Assembly Progamming Ranger

Multiplication Table Program

2008-11-08T23:03:00.000-08:00

A multiplication table program that accepts up to 10 as n value

Source Code:

jmp start

newLine db 10,13,"$"
space db " $"
cont_mess db 10,13," Do you want to continue (y/n) :$"
msg1 db 10,13," Enter number: $"
mulframe1 db 10,13," ÉÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ»"
db 10,13," º Multiplcation Table º"
db 10,13," ÈÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ¼$"
cnt_num db 0
num1 db 0
num2 db 0
num_final db 0
product db 0
temp1 db 0
temp2 db 0
temp3 db 0

start:

mov ax,3
int 10h
mov product,0
mov num1,0
mov num2,0

lea dx,mulframe1
mov ah,9
int 21h

call new_Line

lea dx,msg1
mov ah,9
int 21h

mov ah,1
int 21h
sub al,30h

mov num1,al

mov ah,1
int 21h
cmp al,13
je execute

sub al,30h
mov num2,al

mov al,num1
mov bl,10

mul bl
mov num1,al

execute:

mov al,num1
mov bl,num2
add al,bl

cmp al,1
jl start
cmp al,10
jg start

mov num_final,al

call clear

call new_Line

mov al,num_final
mov ah,0
mov si,ax

mov cnt_num,1
mov di,0
outerloop:
call new_Line
mov product,0

mov al,num_final
mov ah,0

mov cx,ax

mov al,0
innerloop:
mov al,product
mov bl,cnt_num
add al,bl
mov product,al
mov product,al

call spacer
call spacer
call spacer2
call mul_display

loop innerloop

inc cnt_num
inc di
cmp di,si
jne outerloop

call continue

new_Line:
lea dx,newLine
mov ah,9
int 21h
ret
clear:
xor ax,ax
xor bx,bx
ret

mul_display:
call clear

mov al,product

mov bl,10

div bl
mov temp1,ah
mov temp2,al

call clear
mov bl,10
mov al,temp2

div bl
mov temp3,al
mov temp2,ah

call clear

cmp temp3,0
je tens

mov al,temp3

hundred:

mov dl,al
or dl,30h
mov ah,2
int 21h

tens:

mov al,temp2
mov bl,temp3

add al,bl
cmp al,0
je ones
mov al,temp2

mov dl,al
or dl,30h
mov ah,2
int 21h

ones:
mov al,temp1
mov dl,al
or dl,30h
mov ah,2
int 21h
ret
spacer:
lea dx,space
mov ah,9
int 21h

ret
spacer2:
mov al,product
cmp al,9
jg return

lea dx,space
mov ah,9
int 21h
return:
ret

continue:
call new_Line
xor dx,dx

lea dx,cont_mess
mov ah,9
int 21h

mov ah,1
int 21h

cmp al,'y'
je start_bridge
cmp al,'n'
je con_quit

jmp continue

start_bridge:
call start
con_quit:
int 20h
fullclear:
xor ax,ax
xor bx,bx
xor cx,cx
xor dx,dx
ret

Password Program

2008-11-08T20:19:00.000-08:00

This is a password program i made the password must be pre-declared in the program which is "aces_word" variable and also the user is only allowed to 3 mistakes in typing the right password

source code:

jmp start

mess2 db 10,13," Enter Password: $"
passframe1 db 10,13," ÉÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ»$"
invalid db 10,13," º Invalid password (hit) any key º$"
valid db 10,13," º Valid password º$"
timeout db 10,13," º Time is up! you are allowed 3 tries º$"
passframe2 db 10,13," ÈÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ¼$"
bSpace db 8,"$"
choice db 0
pass_word db 100 dup 0 ;comment: "user input"
aces_word db 'p','o','w','e','r' ;comment: "pre-define password"
aces_cnt dw 5 ;comment: "pre-define number of characters in the password"
word_cnt dw 0
try dw 1 ;comment: "Counts the number of invalid"
newLine db 10,13,"$"
space db " $"
cont_mess db 10,13," Do you want to continue (y/n) :$"

start:
mov try,1
password:
mov ax,3
int 10h

mov word_cnt,0

lea dx,mess2
mov ah,9
int 21h

mov bx,0
input:
mov ah,8
int 21h

cmp al,13
je safety
cmp al,8
je backspace

mov pass_word[bx],al
inc bx

mov dl,'*'
mov ah,2
int 21h

jmp safetyzone

backspace:
cmp bx,0
je input

lea dx,bSpace
mov ah,9
int 21h

mov dl,' '
mov ah,2
int 21h

lea dx,bSpace
mov ah,9
int 21h

dec bx

safetyzone:
jmp input

safety:
mov word_cnt,bx

mov ax,aces_cnt

cmp ax,bx
jne mismatch

mov bx,word_cnt
mov cx,bx
mov bx,0

checking:

mov al,pass_word[bx]
mov ah,aces_word[bx]
cmp al,ah
jne mismatch
inc bx

loop checking
call ok_message
call exit
mismatch:
mov ax,try

cmp ax,3
je timesup

inc try

call error
mov ah,1
int 21h

call password

timesup:
call timesup_message

exit:
call continue

error:
lea dx,passframe1
mov ah,9
int 21h

lea dx,invalid
mov ah,9
int 21h

lea dx,passframe2
mov ah,9
int 21h
ret

ok_message:
lea dx,passframe1
mov ah,9
int 21h

lea dx,valid
mov ah,9
int 21h

lea dx,passframe2
mov ah,9
int 21h
ret

timesup_message:
lea dx,passframe1
mov ah,9
int 21h

lea dx,timeout
mov ah,9
int 21h

lea dx,passframe2
mov ah,9
int 21h
ret

new_Line:
lea dx,newLine
mov ah,9
int 21h
ret
clear:
xor ax,ax
xor bx,bx
ret

spacer:
lea dx,space
mov ah,9
int 21h

ret
continue:
call new_Line
xor dx,dx

lea dx,cont_mess
mov ah,9
int 21h

mov ah,1
int 21h

cmp al,'y'
je start_bridge
cmp al,'n'
je con_quit

jmp continue

start_bridge:
call start
con_quit:
int 20h
fullclear:
xor ax,ax
xor bx,bx
xor cx,cx
xor dx,dx
ret

