gistfile1_withcomments.c

#include <cs50.h>
#include <stdio.h>
#include <math.h>
 
int main(void)
{
    /* Note that all of these variables are initialized with undetermined values. This will be important later. */
    int quarters, dimes, nickles, pennies;
    float quarters_filter, dimes_filter, nickles_filter;
    
    printf("You need change? How much?");
    float dollar_amount = GetFloat();
    
    /* I'm curious if you know why this works. */
    quarters = dollar_amount / 0.25;

    /*
        This loop will execute at least once, regardless of the value of dollar_amount.
        This is the point of do/while. You want to use while here so that the loop is only
        entered if dollar_amount has any quarters to begin with.
    */
    do
    {
        /* I have no idea what quarters_filter is supposed to do */
        quarters_filter = dollar_amount - 0.25;
    }
    while (dollar_amount > 0.25 );
    
    float quarter_reciprocal = quarters_filter - quarters;
    
    dimes = quarter_reciprocal / 0.10;
    
    do 
    {
        dimes_filter = quarter_reciprocal - 0.10;
    }
    
    while (quarter_reciprocal > 0.10);
    
    float dime_reciprocal = dimes_filter - dimes;
    
    nickles = dime_reciprocal / 0.05;
    
    do
    {
        nickles_filter = dime_reciprocal - 0.05; 
    }
    
    while (dime_reciprocal > 0.05);
    
    float nickle_reciprocal = nickles_filter - nickles;
    
    pennies = nickle_reciprocal / 0.01;
    
    printf("%d\n", quarters);
    printf("%d\n", dimes); 
    printf("%d\n", nickles);
    printf("%d\n", pennies);
    
    return 0; 
 
} 

/* As I would write it following your approach */
void main()
{
    int quarters, dimes, nickles, pennies;
    
    printf("You need change? How much?");
    float dollar_amount = GetFloat();
    
    quarters = dollar_amount / 0.25;

    while (dollar_amount >= 0.25)
    {
        dollar_amount -= 0.25;
    }
    
    dimes = dollar_amount / 0.10;    

    while (dollar_amount >= 0.10)
    {
        dollar_amount -= 0.10;
    }
    
    nickles = dollar_amount / 0.05;
    
    while (dollar_amount >= 0.05)
    {
        dollar_amount -= 0.05;
    }
        
    pennies = dollar_amount / 0.01;
    
    printf("%d\n", quarters);
    printf("%d\n", dimes); 
    printf("%d\n", nickles);
    printf("%d\n", pennies);
    
    return 0; 
}

/* As I would write it following a different approach */
void main()
{
    int quarters, dimes, nickles, pennies;
    
    printf("You need change? How much?");
    float dollar_amount = GetFloat();
    
    quarters = dollar_amount / 0.25;
    dollar_amount -= quarters * 0.25;
    
    dimes = dollar_amount / 0.10;
    dollar_amount -= dimes * 0.05;
    
    nickles = dollar_amount / 0.05;
    dollar_amount -= nickles * 0.05;
        
    pennies = dollar_amount / 0.01;
    
    printf("%d\n", quarters);
    printf("%d\n", dimes); 
    printf("%d\n", nickles);
    printf("%d\n", pennies);
    
    return 0; 
}