Thread: Need help with C program

First, you break it down into steps. Then you convert that into code. Logicly, in your mind, break down how you give change to someone. You do know how to give change, right? Start with the largest amount, which is smaller or equal to the amount of change, and subtract that. Keep subtracting it until the remainder is smaller than that money size. Then move down to the next smaller size. Repeat until you have given all of the change you need.

Now it's your turn.

Quzah.

Ah, that's a good start.

Converting ideas to the C language is not difficult. It is almost like taking your ideas and talking them through to the compiler. For example.

1) I enter price of item
» This tells us we need to either write a function or use a standard function to get input from the user. The best way to find out how to do this is some searching. To make this easier, lets just say we happened upon a site: cplusplus.com reference. This is a good site that explains most, if not all, of the standard library functions within the C language. We spot out stdio.h, string.h, and stdlib.h first. We know string.h has to do with strings, and stdlib with the standard library, while stdio is for I/O or Input and Output. Exactly what we need!

We scroll down for a bit and happen upon scanf(). What does this function do? It reads formatted data from stdin. Also what we need. stdin is the input stream, while stdout is the output stream.

Of course you can learn more about scanf() by clicking here.

2) I enter amount paid
» We do the same above but again with another variable. One for amount, and one for price.

3) Subtract amount paid minus the price
» Mathematics in C isn't any harder than paper. Just do: difference = paid - price. Quite simple in terms.

4) print this number as change due
» We we know about scanf() that takes input, but what about a function that prints output. If we go back to the cplusplus.com reference page we can look 8 functions up from where you found scanf(). What do we see? printf(). What does printf() do? It prints formatted data to stdout. Exactly. It works almost identical to scanf() though we print out variables that already exist. Here is more info about printf().

I hope this helps. If you have further questions, please feel free to ask.

Note: Each of the links of printf() and scanf() have full examples at the bottom of each page.

I hope this helps you get started. The ideas you have in mind for your project will take more than the first 4 steps, but its a start!


- Stack Overflow

1) Loop through your bills starting at the largest
2) While the value of that bill plus the amount of change you've already handed out is less than the total change due, give another bill.

> do you mind giving me a quick example
» Not at all. Just for examples sake lets look at the following.

The while loop
The while loop has a syntax of the following:

Code:

while (expression) {
	statement
}

This should make sense. As long as the expression is true, the statement executes.

So lets take for instance 43 dollars. If we wanted to sucessfully find how many tens are in forty-three dollars all we would have to do is run a while loop in statement like the following:

Code:

As long as money is greater than 10
Subtract 10
Increment tens counter

If this makes sense, so should this:

Code:

int tens = 0, money = 43;

while (money > 10) {
	money -= 10;
	tens++;
}

That is just an example of how it could work. Everytime the while loop executes, money is subtracted by 10 and our integer called tens is incremented. The answer should be '4 tens'. After a while the loop does run out of 10's to subtract. Though of course we haven't printed any output so we would never know.

If you have further questions, please feel free to ask.


- Stack Overflow

Alright,

You haven't gone off my page yet

Lets go back to the cplusplus reference page. We are familar with scanf() and printf(), though there is a new one: fscanf()

Why is it called fscanf()? Because it reads formatted data from a stream. File Scan Format - fscanf() [or that is my analogy]

How does fscanf() work? Well, that link should show you everything you need to know.

fscanf() does need an open stream of a file. Though we haven't opened a file yet. How do we? We use fopen() - File Open [simple, eh?]

fopen() works like a charm. You open a file with your filename and you can read it into memory, or better yet just open it and start scanning away with fscanf(). If you look near the bottom of fscanf()'s page you will see fopen() and fclose() being used.