String Manipulation

2008-11-05T00:00:00.000-08:00

String manipulation in assembly is quite confusing sometimes, when i was making an assembly program for it

this is how you declare a string

string db 12,10 dup 0

In this example a variable string is declared in byte, we want the string to have 10 elements, but in assembly you have to add 2 more elements those we 12 elements in total. The index [0] of the string hold the maximum size of the array which is 10 and index [1] holds that actual size of the string that the user inputed.

in this sample program, we want a user to input a string and displays the string, displays the alphabet characters, numbers, and special characters.

jmp start
string db 100,101 dup 0
mess1 db 10,13," Enter a string: $"
mess2 db 10,13, " Inputted String: $"
alphamess db 10,13, " Alphabet letters: $"
nummess db 10,13, " Numerical Values: $"
charmess db 10,13, " Special characters: $"
contmess db 10,13, " Do you want to continue (y/n): $"
space db " $"
newline db 10,13,"$"
start:
xor ax,ax
xor bx,bx
xor dx,dx
xor cx,cx
xor si,si
xor di,di

mov ax,3
int 10h

call new_Line

lea dx,mess1
mov ah,9
int 21h

lea dx,string
mov ah,10
int 21h
;------------------------displaying string----------------------
call new_Line
lea dx,mess2
mov ah,9
int 21h

lea si,string+1
mov cl,[si]
lea di,string+2
cmp cl,0
je start
display:
mov dl,[di]
mov ah,2
int 21h
inc di
loop display

;------------------------Sorting alpha-----------------------
lea dx,alphamess
mov ah,9
int 21h

lea si,string+1
mov cl,[si]
lea di,string+2

alphasorting:
mov al,[di]
cmp al,65
jl safety

cmp al,122
jg safety
cmp al,91
je safety
cmp al,92
je safety
cmp al,93
je safety
cmp al,95
je safety
cmp al,96
je safety

mov dl,al
mov ah,2
int 21h
call spacer
safety:
inc di
loop alphasorting

;------------------------Sorting Numerical-----------------------
lea dx,nummess
mov ah,9
int 21h

lea si,string+1
mov cl,[si]
lea di,string+2

numsorting:
mov al,[di]

cmp al,48
jl numsafety
cmp al,57
jg numsafety

mov dl,al
mov ah,2
int 21h
call spacer

numsafety:
inc di
loop numsorting

;-----------------------special character sorting-------------------
lea dx,charmess
mov ah,9
int 21h

lea si,string+1
mov cl,[si]
lea di,string+2

charsorting:
mov al,[di]

cmp al,32
je charsafety
cmp al,58
je specialchar
cmp al,59
je specialchar
cmp al,60
je specialchar
cmp al,61
je specialchar
cmp al,62
je specialchar
cmp al,63
je specialchar
cmp al,64
je specialchar
cmp al,91
je specialchar
cmp al,92
je specialchar
cmp al,93
je specialchar
cmp al,94
je specialchar
cmp al,95
je specialchar
cmp al,96
je specialchar
cmp al,58
je specialchar
cmp al,48
jl specialchar
cmp al,122
jle charsafety

specialchar:
mov dl,al
mov ah,2
int 21h
call spacer

charsafety:
inc di
loop charsorting

continue:
call new_Line
xor dx,dx

lea dx,contmess
mov ah,9
int 21h

mov ah,1
int 21h

cmp al,'y'
je start_bridge
cmp al,'n'
je quit

jmp continue
quit:
int 20h
new_Line:
lea dx,newline
mov ah,9
int 21h
spacer:
lea dx,space
mov ah,9
int 21h

ret
start_bridge:
call start

Array Manipulation

2008-11-04T23:12:00.000-08:00

This project is an array manipulation that accepts an array of 15 single digit numbers and arranges it ascending and descending order. Also displays in even- odd and odd-even format

jmp start
mess1 db 10,13," Enter an array of 15 (0-9) : $"
mess2 db 10,13," Array content: $"
mess3 db 10,13," Enter Choice: $"
mess4 db 10,13," Original Array: $"
evenodd db 10,13," Even-odd sequence: $"
oddeven db 10,13," Odd-even sequence: $"
ascend db 10,13," Ascending order: $"
descend db 10,13," Descending order: $"

menu0 db 10,13," €€€€€€€€€€€€€€ menu €€€€€€€€€€€€€$"
twoline db 10,13," €€ €€$"
menu1 db 10,13," €€ (1) Ascending order €€$"
menu2 db 10,13," €€ (2) Descending order €€$"
menu3 db 10,13," €€ (3) Even-odd format €€$"
menu4 db 10,13," €€ (4) Odd-even fomrat €€$"
menu5 db 10,13," €€ (5) Enter new array €€$"
menu6 db 10,13," €€ (6) Quit €€$"
menu7 db 10,13," €€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€$"
cont_mess db 10,13," Do you want to continue (y/n): $"

newline db 10,13,"$"
space db " $"

arrayNum db 15 dup 0
origNum db 15 dup 0
even_num db 15 dup 0
odd_num db 15 dup 0
choice db 0
temp db 0
count_even db 0
count_odd db 0
start:
xor ax,ax
xor bx,bx
xor cx,cx
xor dx,dx

mov arrayNum,0
mov origNum,0
mov even_num,0
mov odd_num,0

mov choice,0
mov temp,0
mov count_even,0
mov count_odd,0

mov ax,3
int 10h

lea dx,mess1
mov ah,9
int 21h

mov bx,0
mov cx,15
mov ah,0

fillArray:

lea dx,space
mov ah,9
int 21h

mov ah,1
int 21h
sub al,30h

cmp al,0
jl start
cmp al,9
jg start

mov arrayNum[bx],al
mov origNum[bx],al

inc bx

loop fillArray

call new_Line
;----------------------------sorting---------------------------
sorter:
call clear
mov di,15
mov ah,0
mov bx,0

outerloop:
mov si,0
mov cx,15
innerloop:
mov al,arrayNum[bx]
mov ah,arrayNum[si]

