Beginner C Question Help

pmacdonald · 07-10-2009, 10:16 PM

I'm currently reading C Programming for the Absolute Beginner and am stuck on one of the chapter questions. This is a really simple question but I am stuck.

Problem:
Build a number guessing game that uses input validation (isdigit() funciton) to verify that the user has entered a digit and not a non-digit (letter). Store a random number between 1 and 10 into a variable each time the program is run. Prompt the user to guess a number between 1 and 10 and alert the user if he was correct or not.

Code:

#include <stdio.h>
#include <ctype.h>

main()
{

    int iNumber = 0;
    int iAnswer = 0;
    srand(time());

    iAnswer = (rand() % 10) + 1;

    printf("Guessing Game\n");
    printf("\nGuess a number from 1 to 10: ");
    scanf("%d", &iNumber);

    if ( isdigit(iNumber) > 10 || < 1 )
        printf("Enter a number between 1 and 10");

        if (iNumber == iAnswer)
            printf("\nYou guessed right!\n");

        else
            printf("\nSorry, you guessed wrong\n");
            printf("The correct guess was %d\n", iAnswer);
}

I've already tried to run the program and debug it with no luck. I'm missing something from the text and obviously didn't apply that here.

Any help will be greatly appreciated,

-Peter

BEN10 · 07-10-2009, 10:35 PM

Quote:

Originally Posted by pmacdonald

I'm currently reading C Programming for the Absolute Beginner and am stuck on one of the chapter questions. This is a really simple question but I am stuck.

Problem:
Build a number guessing game that uses input validation (isdigit() funciton) to verify that the user has entered a digit and not a non-digit (letter). Store a random number between 1 and 10 into a variable each time the program is run. Prompt the user to guess a number between 1 and 10 and alert the user if he was correct or not.

Code:

#include <stdio.h>
#include <ctype.h>

main()
{

    int iNumber = 0;
    int iAnswer = 0;
    srand(time());

    iAnswer = (rand() % 10) + 1;

    printf("Guessing Game\n");
    printf("\nGuess a number from 1 to 10: ");
    scanf("%d", &iNumber);

    if ( isdigit(iNumber) > 10 || < 1 )
        printf("Enter a number between 1 and 10");

        if (iNumber == iAnswer)
            printf("\nYou guessed right!\n");

        else
            printf("\nSorry, you guessed wrong\n");
            printf("The correct guess was %d\n", iAnswer);
}

I've already tried to run the program and debug it with no luck. I'm missing something from the text and obviously didn't apply that here.

Any help will be greatly appreciated,

-Peter

To check correctly do this

Code:

isdigit(iNumber) > 10 || isdigit(iNumber)< 1

**Salem** · 07-10-2009, 10:50 PM

isdigit() is for chars, not ints.

> scanf("%d", &iNumber);
You can't use isdigit here, scanf has already done that for you with the %d conversion.

If you did this however

Code:

char ch;
scanf("%c",&ch);
if ( isdigit(ch) )

Then that would be better usage of the function.

Sebastiani · 07-10-2009, 10:50 PM

>> if ( isdigit(iNumber) > 10 || < 1 )

Do be sure to look up the documentation on a function before you use it.

Anyway, isdigit expects a *character* value and returns true or false (1 or 0). As it turns out you don't need the function at all here, just a straight comparison:

Code:

if ( iNumber > 10 || iNumber < 1 )

Next, this statement:

Code:

printf("The correct guess was %d\n", iAnswer);

If you want it to execute on the else condition, you'll need to enclose everything from the block in brackets, eg:

Code:

if ( iNumber > 10 || iNumber < 1 ) 
{
        printf("Enter a number between 1 and 10");
}
else
{
        if (iNumber == iAnswer)
        {
		printf("\nYou guessed right!\n");
	}
        else
        {
		printf("\nSorry, you guessed wrong\n");
		printf("The correct guess was %d\n", iAnswer);
	}
}

EDIT: Ah, now I see isdigit is part of the requirements. In that case, declare a character and pass it to scanf with the %c format specifier.

pmacdonald · 07-11-2009, 12:41 AM

Thanks for the quick replies and clarifications. I had a hunch that I was using the isdigit function wrong.

pmacdonald · 07-11-2009, 09:49 AM

A few more questions arose. How do I correctly call char cResponse to see if it is equal to the integer iAnswer?

This code turned up many error in; srand, time, and rand.

Any ideas?

