Question

I am learning about C pointers by creating various simple functions. I have just created a function to reverse a char array. It works, but after the output it also displays a bunch of garbage chars (see screenshot below).

Here’s my code:

void reverseString();

int main()
{
    reverseString();

    system("PAUSE");
    return 0;
}

void reverseString()
{
    char string1[20], string2[20];
    char *ptr1, *ptr2;
    ptr1 = &string1[0];
    ptr2 = &string2[0];

    printf("Enter string: \n");
    scanf("%s", string1);

    int len1 = strlen(string1);

    int i;
    for (i = 0; i < len1; i++)
    {
        ptr2[i] = ptr1[len1 - i - 1];
    }

    printf("%s\n", string2);
}

How can I get rid of the garbage chars? Is there something wrong with my code or did I just nto account for something or what?

Answer 1

You forgot to nul-terminate the new string:

int i;
for (i = 0; i < len1; i++)
{
    ptr2[i] = ptr1[len1 - i - 1];
}

//  Add this
ptr2[i] = '\0';

---

When you print a char*, it will keep reading until it finds that nul character. But since you left it out, it kept going and going…