cmp al,ah
jg skip

mov al,arrayNum[bx]
mov ah,arrayNum[si]

mov temp,al
mov al,ah
mov ah,temp
mov arrayNum[bx],al
mov arrayNum[si],ah

skip:
inc si
loop innerloop

safety:
inc bx
dec di
cmp di,0
jg outerloop
cmp di,0
jl safetyzone

safetyzone:
;-------------------sorting even------------------------
call clear

mov cx,15
mov si,0
mov di,0
sorteven:
xor ax,ax

mov al,arrayNum[si]
xor bx,bx
mov bl,2
div bl

call even_numbers

inc si

loop sorteven

;-------------------------- Sorting odd --------------------------
call clear

mov cx,15
mov si,0
mov di,0
oddsorter:
xor ax,ax

mov al,arrayNum[si]
xor bx,bx
mov bl,2
div bl

call odd_numbers

inc si

loop oddsorter
;------------------------- menu ------------------------------
menu:
mov ax,3
int 10h
;--------------------- shows the original array --------------
lea dx,mess4
mov ah,9
int 21h

mov cx,15
mov bx,0

showArray:

mov dl,origNum[bx]
or dl,30h
mov ah,2
int 21h

lea dx,space
mov ah,9
int 21h

inc bx

loop showArray

;------------------------------ end of show -----------------------
call new_Line

lea dx,menu0
mov ah,9
int 21h

lea dx,twoline
mov ah,9
int 21h

lea dx,menu1
mov ah,9
int 21h

lea dx,menu2
mov ah,9
int 21h

lea dx,menu3
mov ah,9
int 21h

lea dx,menu4
mov ah,9
int 21h

lea dx,menu5
mov ah,9
int 21h

lea dx,menu6
mov ah,9
int 21h

lea dx,twoline
mov ah,9
int 21h

lea dx,menu7
mov ah,9
int 21h

call new_Line

lea dx,mess3
mov ah,9
int 21h

mov ah,1
int 21h
sub al,30h

cmp al,1
jl menu_bridge

cmp al,6
jg menu_bridge

mov choice,al

cmp al,1
je ascend1
cmp al,2
je descend1
cmp al,3
je even_odd1
cmp al,4
je odd_even1
cmp al,5
je new
cmp al,6
je quit
menu_bridge:
call menu
new:
call start
ascend1:
call ascending
descend1:
call descending
even_odd1:
call even_odd
odd_even1:
call odd_even
quit:
int 20h
new_Line:
lea dx,newline
mov ah,9
int 21h
ret
clear:
xor ax,ax
xor bx,bx
xor cx,cx
xor dx,dx
ret
display_array:
lea dx,ascend
mov ah,9
int 21h

mov cx,15
mov bx,0

dispArray:

mov dl,arrayNum[bx]
or dl,30h
mov ah,2
int 21h

lea dx,space
mov ah,9
int 21h

inc bx

loop dispArray
ret
even_numbers:

cmp ah,0
jne odd_counter

mov al,arrayNum[si]
mov even_num[di],al

inc di

inc count_even

jmp return

odd_counter:
inc count_odd
return:
ret
showEven:

call clear

xor ax,ax

mov si,0
mov cl,count_even
cmp cl,0
je evenNumbers
dispEven:

mov dl,even_num[si]
or dl,30h
mov ah,2
int 21h

lea dx,space
mov ah,9
int 21h

inc si
dec cl
cmp cl,0
jg dispEven
cmp cl,0
jl evenNumbers
evenNumbers:
ret

odd_numbers:

cmp ah,0
je oddreturn

mov al,arrayNum[si]
mov odd_num[di],al
inc di
oddreturn:
ret
showOdd:

call clear

xor ax,ax

mov si,0
mov cl,count_odd
cmp cl,0
je oddNumbers

dispOdd:

mov dl,odd_num[si]
or dl,30h
mov ah,2
int 21h

lea dx,space
mov ah,9
int 21h

inc si
dec cl
cmp cl,0
jg dispOdd
cmp cl,0
jl oddNumbers
oddNumbers:
ret

ascending:
call display_array
call continue
descending:
lea dx,descend
mov ah,9
int 21h

mov cx,15
mov bx,14

dispdescend:

mov dl,arrayNum[bx]
or dl,30h
mov ah,2
int 21h

lea dx,space
mov ah,9
int 21h

dec bx

loop dispdescend

call continue
even_odd:
lea dx,evenodd
mov ah,9
int 21h

call showEven
call showOdd
call continue
odd_even:
lea dx,oddeven
mov ah,9
int 21h

call showOdd
call showEven
call continue
continue:
call new_Line
xor dx,dx

lea dx,cont_mess
mov ah,9
int 21h

mov ah,1
int 21h

cmp al,'y'
je start_bridge
cmp al,'n'
je quit2

jmp continue

start_bridge:
call menu
quit2:

int 20h

Array manipulation

2008-11-04T06:07:00.000-08:00

In declaring an array in assembly is quite different from other programming language

eg.

array db 15 dup 0

in this example, a variable array is defined as a byte and has 15 elements in the array. And each element has a default value of 0.

here is a sample program that asks a 15 single-digit numerical input and displays its total, average, also its even and odd numbers.

source code:

jmp start
arrayNum db 15 dup 0
mess1 db 10,13," Input an array of (0 - 9) 15 numbers: $"
mess2 db 10,13," Array content: $"
sum_mess db 10,13," Summation : $"
ave_mess db 10,13," Average : $"
tot_mess db 10,13," Total numbers: "
space db " $"
newline db 10,13,"$"
point db ".$"
even_mess db 10,13," Even numbers: $"
odd_mess db 10,13," Odd numbers: $"
cont_mess db 10,13," Do you want to continue (y/n): $"
even_num db 15 dup 0
odd_num db 15 dup 0

sum db 0
temp1 db 0
temp2 db 0
temp3 db 0
count_even db 0
count_odd db 0
divisor db 0
zero db "0.00$"
start:
xor ax,ax
xor bx,bx
xor cx,cx

mov even_num,0
mov odd_num,0
mov count_even,0
mov count_odd,0

mov ax,3
int 10h

lea dx,mess1
mov ah,9
int 21h

mov bx,0
mov cx,15
mov ah,0

fillArray:

