Newbie question. What am I doing wrong?

[kabuatama]

Hello. For my assignment, my teacher wants me to get 2 numbers from the user, and then valide them. He wants us to use getchar( ). I can get most of it to work using scanf, but using getchar messes everything up. Please help me out.

#include <stdio.h>



void main(void)

{        
         char str[256];
         int in_val,
             status;
         char skip_ch;
         int error;                           

    printf( "Please enter your name:\t " );
    gets(str);
    printf("Hello, %s\n", str);
   do { 
        
        
        error = 0;
        printf("Please enter an integer\t"); 
    in_val = getchar( );
   
    
    
    if (in_val != 1) {
               error = 1;
               scanf("%c", &skip_ch);
               printf("Invalid character, %c", skip_ch);
}
do
  scanf("%c", &skip_ch);
  while (skip_ch != '\n');
} 
while (error);

return (in_val);




    
           
system("Pause");                      




}

when using scanf, I did:

status = scanf("%d", &in_val);

Any ideas?

[bithub]

getchar() returns ASCII values. So if the user typed in "1", then getchar() would receive '1', not the integer value of 1.

int charVal = getchar();
int intVal = charVal - '0';

[kabuatama]

I'm sorry, I don't understand. I tried it like this:

   do { 
        
        
        error = 0;
        printf("Please enter an integer\t"); 
    int charVal = getchar();
    int intVal = charVal - '0';
   
    
    
    if (intVal != 1)

...

but it doesn't work. It brings up the invalid character message every time.

[Dave_Sinkula]

FAQ > How do I... (Level 1) > How do I get a number from the user (C)

[kabuatama]

I understand how to store the number using getchar (). The problem I am having is validating the number when using getchar (). This is what I need help with. Thank you for helping, though.

[filker0]

Look up the header file ctype.h... There is a function/macro (depends on the compiler) defined called isdigit() that might be helpful.

Also know that the ascii characters for '0' through '9' are consecutive, so a character that is < '0' or > '9' is not a decimal digit.

[kabuatama]

isdigit( ) did help, and I seem to have the numbers working (I just hope I did it correctly). This is what I have so far:

         char str[256];
         int start;      
         int num;
         int numb;
         

    printf( "Please enter your name:\t " );
    gets(str);
    printf("Hello, %s\n\n", str);
  
        
        
        
        printf("Please enter two numbers between 0 and 9.\t"); 
    num = getchar ( );
   numb = getchar ( );
        if (isdigit (num))

   printf("First number is valid!\n");
   else printf ("Your first entry was not a number.\n");
   
   
       if (isdigit (numb))
   printf ("The second number is valid!\n");
  else 
       printf("The second entry was not a number.\n");


if (num > numb)
printf("The first number is greater!\n");

if (num < numb) 
printf("The second number is greater!\n");

if (num == numb)
printf("You entered the same number twice!\n");

Now, I want it so that if either or both entries are not numbers, the program will ask for 2 more numbers. I assume there is a return value that can be used for this, but am not quite sure how this works.


There are a few more parts to this that I need help with. I also need it to compare the numbers, and find out which one is smaller. Also, I need to print out all the numbers, starting with the smaller, between the two numbers entered. Any help would be greatly appreciated. Thanks.


Edit:

I figured out how to tell which number is greater, and I added it above. I still need help with the return, and printing the numbers between the two numbers....entered? I'm still not sure what that means.

[Salem]

Sorry, but until you fix your teacher, helping you is a waste of time because nothing good we say will ever be used by you or your teacher.

[kabuatama]

I've gotten most of it figured out. What I need help with is printing all the numbers between the numbers entered. This means that if the two numbers entered were "2" and "5," 3 and 4 would print out. This is what I have so far for this section:

  for ( x = 0; x < 10;) 
  
  { 
      if (x < num)
      x++;
      if (x < numb)
      x++;
  if (x > num) {
        printf ("%d\n", x);
        x++; }
        else if (x > numb) {
             printf ("%d\n", x);
        x++; }
        
        }

it doesn't seem to work. I am guessing that I am using something wrong. Thanks if you can help.

[dwks]

Does this help?

int x, low, high;
scanf("%i %i", &low, &high);
for(x = low; x < high; x ++)
    printf("%i\n", x);
}

(%i is the same as %d.)

Don't use gets(). Nor void main(). Perferably not system("pause"), either.