       if(cent_amount > 25)
       {
           cent_amount = cent_amount - 25;
           coin_count++;
       }
       else if(cent_amount > 10)
       {
           cent_amount = cent_amount - 10;
           coin_count++;
       }
       else if(cent_amount > 5)
       {
           cent_amount = cent_amount - 5;
           coin_count++;
       }
       else if(cent_amount > 1)
       {
           cent_amount = cent_amount - 1;
           coin_count++;
       }
   }
   printf("Minimum number of coins used: %i\n", coin_count);
}

Answer 1

This is a visibility problem, amount only exists inside the loop, the solution is to declare amount hole of the loop:

float amount;

And then inside the loop:

amount = get_float;