lea dx,space
mov ah,9
int 21h

mov ah,1
int 21h
sub al,30h

cmp al,0
jl start
cmp al,9
jg start

mov arrayNum[bx],al

inc bx

loop fillArray

call new_Line

lea dx,mess2
mov ah,9
int 21h

mov cx,15
mov bx,0

dispArray:

mov dl,arrayNum[bx]
or dl,30h
mov ah,2
int 21h

lea dx,space
mov ah,9
int 21h

inc bx

loop dispArray

;-------------------getting sum of the array---------------

mov bx,0
mov cx,15

mov ah,0

sumArray:

mov al,arrayNum[bx]
add ah,al
inc bx

loop sumArray
mov sum,ah

;------------------------Displaying sum--------------------

lea dx,sum_mess
mov ah,9
int 21h

call sum_display

;-----------------------calculating average-----------------

lea dx,ave_mess
mov ah,9
int 21h

call clear
mov divisor,15
call averaging

;-------------------------sorting array----------------------
call clear

mov cx,15
mov si,0
mov di,0
sorter:
xor ax,ax

mov al,arrayNum[si]
xor bx,bx
mov bl,2
div bl

call even_numbers

inc si

loop sorter

;--------------------- displaying even --------------------
call new_Line
call clear

lea dx,even_mess
mov ah,9
int 21h

call clear

xor ax,ax

mov si,0
mov cl,count_even
dispEven:

mov dl,even_num[si]
or dl,30h
mov ah,2
int 21h

lea dx,space
mov ah,9
int 21h

inc si
dec cl
cmp cl,0
jg dispEven
cmp cl,0
jl evenNumbers
evenNumbers:
;--------------------- displaying numbers of even ----------------
lea dx,tot_mess
mov ah,9
int 21h

mov al,count_even
mov sum,al
call sum_display

summationEven:
;---------------------- calculating sum for even ------------------
call clear
mov al,count_even
mov ah,0

cmp al,0
je safety

mov bx,0
mov cx,ax
mov ah,0

sumEven:

mov al,even_num[bx]
add ah,al
inc bx

loop sumEven
safety:
mov sum,0
mov sum,ah
;------------------------Displaying sum--------------------
call clear

lea dx,sum_mess
mov ah,9
int 21h

call sum_display

;---------------------- average for even ---------------------------
call clear
lea dx,ave_mess
mov ah,9
int 21h

mov al,count_even
cmp al,0
je zero_num

call clear
mov al,count_even
mov divisor,al
call averaging
jmp safetyzone
zero_num:
lea dx,zero
mov ah,9
int 21h
safetyzone:
;---------------------------sorting odd--------------------------
call clear

mov cx,15
mov si,0
mov di,0
oddsorter:
xor ax,ax

mov al,arrayNum[si]
xor bx,bx
mov bl,2
div bl

call odd_numbers

inc si

loop oddsorter
;-------------------- displaying odd ---------------------
call new_Line
call clear

lea dx,odd_mess
mov ah,9
int 21h

call clear

xor ax,ax

mov si,0
mov cl,count_odd
dispOdd:

mov dl,odd_num[si]
or dl,30h
mov ah,2
int 21h

lea dx,space
mov ah,9
int 21h

inc si
dec cl
cmp cl,0
jg dispOdd
cmp cl,0
jl oddNumbers
oddNumbers:
;---------------------display number of odd-------------------
lea dx,tot_mess
mov ah,9
int 21h

mov al,count_odd
mov sum,al
call sum_display
;---------------------- calculating sum for odd ------------------
call clear
mov al,count_odd
mov ah,0

cmp al,0
je oddsafety

mov bx,0
mov cx,ax
mov ah,0

sumOdd:

mov al,odd_num[bx]
add ah,al
inc bx

loop sumOdd
oddsafety:
mov sum,0
mov sum,ah
;------------------------Displaying sum--------------------
call clear

lea dx,sum_mess
mov ah,9
int 21h

call sum_display
;------------------------ averaging for odd --------------------
call clear
lea dx,ave_mess
mov ah,9
int 21h

mov al,count_odd
cmp al,0
je zero_sum

call clear
mov al,count_odd
mov divisor,al
call averaging
jmp oddsafetyzone
zero_sum:
lea dx,zero
mov ah,9
int 21h
oddsafetyzone:

continue:
call new_Line
xor dx,dx

lea dx,cont_mess
mov ah,9
int 21h

mov ah,1
int 21h

cmp al,'y'
je start_bridge
cmp al,'n'
je quit

jmp continue

start_bridge:
call start
quit:
int 20h

even_numbers:

cmp ah,0
jne odd_counter

mov al,arrayNum[si]
mov even_num[di],al

inc di

inc count_even

jmp return

odd_counter:
inc count_odd

return:
ret

odd_numbers:

cmp ah,0
je return

mov al,arrayNum[si]
mov odd_num[di],al
inc di

jmp oddreturn

oddreturn:
ret

new_Line:

lea dx,newline
mov ah,9
int 21h
ret

clear:

xor ax,ax
xor bx,bx
xor cx,cx
xor dx,dx
ret

sum_display:
call clear
mov al,sum

mov bl,10

div bl
mov temp1,ah
mov temp2,al

call clear
mov bl,10
mov al,temp2

div bl
mov temp3,al
mov temp2,ah

call clear

cmp temp3,0
je tens

mov al,temp3

hundred:
mov dl,al
or dl,30h
mov ah,2
int 21h

tens:
mov al,temp2
mov bl,temp3

add al,bl
cmp al,0
je ones

mov al,temp2

mov dl,al
or dl,30h
mov ah,2
int 21h

ones:
mov al,temp1
mov dl,al
or dl,30h
mov ah,2
int 21h
ret

averaging:
call clear
mov al,sum
mov bl,divisor

div bl
mov bh,ah

xor dx,dx
xor cx,cx

mov dl,al
or dl,30h
mov ah,2
int 21h

lea dx,point
mov ah,9
int 21h

mov cx,2
decimal:
mov bl,10
mov al,bh

mul bl
mov bl,divisor
div bl

mov bh,ah
xor dx,dx
mov dl,al
or dl,30h
mov ah,2
int 21h

loop decimal
ret

Displaying asterisk triangles

2008-11-04T04:33:00.000-08:00

Source Code:

