C Programming For The Absoloute Beginner Chapter 3 Challenge 2 Query

I've been working on this program for a good couple of weeks between my work hours.

The challenge in the book was:
Build a number guessing game that uses input validation (isdigit function) to verify that the user has entered a digit and not a non-digit (letter).

The following is the best I could come up with.

You'll notice that I ask the user to input their guess twice, once to assign to an integer and once to a character because I had no idea how to effectively convert the character to an integer.

This is the first proper game I have made with C so please feel free to point out any rookie errors :>

Any suggestions as to how to improve the code from here?

Cheers.

Code:

---

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

int main()

{
    int iRandomNum = 0;
    srand(time(NULL));
    char cResponse = '\0';
    int dResponse = 0;

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

    printf("iRandomNum= %d\n",iRandomNum);
    printf("please enter a digit\n");

    scanf("%c",&cResponse);
    printf("One more time?\n");
    scanf("%d",&dResponse);
    printf("cResponse= %c\n",cResponse);

if (isdigit (cResponse)==0)
    printf("letter was inserted, please enter a number next time\n");
else
    printf("iRandomNum= %d, this is a digit.\n",iRandomNum,", \n");


if (dResponse == iRandomNum)
    printf(" well done!");

else {
        printf("you lose\n");
        printf("You guessed cResponse= %c\n",cResponse);
        printf("You should have guessed %d",iRandomNum);}
}

---

Welcome to the forum. A couple of things for you:

Read How to define main FAQ

Did you not learn loops yet? Usually when you have input validation excersises it is part of a loop so that you keep asking until the input is correct.

Take a look at the atoi() function. That should allow you to clean up your code a little.

Code:

---

printf("iRandomNum= %d, this is a digit.\n",iRandomNum,", \n");

---

What exactly are you trying to do here? printf works like this:

printf([string to print, with %d and %s], [integer to replace %d], [string to replace %s])

When you use it, you have a string as your third argument, but you don't have a "%s" anywhere in the first.

Those are just artefacts that didn't get picked up in debugging.
Now that I have deleted them, it looks like this:
printf("iRandomNum= %d, this is a digit.\n", iRandomNum);
I use it to return the value f iRandomNum for debugging.

Currently trying to integrate atoi in so that I don't need to ask the user to input their answer twice.
Already made the program crash so that is proving fun to solve.

Code:

---

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

int main(void)

{
    int iRandomNum = 0;
    srand(time(NULL));
    char cResponse = '\0';
    int dResponse = 0;

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

    printf("iRandomNum= %d\n",iRandomNum);
    printf("please enter a digit\n");

    scanf("%c",&cResponse);
    printf("cResponse= %c\n",cResponse);


if (isdigit (cResponse)==0)
    printf("letter was inserted, please enter a number next time\n");
else
    printf("iRandomNum= %d, this is a digit.\n", iRandomNum);

dResponse = atoi(cResponse);
printf("%d",dResponse);

if (dResponse == iRandomNum)
    printf(" well done!");

else {
        printf("you lose\n");
        printf("You guessed cResponse= %c\n",cResponse);
        printf("You should have guessed %d",iRandomNum);}
}

---

Quote:

---

Originally Posted by Dekuben

Currently trying to integrate atoi in so that I don't need to ask the user to input their answer twice.
Already made the program crash so that is proving fun to solve.

Code:

---

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

int main(void)

{
    ....
dResponse = atoi(cResponse);
.....
}

---

---

Your compiler should be giving you errors with how you are using atoi(). It expects a C style string, not a single character. A couple of ways around this:

1. You could just pass the address of cResponse to atoi with &cResponse.
2. You could just do math to convert it to an integer: dResponse = cResponse - '0'.
3. You could setup a C style string, that way your program would be able to handle numbers that were entered >9. Look at the example on the atoi() page I pointed you to.

Also, as I mentioned before, did you not learn loops yet? Something like this for user input:

Code:

---

do
    ask user for a number
    store the number in a variable
loop while user input is not a number

---

I should read a bit from C Programming For the Absolut Beginner.


Quzah.

Quote:

---

Originally Posted by Dekuben

Currently trying to integrate atoi in so that I don't need to ask the user to input their answer twice.
Already made the program crash so that is proving fun to solve.

---

Like a hint?

Look up scanf() in your C library documentation. It will almost certainly have more information than your textbook... pay special attention to it's return value.

Now with that in mind... think about doing your inputs directly into an integer.

A little testing and you might be surprised how easy it is...