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2008-11-03T05:19:11Z

37 revision(s)

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This second lab is primarily based on pointers.

===Task 1===
#include <stdio.h>
int main(){
int *ip;
printf("%d\n", sizeof(ip));
}

Size of all pointers no matter the data type or OS, they all had the same value of 4.
I thought the value will vary in Linux but guess it doesnt.

===Task 2===
In task 2 we had to declare two variables x and y and print out their addresses and also the difference between these addresses 

#include <stdio.h>
int main(void){
int x;
int y;
printf("&x=%p,&y=%p,diff=%ld\n",&x,&y,(long)(&x-&y));
printf("&x=%p,&y=%p,diff=%ld\n",&x,&y,((long)&x-(long)&y));
}

For Windows: 
&x=0023FDB0 &y=0023FDA4 diff=3 
&x=0023FDB0 &y=0023FDA4 diff=12 

For Linux: 
&x = 0xffa75710 &y = 0xffa7570c, difference = 1 
&x = 0xffa75710 &y = 0xffa7570c, difference = 4 
Note: Had some problems getting into linux as my pc didnt bring up my home drive so had to look at neighbours comp.

===Task 3===
In task 3 we introduce the statement char arr[4] between the x and y variables.
#include <stdio.h>
int main(void){
int x;
char arr[4];
int y;
printf("enter needed statement here",)
}

Using Windows,we had to find:
*Sizeof array: 4
*Address of array: 0012FF54
*Value of &arr:1245012
*Value of arr+4:1245016
*Value of &arr[4]:1245016

Varying the size of the array from 0 to 10, and recording the difference between &x and &y.

#include <stdio.h>
int main(){
int x;
char arr["enter number here"];
int y;
printf("&x=%p,&y=%p,diff=%ld\n",&x,&y,(long)(&x-&y));
printf("&x=%p,&y=%p,diff=%ld\n",&x,&y,((long)&x-(long)&y));
} 

Array sizes and their differences: 
0|Not Applicable 
1|6,24 
2|6,24 
3|6,24 
4|6,24 
5|7,28 
6|7,28 
7|7,28 
8|7,28 
9|8,32 
10|8,32 
Note: No results for linux due to me having technical issues.

Next step is reverting back to array size 4 and setting x and y to 0 and arr[4] to 10 and printing out values

#include <stdio.h>
int main(){
int x=0;
char arr[4] = {10};
int y=0;
printf("Value of x=%d\nValue of y=%d\n", x, y);
} 

x=0 
y=0 
Note: not sure if its correct.

===Task 4===
Declaring x and y as global variables.

#include <stdio.h>
int y;
int x;
int main(){
char arr["enter number here"];
printf("&x=%p,&y=%p,diff=%ld\n",&x,&y,(long)(&x-&y));
printf("&x=%p,&y=%p,diff=%ld\n",&x,&y,((long)&x-(long)&y));
} 

Array sizes and their differences: 
0|Not Applicable 
1|1,4 
2|1,4 
3|1,4 
4|1,4 
5|1,4 
6|1,4 
7|1,4 
8|1,4 
9|1,4 
10|1,4 
Note:Are the results meant to be the same??Also i get different results on different computers which is expected i suppose. 

===Task 5===
int *p1, *p2;
{ int q; p1 = &q; }
{ int r; p2 = &r; } 

I think the values of p1 and p2 will be whatever the address if q and r are since they will be pointing at p and q respectively. 

===Task 6===
Program woudnt compile in visual studio.

===Task 7===
#include <stdio.h>
struct {
char my_char;
short my_short;
int my_int;
long my_long;
float my_float;
double my_double;
} my_struct;
int main ()
{
printf( "&my struct = %p\n", my_struct );
printf( "offsets:\n"
"my_char: %ld\n"
"my_short: %ld\n"
"my_int: %ld\n"
"my_long: %ld\n"
"my_float: %ld\n"
"my_double: %ld\n",
(long)&my_struct - (long)&my_struct.my_char,
(long)&my_struct - (long)&my_struct.my_short,
(long)&my_struct - (long)&my_struct.my_int,
(long)&my_struct - (long)&my_struct.my_long,
(long)&my_struct - (long)&my_struct.my_float,
(long)&my_struct - (long)&my_struct.my_double );
} 

Results: 
offsets: 
my_char: 0 
my_short: -2 
my_int: -4 
my_long: -8 
my_float: -12 
my_double: -16 

===Task 8===

#include <stdio.h>
union {
char my_char;
short my_short;
int my_int;
long my_long;
float my_float;
double my_double;
} my_union;
int main ()
{
printf( "&my struct = %p\n", my_union );
printf( "offsets:\n"
"my_char: %ld\n"
"my_short: %ld\n"
"my_int: %ld\n"
"my_long: %ld\n"
"my_float: %ld\n"
"my_double: %ld\n",
(long)&my_union - (long)&my_union.my_char,
(long)&my_union - (long)&my_union.my_short,
(long)&my_union - (long)&my_union.my_int,
(long)&my_union - (long)&my_union.my_long,
(long)&my_union - (long)&my_union.my_float,
(long)&my_union - (long)&my_union.my_double );
} 

Results from using union: 
offsets: 
my_char: 0 
my_short: 0 
my_int: 0 
my_long: 0 
my_float: 0 
my_double: 0 

===Task 9===

#include <stdio.h>
int main()
{
char *sp1, *sp2, *sp3;
sp1 = malloc( 10 );
printf("sp1=%p\n",sp1);
sp2 = malloc( 10 );
printf("sp2=%p\n",sp2);
free( sp1 );
sp3 = malloc( 10 );
printf("sp3=%p\n",sp3);
printf("sp1=%p\n",sp1);
} 

Results (windows): 
sp1=00924B28 
sp2=00922288 
sp3=009222C0 
sp1=00924B28 
Results(linux): 
sp1= 0xff809728 
sp2= 0xff809724 
sp3= 0xff809720 
sp1= 0xff809728

SE250:lab-2:srag014 - Revision history

Mark: 37 revision(s)