CSC231 Homework 4 Solutions 2014
--D. Thiebaut (talk) 16:16, 21 October 2014 (EDT)
Contents
Problem #1
;;; ; -------------------------------------------------------------------
;;; ; hw4a.asm
;;; ; Lei Lei
;;; ;
;;; ; Given the following definition:
;;; ; msg db 3,"ALL",11,"PROGRAMMERS",3,"ARE",11,"PLAYWRIGHTS"
;;; ; db 3,"AND",3,"ALL",9,"COMPUTERS",3,"ARE",5,"LOUSY"
;;; ; db 6,"ACTORS"
;;; ; This program outputs each letter of msg capitalized in a line:
;;; ;
;;; ; All
;;; ; Programmers
;;; ; Are
;;; ; Playwrights
;;; ; And
;;; ; All
;;; ; Computers
;;; ; Are
;;; ; Lousy
;;; ; Actors
;;; ;
;;; ; to assemble and run:
;;; ;
;;; ; nasm -f elf -F stabs hw4a.asm
;;; ; ld -o hw4a hw4a.o
;;; ; ./hw4a
;;; ; -------------------------------------------------------------------
;;; ; -----------------------------------------------------------
;;; ; Constants
;;; ; -----------------------------------------------------------
EXIT equ 1
WRITE equ 4
STDOUT equ 1
;;; ------------------------------------------------------------
;;; data areas
;;; ------------------------------------------------------------
section .data
msg db 3,"ALL",11,"PROGRAMMERS",3,"ARE",11,"PLAYWRIGHTS"
db 3,"AND",3,"ALL",9,"COMPUTERS",3,"ARE",5,"LOUSY"
db 6,"ACTORS"
N equ 10
newLine db 0x0A
line_len equ 1
counter dd 0
temp1 dd 0
temp2 dd 0
;;; ------------------------------------------------------------
;;; code area
;;; ------------------------------------------------------------
section .text
global _start
_start: mov ecx, N
for: push ecx ;Main loop, loop for N=10 times
mov esi, msg
add esi, dword[counter] ;esi points to integer
inc dword[counter]
mov eax, WRITE
mov ebx, STDOUT
mov ecx, msg
add ecx, dword[counter] ;ecx points to first letter
mov edx, 1
int 0x80 ;print first letter in cap
movzx ecx, byte[byte esi] ;move the integer to ecx
dec ecx ;minus the already printed first letter
inc dword[counter]
call printLower
call printLine
pop ecx
loop for
;;; exit()
mov eax,EXIT
mov ebx,0
int 0x80 ; final system call
;;; ----------------------------------------------------------------
;;; printLower: Print letters in lower case
;;; ----------------------------------------------------------------
printLower:
forLower:
push ecx
mov eax, WRITE
mov ebx, STDOUT
mov ecx, msg
add ecx, dword[counter]
add dword[ecx], 'a'-'A' ;change into lower case
mov edx, 1
int 0x80
inc dword[counter]
pop ecx
loop forLower
ret
;;; ---------------------------------------------------------------
;;; printLine: Hard break and print new line
;;; ---------------------------------------------------------------
printLine:
section .bss
.temp resd 1
section .text
mov eax, WRITE
mov ebx, STDOUT
mov edx, line_len
push ecx
lea ecx, [newLine]
int 0x80
pop ecx
ret
Problem 3
;;; ; Hw4_3.asm
;;; ; D. Thiebaut
;;; ;
;;; ; displays the first Fibonacci terms along with a string
;;; ; identifying the terms.
;;; ;
;;; ; Example:
;;; ; Fibonacci(0) =1
;;; ; Fibonacci(1) =1
;;; ; Fibonacci(2) =2
;;; ; Fibonacci(3) =3
;;; ; Fibonacci(4) =5
;;; ; Fibonacci(5) =8
;;; ; ...
;;; ; To assemble and run:
;;; ;
;;; ; nasm -f elf Hw3_5.asm
;;; ; nasm -f elf 231Lib.asm
;;; ; ld -melf_i3896 -o Hw3_5 Hw3_5.o 231Lib.o
;;; ; ./Hw3_5
;;; ; -------------------------------------------------------------------
extern _printDec
;;; ------------------------------------------------------------
;;; data areas
;;; ------------------------------------------------------------
section .data
Fibo db "Fibonacci("
FIBOLEN equ $-Fibo
Equal db ") ="
EQUALLEN equ $-Equal
counter dd 2
temp dd 0 ; holds ecx as loop counter
;;; ------------------------------------------------------------
;;; code area
;;; ------------------------------------------------------------
section .text
global _start
;;; --------------------------------------------------
;;; printLn: prints a new line
;;; --------------------------------------------------
printLn:
section .data
msg1 db 0x0a
section .text
push eax
push ebx
push ecx
push edx
mov eax, 4
mov ebx, 1
mov ecx, msg1
mov edx, 1
int 0x80
pop edx
pop ecx
pop ebx
pop eax
ret
;;; --------------------------------------------------
;;; printMsg: prints the message passed in ecx (address)
;;; and edx (# of chars). Does not modify eax or ebx.
;;; --------------------------------------------------
printMsg: push eax
push ebx
mov eax, 4
mov ebx, 1
int 0x80
pop ebx
pop eax
ret
;;; --------------------------------------------------
;;; printFibMsg: gets a number in eax, and prints it
;;; between parentheses, as in "Fibonacci(###) = "
;;; --------------------------------------------------
printFibMsg: push eax
push ebx
push ecx
push edx
;; print "Fibonacci("
mov ecx, Fibo
mov edx, FIBOLEN
call printMsg
;; print eax
call _printDec
;; print ")="
mov ecx, Equal
mov edx, EQUALLEN
call printMsg
pop edx
pop ecx
pop ebx
pop eax
ret
_start:
;;; display Fibonacci(0) =1
mov eax, 0
call printFibMsg
mov eax, 1
call _printDec
call printLn
;;; display Fibonacci(1) =1
mov eax, 1
call printFibMsg
mov eax, 1
call _printDec
call printLn
;;; start for loop
mov esi, 1 ; esi is Fib[i-1]
mov edi, 1 ; edi is Fib[i-2]
mov ecx, 40-2
for:
push ecx
mov eax, dword[counter]
call printFibMsg
mov eax, esi ; eax <- Fib[i-1]
add eax, edi ; eax <- FIb[i-1]+Fib[i-2]
call _printDec ; print Fib[i]
call printLn
mov edi, esi
mov esi, eax
pop ecx
loop for
;;; exit
mov eax,1
mov ebx,0
int 0x80 ; final system call
