input help

[jjbkeeper]

Hello

First post so hoping you can help.

Having problems with a bit C coding.

Trying to return error when ever inserting a letter or nothing at all.

The code is below, looking for help with the bolded line.

/*******************************************************************************************************************
 Author: Josh Brown
 Date: 28/2/09
 Purpose: Speed Camera
*******************************************************************************************************************/

#include <stdio.h>

int main ()
{
 const int LIMIT = 59, MAX1 = 70, MAX2 = 90; 
 int speed;

 /*Asks User for Speed*/
 printf ("Please enter speed: ");
 scanf ("%d%*c", &speed);

 if (speed <= LIMIT)
  {printf("Not Speeding");}
 else
  if  ( ( speed >= LIMIT ) && ( speed < MAX1 ) )
   {printf("Speeding 1 to 10 Km/h over the limit. Fine is $80");}
  else
   if  ( ( speed >= MAX1 ) && ( speed < MAX2 ) )
    {printf("Speeding 11 to 30 Km/h over the limit. Fine is $150");}
   else
    if (speed >= MAX2)
     {printf("Speeding 30+ Km/h over the limit. Fine is $500");}
    else
      {printf("You did not enter a valid speed");};

	return(0);
}

}

Thanks

Josh

[McClane]

There are two problems that are causing the error message not to be printed:
1) You're not initialising the speed variable and as a result it will contain junk data. When I ran your code I happened to get -1073743700.
2) Your if statement accepts all integer values, positive and negative.

To solve your problem you need to initialise the speed variable to a negative number and you need to check for numbers less than 0. This will mean that if the user enters a negative number (e.g. -10) the speed variable will be set to this number and the < 0 condition in your if statement will be satisfied, thus printing the error message. If the user enters something that isn't a number (e.g. abc) then the speed variable will not be set. However, since it already contains a negative number the error message will be printed.

I have made the changes to your code so you can see what I mean. I have also made some formatting changes which make it easier to read and I've changed your constants to #defines at the top of the file since this is good practice for constant values. This helps with maintainability of your code.

#include <stdio.h>

#define LIMIT 60
#define MAX1 70
#define MAX2 80

int main(void)
{
    int speed = -1;
    
    /* Asks User for Speed */
    printf("Please enter speed: ");
    scanf("&#37;d%*c", &speed);
    
    if(speed < 0)
    {
	printf("You did not enter a valid speed\n");
    }
    else if(speed < LIMIT)
    {
	printf("Not Speeding\n");
    }
    else if(speed < MAX1)
    {
	printf("Speeding 1 to 10 Km/h over the limit. Fine is $80\n");
    }
    else if(speed < MAX2)
    {
	printf("Speeding 11 to 30 Km/h over the limit. Fine is $150\n");
    }
    else
    {
	printf("Speeding 30+ Km/h over the limit. Fine is $500\n");
    }

    return 0;
}

Welcome to Hexus

[jjbkeeper]

Thanks for you help mate

I took some of your ideas and put them into my code and got what i wanted.

Thanks

Josh