Review Questions

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Review Questions

1. What's wrong with this attempted declaration of a character string?

    int main(void) {    char name[] = {`F', `e', `s', `s' };    ... } 

2. What will this program print?

    #include <stdio.h> int main(void) {    char note[] = "See you at the snack bar.";    char *ptr;    ptr = note;    puts(ptr);    puts(++ptr);    note[7] = ` 
     #include <stdio.h> int main(void) { char note[] = "See you at the snack bar."; char *ptr; ptr = note; puts(ptr); puts(++ptr); note[7] = `\0'; puts(note); puts(++ptr); return 0; }  
    ';    puts(note);    puts(++ptr);    return 0; } 

3. What will this program print?

    #include <stdio.h> #include <string.h> int main(void) {    char food[] = "Yummy";    char *ptr;    ptr = food + strlen(food);    while (--ptr >= food)         puts(ptr);    return 0; } 

4. What will the following program print?

    #include <stdio.h> #include <string.h> int main(void) {     char goldwyn[40] = "art of it all ";     char samuel[40] = "I read p";     char *quote = "the way through.";     strcat(goldwyn, quote);     strcat(samuel, goldwyn);     puts(samuel);     return 0; } 

5. Here is an exercise providing practice with strings, loops , pointers, and pointer incrementing. First, suppose you have this function definition:

    #include <stdio.h> char *pr (char *str) {   char *pc;   pc = str;   while (*pc)      putchar(*pc++);   do {      putchar(*pc);      } while (pc - str);   return (pc); } 

   Consider the following function call:

    pr("Ho Ho Ho!"); 

   1. What is printed?

   2. What type should x be?

   3. What value does x get?

   4. What does the expression *--pc mean, and how is it different from --*pc ?

   5. What would be printed if *--pc were replaced with *pc-- ?

   6. What do the two while expressions test for?

   7. What happens if pr() is supplied with a null string as an argument?

   8. What must be done in the calling function so that pr() can be used as shown?

6. How many bytes does `$' use? What about "$" ?

7. What does the following program print?

    #include <stdio.h> #include <string.h> #define M1  "How are ya, sweetie? " char M2[40] = "Beat the clock."; char * M3 = "chat"; int main(void) {      char words[80];      printf(M1);      puts(M1);      puts(M2);      puts(M2 + 1);      strcpy(words,M2);      strcat(words, " Win a toy.");      puts(words);      words[4] = ` 
     #include <stdio.h> #include <string.h> #define M1 "How are ya, sweetie? " char M2[40] = "Beat the clock."; char * M3 = "chat"; int main(void) { char words[80]; printf(M1); puts(M1); puts(M2); puts(M2 + 1); strcpy (words,M2); strcat(words, " Win a toy."); puts(words); words[4] = `\0'; puts(words); while (*M3) puts(M3++); puts(--M3); puts(--M3); M3 = M1; puts(M3); return 0; }  
    ';      puts(words);      while (*M3)         puts(M3++);      puts(--M3);      puts(--M3);      M3 = M1;      puts(M3);      return 0; } 

8. What does the following program print?

    #include <stdio.h> int main(void) {     static char str1[] = "gawsie";     static char str2[] = "bletonism";     char *ps;     int i = 0;     for (ps = str1; *ps != ` 
     #include <stdio.h> int main(void) { static char str1[] = "gawsie"; static char str2[] = "bletonism"; char *ps; int i = 0; for (ps = str1; *ps != `\0'; ps++) { if (*ps == `a'  *ps == `e') putchar(*ps); else (*ps)--; putchar(*ps); } putchar(`\n'); while (str2[i] != `\0') { printf("%c", i % 3 ? str2[i] : `*'); ++i; } return 0; }  
    '; ps++) {          if (*ps == `a'  *ps == `e')                 putchar(*ps);          else                 (*ps)--;          putchar(*ps);         }     putchar(`\n');     while (str2[i] != ` 
     #include <stdio.h> int main(void) { static char str1[] = "gawsie"; static char str2[] = "bletonism"; char *ps; int i = 0; for (ps = str1; *ps != `\0'; ps++) { if (*ps == `a'  *ps == `e') putchar(*ps); else (*ps)--; putchar(*ps); } putchar(`\n'); while (str2[i] != `\0') { printf("%c", i % 3 ? str2[i] : `*'); ++i; } return 0; }  
    ') {        printf("%c", i % 3 ? str2[i] : `*');        ++i;        }     return 0; } 

9. The strlen() function takes a pointer to a string as an argument and returns the length of the string. Write your own version of this function.

10. Design a function that takes a string pointer as argument and returns a pointer to the first space character in the string on or after the pointed-to position. Have it return a null pointer if it finds no spaces.

11. Rewrite Listing 11.17 using ctype .h functions so that the program recognizes a correct answer regardless of the user 's choice of uppercase and lowercase.

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