Displaying numbers to two decimal places using printf

Hey

I am currently in uni and I have just started to learn basic C. For a project, I have to make a simple application that can convert GBP into euros (roughly). The problem I have is displaying the input and the output as a decimal number.

Here is my code:

Code:

---

/*        Currency conversion app
                  Kieran Symes      */

#include <stdio.h>

void welcome(void); //displays welcome message and app info
void convert(void); //converts users input to $


int main()
{

        welcome();
  convert();

        return 0;
}

//this bit welcomes the user and shows some info
void welcome(void)
{
        printf ("Currency Converter\nBy Kieran Symes\n24/10/2006\n\n");

}

void convert(void)
{

float input;
float output;

        printf("Please enter an amount you wish to convert\n");
  scanf("%f", &input);

  output = input * 1.5;

  printf("£%f is equal to %f euros.", input, output);

}

---

The output for this, say if I enter 21 is

£21.000000 is equal to 31.500000 euros. but I want these figures to be displayed in currency format.

Any help and comments will be appreciated. Thanks

I think %g does trailing zero suppression.

Though if you also want say 21.00, then you'll need another approach.

will

Code:

---

printf("£%.2f is equal to %.2f euros.", input, output);

---

work??

by currency format , U mean , U need two digits after the decimal right? I think sangken is right..

that has worked perfectly

thanks for your help :D

so could you help me validate the data to ensure it is a number?

i guess an if statement would be best although I don't know what to analyze data obtained from scanf.

I guess it would be an if statement like this...

if the data is numeric
go to the convert fucntion
else
print message warning
loop back to input function

I have to include a few functions see

thanks again for your help

U can consider using
" isdigit() " to do that..
Check the man pages

You COULD of course go into checking values and all such things, but funny thing:
scanf(); only accepts input that fits into the format string!

Code:

---

scanf("%.2f", FloatNum);

---

Only accepts a number that fits into a float of the format #.?? (ie 12.64 or 53.00)
checking to see if FloatNum is indeed a float and getting an error from that would be a marvellous discovery and do please document it well ;-).

i am trying the following code within the convert function

Code:

---

void convert(void)
{
float input;
float output;
        printf("Please enter an amount you wish to convert\n");
  scanf("%f", &input);
        if(isdigit(input))  //prblem code
  {
  output = input * 1.49;
  printf("£%.2f is equal to %.2f euros.", input, output);
  }
  else
  {
  printf("There was an error with your entry.  Please try again\n")
  convert();
  }


}

---

i have had a look into isdigit() and it looks like what I need although I am unable to get it to work.

does it look like I have used it right?

>does it look like I have used it right?
No, isdigit takes an int/char. You're passing it a float (float input).

If you want to validate with isdigit, first use fgets to read into a string, then use strtod to convert to a float or double after checking for valid input. Or you could do the validation with strtod.

i thought it may have been because it's a float.

how would I use strtod? could you give me some sample code?

thanks

>could you give me some sample code?

Code:

---

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

int main(void)
{
        char line[80];
        double amount;
        char *endptr;
        int valid = 0;

        do {
                printf("Please enter an amount you wish to convert: ");
                fgets(line, 80, stdin);
                amount = strtod(line, &endptr);
                if (endptr == line)
                {
                        printf("Invalid input.\n");
                        valid = 0;
                }
                else
                {
                        valid = 1;
                }
        } while (!valid);

        printf("Amount: %.2f\n", amount);

---

Quote:

---

Originally Posted by Asmyldof

You COULD of course go into checking values and all such things, but funny thing:
scanf(); only accepts input that fits into the format string!

Code:

---

scanf("%.2f", FloatNum);

---

Only accepts a number that fits into a float of the format #.?? (ie 12.64 or 53.00)
checking to see if FloatNum is indeed a float and getting an error from that would be a marvellous discovery and do please document it well ;-).

---

The highlighted material is incorrect.

You can also use sscanf in place of strtod if you prefer:

Code:

---

      if (sscanf(line, "%f", &amount) != 1)
      {
        printf("Invalid input.\n");
        valid = 0;
      }

---

Then you don't need endptr.

Maybe a bit ahead of the game, but possibly something to look at:
http://www.daniweb.com/code/snippet258.html

hey, i got it to work using bits from the code by swoopy

thanks for all your help (and sorry I didn't reply till now)

:D