Thread: Help: prevent program from crashing by entering non numerical value.

When I enter a non-numerical value, the program crashes. How do I stop this? Also, my error msg does not display when I hit option other than 1 or 2 (><)
Here is the code:

PHP Code:

#include <stdio.h>


int main(void)
{
    
    float original_temp, new_temp;
    int option;
    
    
    printf("Enter the value you wish to convert.\n");
    scanf("%f", &original_temp);
    
    
    
    do{
    printf("You entered %.5f. \n", original_temp);
    printf("Now, what is the unit of measurment of the value you just entered please type 1 or 2:\n"
            "1. Fahrenheit\n"
            "2. Celsius\n");
    
    scanf("%d", &option);
    } while(option!=1 && option!=2);

    
        if(option==1)
        {
        printf("You have %.5f degrees Fahrenheit.\n",original_temp );
        new_temp = (((original_temp - 32) / 9) * 5);
        printf("When converted to degrees Celsius you get %.5f degrees Celsius\n", new_temp);
        }
        
        
        else if(option==2) 
        {
        printf("You have %.5f degrees Celsius.\n", original_temp);
        new_temp = (((original_temp / 5) * 9) + 32);
        printf("When converted to degrees Fahrenheit you get %.5f degrees Fahrenheit\n", new_temp);
        }
        
        else
        {
        printf("Error\n");
        }
    
        
    
return 0;     
} 


Add this:

Code:

getchar();

right after the scanf() line of code. That will pull off the newline that scanf() leaves behind on the keyboard buffer. Leaves the input stream "cleaned" if the user has not run wild.

Code:

fgets(mycharArray, sizeof(mycharArray), stdin);

is a much more robust method. Then you can test mycharArray[0] -'0' for your int's value. fgets() doesn't allow buffer overflows.