jmp start

mess1 db 10,13, "Enter value for (n) [0-9 only]: $"
mess2 db 10,13, "There is nothing to display $"
mess3 db 10,13, "Do you want to continue (y/n): $"
lincar db 10,13, "$"
space db " $"
asterisk db "*$"
value db 0

start:

xor ax,ax
xor bx,bx
xor cx,cx

mov ax,3
int 10h

lea dx,mess1
mov ah,9
int 21h

mov ah,1
int 21h
sub al,30h

cmp al,0
je zero
cmp al,0
jl start
cmp al,9
jg start

mov value,al
mov bh,al
mov ch,bh
mov cl,al
again:

cmp bh,0
je continue

lea dx,lincar
mov ah,9
int 21h

mov al,value
sub cl,al
back:

cmp cl,0
je display

lea dx,space
mov ah,9
int 21h

inc cl

jmp back

display:

lea dx,asterisk
mov ah,9
int 21h

lea dx,space
mov ah,9
int 21h

inc cl

cmp cl,ch
jne display

dec bh
dec ch
dec cl

jmp again
zero:
lea dx,mess2
mov ah,9
int 21h

continue:
xor dx,dx

lea dx,mess3
mov ah,9
int 21h

mov ah,1
int 21h

cmp al,'y'
je start_bridge
cmp al,'n'
je exit

jmp continue

start_bridge:
call start

exit:
int 20h

Displaying asterisk triangles

2008-11-04T03:39:00.000-08:00

This one is shape like a quadrilateral triangle

Source Code:

jmp start

mess1 db 10,13, "Enter value for (n) [0-9 only]: $"
mess2 db 10,13, "There is nothing to display $"
mess3 db 10,13, "Do you want to continue (y/n): $"
lincar db 10,13, "$"
space db " $"
asterisk db "*$"
value db 0

start:

xor ax,ax
xor bx,bx
xor cx,cx

mov ax,3
int 10h

lea dx,mess1
mov ah,9
int 21h

mov ah,1
int 21h
sub al,30h

cmp al,0
je zero
cmp al,0
jl start
cmp al,9
jg start

mov bh,al
mov value,al

mov ch,1

again:

cmp bh,0
je continue

lea dx,lincar
mov ah,9
int 21h

mov bl,value
mov al,ch

sub al,bl

mov cl,al

back:

cmp cl,0
je display

lea dx,space
mov ah,9
int 21h

inc cl

jmp back
display:

lea dx,asterisk
mov ah,9
int 21h

lea dx,space
mov ah,9
int 21h

inc cl

cmp cl,ch
jne display

dec bh
inc ch

jmp again
zero:
lea dx,mess2
mov ah,9
int 21h

continue:
xor dx,dx

lea dx,mess3
mov ah,9
int 21h

mov ah,1
int 21h

cmp al,'y'
je start_bridge
cmp al,'n'
je exit

jmp continue

start_bridge:
call start

exit:
int 20h

Displaying asterisk triangles

2008-11-04T03:12:00.000-08:00

Another version with two triangles connected at one point

Source Code:

jmp start
mess1 db 10,13, "Enter a value [0-9 only]: $"
mess2 db 10,13, "There is nothing to display $"
mess3 db 10,13, "Do you want to continue (y/n): $"
space db " $"
lincar db 10,13, "$"
value db 0
counter db 0

start:
xor ax,ax
xor bx,bx
xor cx,cx

mov ax,3
int 10h

lea dx,mess1
mov ah,9
int 21h

mov ah,1
int 21h
sub al,30h

cmp al,0
je zero_bridge
cmp al,0
jl start
cmp al,9
jg start

mov value,al

lea dx,lincar
mov ah,9
int 21h

mov ah,0
mov al,value

mov cx,ax
mov counter,1
mov bh,counter
mov bl,1
jmp display
zero_bridge:
call zero
display:
cmp bh,bl
jg next

mov dl,'*'
mov ah,2
int 21h

lea dx,space
mov ah,9
int 21h

inc bh
jmp display

next:
inc bl
mov bh,counter

lea dx,lincar
mov ah,9
int 21h

loop display

;-----------------------------------second half-------------------------------------

mov al,value
sub al,1
cmp al,0
je continue
mov ah,0

mov cx,ax
mov counter,1
mov bh,counter
mov bl,al
mov al,0

display2:
cmp bh,bl
jg next2

mov dl,'*'
mov ah,2
int 21h

lea dx,space
mov ah,9
int 21h

inc bh
jmp display2

next2:
dec bl
inc al
mov bh,counter

lea dx,lincar
mov ah,9
int 21h

loop display2
jmp continue
zero:
lea dx, mess2
mov ah,9
int 21h
continue:
xor dx,dx

lea dx,mess3
mov ah,9
int 21h

mov ah,1
int 21h

cmp al,'y'
je start_bridge
cmp al,'n'
je quit

jmp continue

start_bridge:
call start

quit:
int 20h

Displaying asterisk triangles

2008-11-04T01:05:00.000-08:00

This program displays to right triangles that are connected at one point. It uses a looping principle like the other asterisk triangle .
Source Code:

jmp start

mess1 db 10,13, "Enter value for (n) [0-9 only]: $"
mess2 db 10,13, "There is nothing to display $"
mess3 db 10,13, "Do you want to continue (y/n): $"
lincar db 10,13, "$"
space db " $"
asterisk db "*$"
value db 0

start:

xor ax,ax
xor bx,bx
xor cx,cx

mov ax,3
int 10h

lea dx,mess1
mov ah,9
int 21h

mov ah,1
int 21h
sub al,30h

cmp al,0
je zero_bridge
cmp al,0
jl start
cmp al,9
jg start
jmp main

zero_bridge:
call zero
main:
mov value,al
mov bh,al
mov ch,bh
mov cl,al
again:

cmp bh,0
je secondhalf

lea dx,lincar
mov ah,9
int 21h

mov al,value
sub cl,al
back:

