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CS449, Introduction to Systems Software, Spring 2007
TA : Ricardo Villamarín-Salomón
Lab
Exercise 1 Pointers, Arrays and pointer arithmetic
a) What does the program in Listing 1 do?
Listing 1 #include <stdio.h> #define NUM_ELEMS 7 int main() { int arr[NUM_ELEMS] = {5, 8, 10, 2, 9, 4, 1}; int *p, *pend; for (p=arr, pend=(p + NUM_ELEMS); p<pend; p++) printf("%d\n", *p); return 0; }
b) Does the program in Listing 2 do the same as the one in Listing 1?
Run it and see if you can explain the difference. What about the program in Listing
Listing 2 #include <stdio.h> #define NUM_ELEMS 7 int main() {
short int arr[NUM_ELEMS] = {5, 8, 10, 2, 9, 4, 1}; int *p, *pend; for (p=arr, pend=(p + NUM_ELEMS); p<pend; p++) printf("%d\n", *p); return 0; } Listing 3 #include <stdio.h> #define NUM_ELEMS 7 int main() { double arr[NUM_ELEMS] = {5.0, 8.0, 10.0, 2.0, 9.0, 4.0, 1.0}; float *p, *pend; for (p=arr, pend=(p + NUM_ELEMS); p<pend; p++) printf("%d\n", *p); return 0; }
Exercise 2 Structs^1
a. What will be the result of attempting to compile and run the following
program?
#include <stdio.h> typedef struct{ int x; int y; }INTEGERS; void manipulateIntegers( INTEGERS ); void printIntegers( INTEGERS ); int main() { INTEGERS i; i.x = 2; i.y = 3; printIntegers( i ); manipulateIntegers( i ); printIntegers( i ); } void printIntegers( INTEGERS i ) (^1) By Mohammad Hammoud
STUDENT s[2]; char *arr[2][3]= { {"MHH1", "123", "pgh"}, {"MHH2", "456", "pgh"} }; enrollStudent(&s[0], arr[0]); enrollStudent(&s[1], arr[1]); printDatabase( s); } void printDatabase( const STUDENT s[] ) { printf( "NAME\tID\tADDRESS\n\n"); int i; for( i = 0; i < 2; i++) printf( "%s\t%s\t%s\n", s[i].name, s[i].id, s[i].address ); } void enrollStudent( STUDENT *s, char *data[]) { s->name = data[0]; s->id = data[1]; s->address = data[2]; }
Exercise 3 Recursive functions and Pointer arithmetic^2
(Palindromes) A palindrome is a string that is spelled the same way forward and
backward. Some examples of palindromes are "radar" and "civic".
a. Write a recursive function testPalindrome that returns 1 if the string passed as a
constant parameter is a palindrome and 0 otherwise. For this exercise, you can
assume that the string passed contains only letters. You may use Listing 4 as a
starting point if you want.
b. Write a function testPalindromePtr that behaves in the same way that testPalindrome
but instead of receiving an entire string, just receives two pointers, one pointing to
the first character and the other to the last character of the part of the string that is
still unprocessed (do not use the [ ] operator). Use Listing 5 as a starting point.
Listing 4 #include <stdio.h> #include <string.h> int testPalindrome(const char string, int start, int end) { / write your code here */ } int main() { printf ("%d\n", testPalindrome("radar", 0, strlen("radar")-1)); printf ("%d\n", testPalindrome("saas", 0, strlen("saas")-1)); (^2) Modified from exercise 6.31, pg. 265 in the book
printf ("%d\n", testPalindrome("scifi", 0, strlen("scifi")-1)); return 0; } Listing 5 #include <stdio.h> #include <string.h> int testPalindromePtr(char *start, char end) { / write your code here */ } int main() { char *string; int strlength; string = "civic"; strlength = strlen(string); printf ("%d\n", testPalindromePtr( &string[0], &string[strlength-1] )); string = "saas"; strlength = strlen(string); printf ("%d\n", testPalindromePtr( &string[0], &string[strlength-1] )); string = "none"; strlength = strlen(string); printf ("%d\n", testPalindromePtr( &string[0], &string[strlength-1] )); return 0; }
