CSc 265 - Lab Exercise 4

Team Name:

Team Members:





contents of file "intersection.c":

#include <stdio.h>

int findpos(int a[],int n,int x)
{
	int i;

	for (i = 0; i < n; i++)
		if (a[i] == x) return i;
	return -1;
}

void shiftleft(int a[],int startpos,int endpos)
{
	int i;
	
	for (i = startpos; i < endpos; i++)
		a[i] = a[i+1];
}

void intersection(int a[],int *alen,int b[],int blen)
{
	int i;

	for (i = *alen-1; i >= 0; i--) {
		if (findpos(b,blen,a[i]) == -1) {
			shiftleft(a,i,*alen-1);
			(*alen)--;
		}
	}
}

main()
{
	int a[] = {1,3,5,7,9};
	int alen = 5;
	int b[] = {1,5,9};
	int blen = 3;
	int i;

	intersection(a,&alen,b,blen);
	for (i = 0; i < alen; i++)
		printf("a[%d]: %d ",i,a[i]);
	printf("\n");

	abort();
}



To the left is the corrected code from last week's exercise, which computes
the intersection of the arrays a[] and b[], stores it in a[], then
outputs the contents of a[]. The abort() function call at the end of
the main function causes the program to generate a core dump, which
is required for the dbx debugger. For the questions below, assume the 
following commands have been executed:

        cc -g -o intersection intersection.c
        unlimit coredumpsize
        intersection
        dbx intersection core 

What is the result of entering the following commands (questions 1-5)?
1) whatis a



2) whereis i



3) which i



4) print a[0]*10 - b[2]



5) &a/5D



6) How would you display the source code for the intersection function?



7) How could you display the contents of the array a[] (5 elements) plus the
   contents of the 8 bytes immediately following a[]?



8) What sequence of commands would you use to run the program and stop
   execution after the 7 has been eliminated from a[] and then display 
   the contents of the 4th element of a[]? (Hint: use stop in [functionname])










9) What sequence of commands would you use to run the program and generate
   trace output every time the variable alen is changed? How many times does
   this occur?