cmp cl,0
je display

lea dx,space
mov ah,9
int 21h

lea dx,space
mov ah,9
int 21h

inc cl

jmp back

display:

lea dx,asterisk
mov ah,9
int 21h

lea dx,space
mov ah,9
int 21h

inc cl

cmp cl,ch
jne display

dec bh
dec ch
dec cl

jmp again

;----------------------------socondhalf----------------------------

secondhalf:

mov al,value
sub al,1
mov bh,al
mov ch,2

again2:

cmp bh,0
je continue

lea dx,lincar
mov ah,9
int 21h

mov bl,value
mov al,ch

sub al,bl

mov cl,al

back2:

cmp cl,0
je display2

lea dx,space
mov ah,9
int 21h

lea dx,space
mov ah,9
int 21h

inc cl

jmp back2
display2:

lea dx,asterisk
mov ah,9
int 21h

lea dx,space
mov ah,9
int 21h

inc cl

cmp cl,ch
jne display2

dec bh
inc ch

jmp again2
zero:
lea dx,mess2
mov ah,9
int 21h
continue:
xor dx,dx

lea dx,mess3
mov ah,9
int 21h

mov ah,1
int 21h

cmp al,'y'
je start_bridge
cmp al,'n'
je exit

jmp continue

start_bridge:
call start
exit:
int 20h

Displaying asterisk triangles

2008-11-03T23:40:00.000-08:00

The Fourth of the set
Source Code:

jmp start

mess1 db 10,13, "Enter value for (n) [0-9 only]: $"
mess2 db 10,13, "There is nothing to display $"
mess3 db 10,13, "Do you want to continue (y/n): $"
lincar db 10,13, "$"
space db " $"
asterisk db "*$"
value db 0

start:

xor ax,ax
xor bx,bx
xor cx,cx

mov ax,3
int 10h

lea dx,mess1
mov ah,9
int 21h

mov ah,1
int 21h
sub al,30h

cmp al,0
je zero
cmp al,0
jl start
cmp al,9
jg start

mov bh,al
mov value,al

mov ch,1

again:

cmp bh,0
je continue

lea dx,lincar
mov ah,9
int 21h

mov bl,value
mov al,ch

sub al,bl

mov cl,al

back:

cmp cl,0
je display

lea dx,space
mov ah,9
int 21h

lea dx,space
mov ah,9
int 21h

inc cl

jmp back
display:

lea dx,asterisk
mov ah,9
int 21h

lea dx,space
mov ah,9
int 21h

inc cl

cmp cl,ch
jne display

dec bh
inc ch

jmp again
zero:
lea dx,mess2
mov ah,9
int 21h
continue:
xor dx,dx

lea dx,mess3
mov ah,9
int 21h

mov ah,1
int 21h

cmp al,'y'
je start_bridge
cmp al,'n'
je exit

jmp continue

start_bridge:
call start
exit:
int 20h

Displaying asterisk triangles

2008-11-03T23:33:00.000-08:00

The third asterisk pattern

Source Code:

jmp start

mess1 db 10,13, "Enter value for (n) [0-9 only]: $"
mess2 db 10,13, "There is nothing to display $"
mess3 db 10,13, "Do you want to continue (y/n): $"
lincar db 10,13, "$"
space db " $"
asterisk db "*$"
value db 0

start:

xor ax,ax
xor bx,bx
xor cx,cx

mov ax,3
int 10h

lea dx,mess1
mov ah,9
int 21h

mov ah,1
int 21h
sub al,30h

cmp al,0
je zero
cmp al,0
jl start
cmp al,9
jg start

mov value,al
mov bh,al
mov ch,bh
mov cl,al
again:
cmp bh,0
je continue

lea dx,lincar
mov ah,9
int 21h

mov al,value
sub cl,al
back:

cmp cl,0
je display

lea dx,space
mov ah,9
int 21h

lea dx,space
mov ah,9
int 21h

inc cl

jmp back

display:

lea dx,asterisk
mov ah,9
int 21h

lea dx,space
mov ah,9
int 21h

inc cl

cmp cl,ch
jne display

dec bh
dec ch
dec cl

jmp again
zero:
lea dx,mess2
mov ah,9
int 21h
continue:
xor dx,dx

lea dx,mess3
mov ah,9
int 21h

mov ah,1
int 21h

cmp al,'y'
je start_bridge
cmp al,'n'
je exit

jmp continue

start_bridge:
call start
exit:
int 20h

Displaying asterisk triangles

2008-11-03T22:26:00.000-08:00

This is the inverted of the last one so here goes nothing

Source Code:

jmp start
mess1 db 10,13, "Enter a value (n) [0-9 only]: $"
mess2 db 10,13, "Do you want to continue (y/n): $"
mess3 db 10,13, "There is nothing to display $"
space db " $"
lincar db 10,13, "$"
value db 0
counter db 0
s_counter db 0

start:
xor ax,ax
xor bx,bx
xor cx,cx

mov ax,3
int 10h

lea dx,mess1
mov ah,9
int 21h

mov ah,1
int 21h
sub al,30h

cmp al,0
jl start
cmp al,9
jg start

mov value,al
cmp al,0
je zero

lea dx,lincar
mov ah,9
int 21h

mov ah,0
mov al,value

mov cx,ax
mov counter,1
mov bh,counter
mov bl,value
mov al,0
display:
cmp bh,bl
jg next

mov dl,'*'
mov ah,2
int 21h

lea dx,space
mov ah,9
int 21h

inc bh
jmp display

next:
dec bl
inc al
mov bh,counter

lea dx,lincar
mov ah,9
int 21h

loop display
jmp quit
zero:
lea dx, mess3
mov ah,9
int 21h
quit:
int 20h

Displaying asterisk triangles

2008-11-03T22:11:00.000-08:00

Will it took me time to get myself to blogging again , this is one my own projects that I program using assembly in my school , but this is just one pattern I'll blog the rest after this