Code:

#include <stdio.h>
#include <ctype.h>

main()
{

    char cResponse = '\0';
    int iAnswer = 0;
    srand(time());

    iAnswer = (rand() % 10) + 1;

    printf("Guessing Game\n");
    printf("\nGuess a number from 1 to 10: ");
    scanf("%c", &cResponse);

    if isdigt(cResponse) > 10 || isdigit(cResponse) < 1
    {
        printf("Enter a number between 1 and 10");
    }
    else
    {
        if (cResposne == iAnswer)
        {
            printf("\nYou guessed right!\n");
        }
        else
        {
            printf("\nSorry, you guessed wrong\n");
            printf("The correct guess was %d\n", iAnswer);
        }
    }
}

Elysia · 07-11-2009, 10:33 AM

Must must return int.
Missing ( and ) around the if.

**Salem** · 07-11-2009, 12:12 PM

> if isdigt(cResponse) > 10 || isdigit(cResponse) < 1
isdigit() is a TRUE/FALSE deal.

isdigit('0') returns true (a non-zero result)
isdigit('A') returns false (zero)

pmacdonald · 07-11-2009, 12:15 PM

Please be more specific...around which if? I added them around the isdigit function and I still got the errors. I'm also not sure that I can compare the character to the integer so how would I do this yet still incorporate isdigit into the program?

Errors:
warning: return type default to 'int'
In function 'main':
warning: implicit declaration of function 'srand'
warning: implicit declaration of function 'time'
warning: implicit declaration of function 'rand'
error: syntax error before "isdigit"

msh · 07-11-2009, 12:24 PM

For starters, you're missing an include.

#include <stdlib.h>

That error is responsible for half your warnings.

Elysia · 07-11-2009, 12:43 PM

if isdigt(cResponse) > 10 || isdigit(cResponse) < 1
^ Missing ( and ).
EVERY if must begin with ( and end with ).
And as Salem points out, isdigit checks if the response is a digit or not. It doesn't check the range of a number, like if it's > 10.
Isdigit is like asking "is this a digit?" and it responds yes or no.

pmacdonald · 07-11-2009, 01:02 PM

msh - mmh, the book hasn't gone over that yet so there should be a way to make this program without incorporating it. I tried to add it but got the following errors:
warning: return type defaults to 'int'

In function 'main':
warning: implicit declaration of function 'time'
error: 'cResponse' undeclared (first sue in this function)
error: (Each undeclared identifier is reported only once

Elysia - I added the ( ) but still have errors.

So how do I incorporate isdigit into this program without having it compare numbers. As Elysia pointed out the function if isdigit(cResponse) > 10 || isdigit(cResponse) < 1 wouldn't even serve its pupose...correct?

Elysia · 07-11-2009, 01:08 PM

>>warning: return type defaults to 'int'
Main must return int. I posted a link earlier (red text). Read it. Very informative.

>>warning: implicit declaration of function 'time'
"Implicit declaration" means you used a function without first declaring it. That means, in this case, that you didn't include the correct header. You must include time.h.

As for the rest...
You should really think about the logic of your program.
In psuedo code, you want to do:

Check if answer is a digit.
Check if answer is in range 0 > x < 10.

How do you do this?
Can you answer those questions?
Think about it. You should be able to at least do the second.

itCbitC · 07-11-2009, 01:11 PM

Did you read Salems' post at all??

tabstop · 07-11-2009, 01:11 PM

Well, your book can't have mentioned rand without doing stdlib.

Food for thought: If isdigit returns true/false, why do you need to compare it with anything to make a true/false decision?

07-10-2009, 10:16 PM	#1
pmacdonald Registered User Join Date: Jul 2009 Posts: 10	Beginner C Question Help I'm currently reading C Programming for the Absolute Beginner and am stuck on one of the chapter questions. This is a really simple question but I am stuck. Problem: Build a number guessing game that uses input validation (isdigit() funciton) to verify that the user has entered a digit and not a non-digit (letter). Store a random number between 1 and 10 into a variable each time the program is run. Prompt the user to guess a number between 1 and 10 and alert the user if he was correct or not. Code: #include <stdio.h> #include <ctype.h> main() { int iNumber = 0; int iAnswer = 0; srand(time()); iAnswer = (rand() % 10) + 1; printf("Guessing Game\n"); printf("\nGuess a number from 1 to 10: "); scanf("%d", &iNumber); if ( isdigit(iNumber) > 10 \|\| < 1 ) printf("Enter a number between 1 and 10"); if (iNumber == iAnswer) printf("\nYou guessed right!\n"); else printf("\nSorry, you guessed wrong\n"); printf("The correct guess was %d\n", iAnswer); } I've already tried to run the program and debug it with no luck. I'm missing something from the text and obviously didn't apply that here. Any help will be greatly appreciated, -Peter
pmacdonald is offline

