Thread: Need some explanation conserning this code, (char arrays and pointers)

Greetings EveryOne

Look at this code;

Code:

#include <stdio.h>

char StringA[] = "Hello, I am Laythe.";
char StringB[30];

int main()
{
    char *PointerA;
    char *PointerB;

    printf("puts(StringA) =\n");
    puts(StringA);  // Prints StringA on the screen;
    printf("\n");

    PointerA = StringA;

    printf("puts(PointerA) = \n");
    puts(PointerA);
    printf("\n");

    PointerB = StringB; // Line 21;

    while(*PointerA != '\0')
    {
        *PointerB++ = *PointerA++;
    }
    *PointerB = '\0';

    printf("puts(StringB) = \n");
    puts(StringB);
    printf("\n");

    PointerB = StringB; // Line 33;

    printf("puts(PointerB) = \n");
    puts(PointerB);

    return 0;
}

- At line 21, if you comment it or delete it, the compiler will stop compiling at the line.
why is that?

* don't forget to return line 21 as it was if you modified it.

- At line 33, if you comment it or delete it, the value of PointerB is null.
why is that?

* compile the same code with some modifications and you will get a run time error, can you tell me why?

Code:

#include <stdio.h>

char StringA[] = "Hello, I am Laythe.";
char StringB[30];

int main()
{
    char *PointerA;
    char *PointerB;

    printf("puts(StringA) =\n");
    puts(StringA);  // Prints StringA on the screen;
    printf("\n");

    PointerA = StringA;

    printf("puts(PointerA) = \n");
    puts(PointerA);
    printf("\n");

    PointerB = StringB; // Line 21;

    while(*PointerA != '\0')
    {
        *PointerB++ = *PointerA++;
    }
    *PointerB = '\0';

    printf("puts(StringB) = \n");
    puts(StringB);
    printf("\n");

    PointerB = StringB; // Line 33;

    printf("puts(PointerB) = \n");
    puts(PointerB);
    printf("\n");
    printf("*PointerB = %s", *PointerB);

    return 0;
}

Thank You In Advance

Originally Posted by Elysia

This is all C, isn't it? Yet, why is it in the C++ section?

Because for the moment there seems to be a bug in the forum software...

When you click on "C Programming" you end up in the C++ section...

yes am absolutely facing that bug in the forum.
trying to post in C forum but ending up on C++ forum.

anyway, might someone help me with my problem please.

> - At line 21, if you comment it or delete it, the compiler will stop compiling at the line.
> why is that?
Have you tried it with your compiler?
Did you get any messages?
Did it actually stop compiling (with an error, as opposed to a warning)?

yes i have tried it with my compiler of course
i get no error or warning, when the code is run it stops outputting at line 21 and getting this in the building log: Process terminated with status -1073741819 (0 minutes, 47 seconds).
*instead of getting "Process terminated with status 0"

> - At line 33, if you comment it or delete it, the value of PointerB is null.
> why is that?
That depends, does your tutor know the difference between nul and NULL?
ptr == NULL is one thing
*ptr == '\0' is a completely different thing.
Which do you mean?

i am self-tutoring, and i have read about the difference between NULL and nul.
why don't u run this and see what i'm talking about concerning NULL.

Code:

#include <stdio.h>

char StringA[] = "Hello, I am Laythe.";
char StringB[30];

int main()
{
    char *PointerA;
    char *PointerB;

    printf("puts(StringA) =\n");
    puts(StringA);  // Prints StringA on the screen;
    printf("\n");

    PointerA = StringA;

    printf("puts(PointerA) = ");
    puts(PointerA);
    printf("\n");

    PointerB = StringB; // Line 21;

    while(*PointerA != '\0')
    {
        *PointerB++ = *PointerA++;
    }
    *PointerB = '\0';

    printf("puts(StringB) = \n");
    puts(StringB);
    printf("\n");

    //PointerB = StringB; // Line 33;

    printf("puts(PointerB) = ");
    puts(PointerB);
    //printf(*PointerB);
    printf("\n");
    printf("*PointerB = %s", *PointerB);

    return 0;
}

P.S: as I mentioned, I'm self-learning to program so I'm analysing everything I read and code so I can have a deep understanding of programming.

Any help would be so very much appreciated cos the only tutor I can have is articles from the net and your help on the forum, Thank You.