Source Code:

jmp start
mess1 db 10,13, "Enter a value (n) [0-9 only]: $"
mess2 db 10,13, "Do you want to continue (y/n): $"
mess3 db 10,13, "There is nothing to display $"
space db " $"
lincar db 10,13, "$"
value db 0
counter db 0

start:
xor ax,ax
xor bx,bx
xor cx,cx

mov ax,3
int 10h

lea dx,mess1
mov ah,9
int 21h

mov ah,1
int 21h
sub al,30h

cmp al,0
jl start
cmp al,9
jg start

mov value,al
cmp al,0
je zero

lea dx,lincar
mov ah,9
int 21h

mov ah,0
mov al,value

mov cx,ax
mov counter,1
mov bh,counter
mov bl,1
jmp display
start_bridge:
jmp start
display:
cmp bh,bl
jg next

mov dl,'*'
mov ah,2
int 21h

lea dx,space
mov ah,9
int 21h

inc bh
jmp display
next:
inc bl
mov bh,counter

lea dx,lincar
mov ah,9
int 21h

loop display
jmp continue
zero:
lea dx, mess3
mov ah,9
int 21h
jmp continue
continue:
xor dx,dx

lea dx,mess2
mov ah,9
int 21h

mov ah,1
int 21h

cmp al,'y'
je start_bridge
cmp al,'n'
je quit

jmp continue
quit:
int 20h

Gets the sum of two single digit numbers in assembly

2008-10-24T01:42:00.000-07:00

This is a program that calculates the sum of two numbers that are single digit using assembly language.

jmp start
mess1 db 10,13,"Enter 1st value: $"
mess2 db 10,13,"Enter 2nd value: $"
mess3 db 10,13,"Total sum value: $"
mess4 db 10,13,"Do you want ot continue (y/n): $"
sum db 0
start:
mov ax,3
int 10h

lea dx,mess1
mov ah,9
int 21h

mov ah,1
int 21h
sub al,30h

cmp al,0
jl start
cmp al,9
jg start

mov bl,al

lea dx,mess2
mov ah,9
int 21h

mov ah,1
int 21h
sub al,30h

cmp al,0
jl start
cmp al,9
jg start

add al,bl ; adds the two numbers
mov sum,al

lea dx,mess3
mov ah,9
int 21h
cmp al,9
mov al,sum
cmp al,9
jg twodigit
mov dl,al
or dl,30h
mov ah,2
int 21h
jmp continue
int 20h

continue:
xor dx,dx
lea dx,mess4
mov ah,9
int 21h

mov ah,1
int 21h

cmp al,'y'
je start
cmp al,'n'
je quit

twodigit: ; prints sum if above 9
xor ax,ax
mov al,sum
mov bl,10
div bl
mov bh,ah
mov dl,al
or dl,30h
mov ah,2
int 21h
mov dl,bh
or dl,30h
mov ah,2
int 21h
jmp continue

quit:
int 20h

hello world program using assembly language

2008-10-23T21:28:00.000-07:00

Now this is the famous problem in programming that has been pass down from generation too generation how to print the message "hello world!" in the computer screen.

source code:

jmp start

message1 db "Hello world!$"

start:

; clear the screens
mov ax,3
int 10h

; prints the hello world
lea dx,message1
mov ah,9
int 21h

;terminates the program
int 20h

Key Concepts

2008-10-23T20:29:00.000-07:00

Key concepts

Assembler

Typically a modern assembler creates object code by translating assembly instruction mnemonics into opcodes, and by resolving symbolic names for memory locations and other entities.[1] The use of symbolic references is a key feature of assemblers, saving tedious calculations and manual address updates after program modifications. Most assemblers also include macro facilities for performing textual substitution—e.g., to generate common short sequences of instructions to run inline, instead of in a subroutine.

Assemblers are generally simpler to write than compilers for high-level languages, and have been available since the 1950s. Modern assemblers, especially for RISC based architectures, such as MIPS, Sun SPARC and HP PA-RISC, optimize instruction scheduling to exploit the CPU pipeline efficiently.

More sophisticated high-level assemblers provide language abstractions such as:

* Advanced control structures

* High-level procedure/function declarations and invocations

* High-level abstract data types, including structures/records, unions, classes, and sets

* Sophisticated macro processing

* Object-Oriented features such as encapsulation, polymorphism, inheritance, interfaces

See Language design below for more details.

Note that, in normal professional usage, the term assembler is often used ambiguously: It is frequently used to refer to an assembly language itself, rather than to the assembler utility. Thus: "CP/CMS was written in S/360 assembler" as opposed to "ASM-H was a widely-used S/370 assembler."

Assembly language

A program written in assembly language consists of a series of instructions--mnemonics that correspond to a stream of executable instructions, when translated by an assembler, that can be loaded into memory and executed.

For example, an x86/IA-32 processor can execute the following binary instruction as expressed in machine language (see x86 assembly language):

* Binary: 10110000 01100001 (Hexadecimal: B0 61)

The equivalent assembly language representation is easier to remember (example in Intel syntax, more mnemonic):

* MOV AL, 61h

This instruction means:

* Move the value 61h (or 97 decimal; the h-suffix means hexadecimal) into the processor register named "AL".

The mnemonic "mov" represents the opcode 1011 which moves the value in the second operand into the register indicated by the first operand. The mnemonic was chosen by the instruction set designer to abbreviate "move", making it easier for the programmer to remember. A comma-separated list of arguments or parameters follows the opcode; this is a typical assembly language statement.

In practice many programmers drop the word mnemonic and, technically incorrectly, call "mov" an opcode. When they do this they are referring to the underlying binary code which it represents. To put it another way, a mnemonic such as "mov" is not an opcode, but as it symbolizes an opcode, one might refer to "the opcode mov" for example when one intends to refer to the binary opcode it symbolizes rather than to the symbol--the mnemonic--itself. As few modern programmers have need to be mindful of actually what binary patterns are the opcodes for specific instructions, the distinction has in practice become a bit blurred among programmers but not among processor designers.

Transforming assembly into machine language is accomplished by an assembler, and the reverse by a disassembler. Unlike in high-level languages, there is usually a one-to-one correspondence between simple assembly statements and machine language instructions. However, in some cases, an assembler may provide pseudoinstructions which expand into several machine language instructions to provide commonly needed functionality. For example, for a machine that lacks a "branch if greater or equal" instruction, an assembler may provide a pseudoinstruction that expands to the machine's "set if less than" and "branch if zero (on the result of the set instruction)". Most full-featured assemblers also provide a rich macro language (discussed below) which is used by vendors and programmers to generate more complex code and data sequences.

