Solution for Exercise 19-12

#include <stdio.h>

int main()
{
    char sample[] = "From whence cometh my help?\n";
    char *ps;

    ps = sample;        /* initialize the pointer */

    while(*ps != '\0')
    {
        putchar(*ps);
        ps++;
    }
    return(0);
}

Output

From whence cometh my help?

Notes

* Unlike Listing 19-6 in the book, you don't need the index variable to make the code work; the ps pointer itself acts as an index.

* In Line 6 the pointer variable ps is created. At Line 8, it's assigned the address of string sample.

* A while loop works through the string, similar to the code in Listing 19-6. The while loop could have been written to use the index variable, in which case it could look like this:

while(*(ps+index) != '\0') { putchar(*(ps+index)); index++; }

*Refer to Table 19-2 (in the book) if you need a review on the *(a+n) format, but this approach defeats the purpose; the pointer itself is the index you can use to march through a string.

* One problem with incrementing the pointer (done in Line 13) is that the base address is lost. To re-work through the string, you must re-initialize pointer ps to the sample array.

Exercise ex1913 →