CSC231 Mini Lab 1 Solution and Discussion
--D. Thiebaut 09:38, 12 September 2012 (EDT)
Solution 1
;;; minilab1_v1.asm
;;; D. Thiebaut
;;; prints this string on the screen:
;;;
;;; *********************************
;;; * Welcome to CSC231 *
;;; * Home of the Assembly Language *
;;; *********************************
section .data
msg db "*********************************", 10
db "* Welcome to CSC231 *", 10
db "* Home of the Assembly Language *", 10
db "*********************************", 10, 10
msgLen equ $-msg
section .text
global _start
_start:
mov eax,4
mov ebx,1
mov ecx,msg
mov edx,msgLen
int 0x80
;;; exit
mov eax,1
mov ebx,0
int 0x80
Solution 2
;;; minilab1_v2.asm
;;; D. Thiebaut
;;; prints this string on the screen:
;;;
;;; *********************************
;;; * Welcome to CSC231 *
;;; * Home of the Assembly Language *
;;; *********************************
section .data
msg db "*********************************", 10
msgLen1 equ $-msg
db "* Welcome to CSC231 *", 10
db "* Home of the Assembly Language *", 10
msgLen2 equ $-msg
section .text
global _start
_start:
;;; print first 3 lines
mov eax,4
mov ebx,1
mov ecx,msg
mov edx,msgLen2
int 0x80
;;; print first line back, to close box
mov eax,4
mov ebx,1
mov ecx,msg
mov edx,msgLen1
int 0x80
;;; exit
mov eax,1
mov ebx,0
int 0x80
What is the trade-off?
- Generate the listing of the assembly:
nasm -f elf -F stabs -l minilab1_v1.lst minilab1_v1.asm (that's a minus ell option in the command)
- Look at the new files in your account:
ls -l minilab1_v1.*
-rwx------. 1 231a 231a 1079 Sep 12 09:18 minilab1_v1*
-rw-------. 1 231a 231a 606 Sep 12 09:18 minilab1_v1.asm
-rw-------. 1 231a 231a 2398 Sep 12 09:47 minilab1_v1.lst
-rw-------. 1 231a 231a 1168 Sep 12 09:47 minilab1_v1.o
- Look at the listing generated
1 ;;; minilab1.asm
2 ;;; D. Thiebaut
3 ;;; prints this string on the screen:
4 ;;;
5 ;;; *********************************
6 ;;; * Welcome to CSC231 *
7 ;;; * Home of the Assembly Language *
8 ;;; *********************************
9
10
11 section .data
12
13 00000000 2A2A2A2A2A2A2A2A2A- msg db "*********************************", 10
14 00000009 2A2A2A2A2A2A2A2A2A-
15 00000012 2A2A2A2A2A2A2A2A2A-
16 0000001B 2A2A2A2A2A2A0A
17 00000022 2A2057656C636F6D65- db "* Welcome to CSC231 *", 10
18 0000002B 20746F204353433233-
19 00000034 312020202020202020-
20 0000003D 20202020202A0A
21 00000044 2A20486F6D65206F66- db "* Home of the Assembly Language *", 10
22 0000004D 207468652041737365-
23 00000056 6D626C79204C616E67-
24 0000005F 75616765202A0A
25 00000066 2A2A2A2A2A2A2A2A2A- db "*********************************", 10, 10
26 0000006F 2A2A2A2A2A2A2A2A2A-
27 00000078 2A2A2A2A2A2A2A2A2A-
28 00000081 2A2A2A2A2A2A0A0A
29
30 msgLen equ $-msg
31
32 section .text
33 global _start
34 _start:
35 00000000 B804000000 mov eax,4
36 00000005 BB01000000 mov ebx,1
37 0000000A B9[00000000] mov ecx,msg
38 0000000F BA89000000 mov edx,msgLen
39 00000014 CD80 int 0x80
40
41 ;;; exit
42 00000016 B801000000 mov eax,1
43 0000001B BB00000000 mov ebx,0
44 00000020 CD80 int 0x80
45
46
- Try to recognize all the features. What is code, what is data, what strings like "CD80" mean... (we'll do that in class!)