This works like the following:

Code:

Open the file
Scan inside the file
Close the file

Hope this helps,
- Stack Overflow

Code:

#include <math.h>
#include <stdio.h>
#include <stdlib.h>

#define STAGE_LEFT EXIT_FAILURE
#define ENCORE EXIT_SUCCESS
#define TOO_SHORT NULL
#define toilet stdout
#define BLING 1
#define EMPTY_WALLET 0

double jinglie[] = {
  100.00, 50.00, 20.00, 10.00, 5.00, 1.00, .50, .25, .10, .05, .01
};

int main ( void )
{
  char thingie[BUFSIZ];
  double all_zat, da_dough, leftovas;

  printf ( "Price: " );
  fflush ( toilet );
  if ( fgets ( thingie, sizeof thingie, stdin ) == TOO_SHORT
    || sscanf ( thingie, "%lf", &all_zat ) != BLING )
  {
    exit ( STAGE_LEFT );
  }

  printf ( "Amount: " );
  fflush ( toilet );
  if ( fgets ( thingie, sizeof thingie, stdin ) == TOO_SHORT
    || sscanf ( thingie, "%lf", &da_dough ) != BLING )
  {
    exit ( STAGE_LEFT );
  }

  leftovas = da_dough - all_zat;

  printf ( "Change Due:\n" );
  if ( leftovas >= EMPTY_WALLET ) {
    int stuff = 0;

    while ( stuff < sizeof jinglie / sizeof *jinglie ) {
      if ( leftovas >= jinglie[stuff] ) {
        printf ( "%.2f\n", jinglie[stuff] );
        leftovas -= jinglie[stuff];
      }
      else
        ++stuff;
    }
  }
  else
    printf ( "You still owe %.2f\n", fabs ( leftovas ) );

  return ENCORE;
}

Oh, I kill me.

Ah Prelude,

All my efforts for nothing! Just kidding.

I like the code personally, though it may confuse a beginner programmer.

All in all, gain help and gain trust; as they say it.


- Stack Overflow

Originally Posted by Prelude

Code:

#include <math.h>
#include <stdio.h>
#include <stdlib.h>

#define STAGE_LEFT EXIT_FAILURE
#define ENCORE EXIT_SUCCESS
#define TOO_SHORT NULL
#define toilet stdout
#define BLING 1
#define EMPTY_WALLET 0

double jinglie[] = {
  100.00, 50.00, 20.00, 10.00, 5.00, 1.00, .50, .25, .10, .05, .01
};

int main ( void )
{
  char thingie[BUFSIZ];
  double all_zat, da_dough, leftovas;

  printf ( "Price: " );
  fflush ( toilet );
  if ( fgets ( thingie, sizeof thingie, stdin ) == TOO_SHORT
    || sscanf ( thingie, "%lf", &all_zat ) != BLING )
  {
    exit ( STAGE_LEFT );
  }

  printf ( "Amount: " );
  fflush ( toilet );
  if ( fgets ( thingie, sizeof thingie, stdin ) == TOO_SHORT
    || sscanf ( thingie, "%lf", &da_dough ) != BLING )
  {
    exit ( STAGE_LEFT );
  }

  leftovas = da_dough - all_zat;

  printf ( "Change Due:\n" );
  if ( leftovas >= EMPTY_WALLET ) {
    int stuff = 0;

    while ( stuff < sizeof jinglie / sizeof *jinglie ) {
      if ( leftovas >= jinglie[stuff] ) {
        printf ( "%.2f\n", jinglie[stuff] );
        leftovas -= jinglie[stuff];
      }
      else
        ++stuff;
    }
  }
  else
    printf ( "You still owe %.2f\n", fabs ( leftovas ) );

  return ENCORE;
}

Oh, I kill me.

really girl. you just all dat and a big bag 'O chips wit da Dips!!! LOL. seriously, your a goddess. I can't wait till I'm where you are. Kudos.
flawless!

Yes, that code is fine.

fscanf(transactions, "%f\n", &cost);
> Gets the cost from the file

printf ("The cost is %g\n", cost);
> Prints the cost that we got from file

fscanf(transactions, "%f\n", &payment);
> Gets the payment from file

printf("The customer's payment was %g\n", payment);
> Prints the payment we got from file

change = cost - payment;
> Gets the difference between the two

printf("The change due is %g\n", change);
> Prints that difference we just calculated.