07-10-2009, 10:50 PM	#3
Salem and the hat of vanishing Join Date: Aug 2001 Location: The edge of the known universe Posts: 21,214	isdigit() is for chars, not ints. > scanf("%d", &iNumber); You can't use isdigit here, scanf has already done that for you with the %d conversion. If you did this however Code: char ch; scanf("%c",&ch); if ( isdigit(ch) ) Then that would be better usage of the function. __________________ If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut. Up to 8Mb PlusNet broadband from only £5.99 a month!
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07-10-2009, 10:50 PM	#4
Sebastiani Guest Join Date: Aug 2001 Posts: 4,922	>> if ( isdigit(iNumber) > 10 \|\| < 1 ) Do be sure to look up the documentation on a function before you use it. Anyway, isdigit expects a character value and returns true or false (1 or 0). As it turns out you don't need the function at all here, just a straight comparison: Code: if ( iNumber > 10 \|\| iNumber < 1 ) Next, this statement: Code: printf("The correct guess was %d\n", iAnswer); If you want it to execute on the else condition, you'll need to enclose everything from the block in brackets, eg: Code: if ( iNumber > 10 \|\| iNumber < 1 ) { printf("Enter a number between 1 and 10"); } else { if (iNumber == iAnswer) { printf("\nYou guessed right!\n"); } else { printf("\nSorry, you guessed wrong\n"); printf("The correct guess was %d\n", iAnswer); } } EDIT: Ah, now I see isdigit is part of the requirements. In that case, declare a character and pass it to scanf with the %c format specifier.
Sebastiani is offline

07-11-2009, 12:41 AM	#5
pmacdonald Registered User Join Date: Jul 2009 Posts: 10	Thanks for the quick replies and clarifications. I had a hunch that I was using the isdigit function wrong.
pmacdonald is offline

07-11-2009, 12:12 PM	#8
Salem and the hat of vanishing Join Date: Aug 2001 Location: The edge of the known universe Posts: 21,214	> if isdigt(cResponse) > 10 \|\| isdigit(cResponse) < 1 isdigit() is a TRUE/FALSE deal. isdigit('0') returns true (a non-zero result) isdigit('A') returns false (zero) __________________ If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut. Up to 8Mb PlusNet broadband from only £5.99 a month!
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07-11-2009, 12:15 PM	#9
pmacdonald Registered User Join Date: Jul 2009 Posts: 10	Please be more specific...around which if? I added them around the isdigit function and I still got the errors. I'm also not sure that I can compare the character to the integer so how would I do this yet still incorporate isdigit into the program? Errors: warning: return type default to 'int' In function 'main': warning: implicit declaration of function 'srand' warning: implicit declaration of function 'time' warning: implicit declaration of function 'rand' error: syntax error before "isdigit"
pmacdonald is offline

07-11-2009, 12:24 PM	#10
msh Novice Join Date: Jul 2009 Posts: 32	For starters, you're missing an include. #include <stdlib.h> That error is responsible for half your warnings.
msh is offline

07-11-2009, 01:02 PM	#12
pmacdonald Registered User Join Date: Jul 2009 Posts: 10	msh - mmh, the book hasn't gone over that yet so there should be a way to make this program without incorporating it. I tried to add it but got the following errors: warning: return type defaults to 'int' In function 'main': warning: implicit declaration of function 'time' error: 'cResponse' undeclared (first sue in this function) error: (Each undeclared identifier is reported only once Elysia - I added the ( ) but still have errors. So how do I incorporate isdigit into this program without having it compare numbers. As Elysia pointed out the function if isdigit(cResponse) > 10 \|\| isdigit(cResponse) < 1 wouldn't even serve its pupose...correct?
pmacdonald is offline

07-11-2009, 01:11 PM	#14
itCbitC Registered User Join Date: Oct 2008 Location: TX Posts: 1,262	Did you read Salems' post at all??
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07-11-2009, 01:11 PM	#15
tabstop and the Hat of Guessing Join Date: Nov 2007 Posts: 8,740	Well, your book can't have mentioned rand without doing stdlib. Food for thought: If isdigit returns true/false, why do you need to compare it with anything to make a true/false decision?
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