Each computer architecture and processor architecture has its own machine language. On this level, each instruction is simple enough to be executed using a relatively small number of electronic circuits. Computers differ by the number and type of operations they support. For example, a new 64-bit machine would have different circuitry from a 32-bit machine. They may also have different sizes and numbers of registers, and different representations of data types in storage. While most general-purpose computers are able to carry out essentially the same functionality, the ways they do so differ; the corresponding assembly languages reflect these differences.

Multiple sets of mnemonics or assembly-language syntax may exist for a single instruction set, typically instantiated in different assembler programs. In these cases, the most popular one is usually that supplied by the manufacturer and used in its documentation.

Language design

Basic elements

Instructions (statements) in assembly language are generally very simple, unlike those in high-level languages. Each instruction typically consists of an operation or opcode plus zero or more operands. Most instructions refer to a single value, or a pair of values. Generally, an opcode is a symbolic name for a single executable machine language instruction. Operands can be either immediate (typically one byte values, coded in the instruction itself) or the addresses of data located elsewhere in storage. This is determined by the underlying processor architecture: the assembler merely reflects how this architecture works.

Most modern assemblers also support pseudo-operations, which are directives obeyed by the assembler at assembly time instead of the CPU at run time. (For example, pseudo-ops would be used to reserve storage areas and optionally set their initial contents.) The names of pseudo-ops often start with a dot to distinguish them from machine instructions.

Some assemblers also support pseudo-instructions, which generate two or more machine instructions.

Symbolic assemblers allow programmers to associate arbitrary names (labels or symbols) with memory locations. Usually, every constant and variable is given a name so instructions can reference those locations by name, thus promoting self-documenting code. In executable code, the name of each subroutine is associated with its entry point, so any calls to a subroutine can use its name. Inside subroutines, GOTO destinations are given labels. Some assemblers support local symbols which are lexically distinct from normal symbols (e.g., the use of "10$" as a GOTO destination).

Most assemblers provide flexible symbol management, allowing programmers to manage different namespaces, automatically calculate offsets within data structures, and assign labels that refer to literal values or the result of simple computations performed by the assembler. Labels can also be used to initialize constants and variables with relocatable addresses.

Assembly languages, like most other computer languages, allow comments to be added to assembly source code that are ignored by the assembler. Good use of comments is even more important with assembly code than with higher-level languages, as the meaning of a sequence of instructions is harder to decipher from the code itself.

Wise use of these facilities can greatly simplify the problems of coding and maintaining low-level code. Raw assembly source code as generated by compilers or disassemblers — code without any comments, meaningful symbols, or data definitions — is quite difficult to read when changes must be made.

Macros

Many assemblers support macros, programmer-defined symbols that stand for some sequence of text lines. This sequence of text lines may include a sequence of instructions, or a sequence of data storage pseudo-ops. Once a macro has been defined using the appropriate pseudo-op, its name may be used in place of an mnemonic. When the assembler processes such a statement, it replaces the statement with the text lines associated with that macro, then processes them just as though they had appeared in the source code file all along (including, in better assemblers, expansion of any macros appearing in the replacement text).

Since macros can have 'short' names but expand to several or indeed many lines of code, they can be used to make assembly language programs appear to be much shorter (require less lines of source code from the application programmer - as with a higher level language). They can also be used to add higher levels of structure to assembly programs, optionally introduce embedded de-bugging code via parameters and other similar features.

Many assemblers have built-in macros for system calls and other special code sequences.

Macro assemblers often allow macros to take parameters. Some assemblers include quite sophisticated macro languages, incorporating such high-level language elements as optional parameters, symbolic variables, conditionals, string manipulation, and arithmetic operations, all usable during the execution of a given macros, and allowing macros to save context or exchange information. Thus a macro might generate a large number of assembly language instructions or data definitions, based on the macro arguments. This could be used to generate record-style data structures or "unrolled" loops, for example, or could generate entire algorithms based on complex parameters. An organization using assembly language that has been heavily extended using such a macro suite can be considered to be working in a higher-level language, since such programmers are not working with a computer's lowest-level conceptual elements.

Macros were used to customize large scale software systems for specific customers in the mainframe era and were also used by customer personnel to satisfy their employers' needs by making specific versions of manufacturer operating systems; this was done, for example, by systems programmers working with IBM's Conversational Monitor System/Virtual Machine (CMS/VM) and with IBM's "real time transaction processing" add-on, Customer Information Control System, CICS.

It was also possible to use solely the macro processing capabilities of an assembler to generate code written in completely different languages, for example, to generate a version of a program in Cobol using a pure macro assembler program containing lines of Cobol code inside assembly time operators instructing the assembler to generate arbitrary code.

This was because, as was realized in the 1970s, the concept of "macro processing" is independent of the concept of "assembly", the former being in modern terms more word processing, text processing, than generating object code. The concept of macro processing in fact appeared in and appears in the C programming language, which supports "preprocessor instructions" to set variables, and make conditional tests on their values. Note that unlike certain previous macro processors inside assemblers, the C preprocessor was not Turing-complete because it lacked the ability to either loop or "go to", the latter allowing the programmer to loop.

Despite the power of macro processing, it fell into disuse in high level languages while remaining a perennial for assemblers.

This was because many programmers were rather confused by macro parameter substitution and did not disambiguate macro processing from assembly and execution.

Macro parameter substitution is strictly by name: at macro processing time, the value of a parameter is textually substituted for its name. The most famous class of bugs resulting was the use of a parameter that itself was an expression and not a simple name when the macro writer expected a name. In the macro: foo: macro a load a*b the intention was that the caller would provide the name of a variable, and the "global" variable or constant b would be used to multiply "a". If foo is called with the parameter a-c, an unexpected macro expansion occurs.

To avoid this, users of macro processors learned to religiously parenthesize formal parameters inside macro definitions, and callers had to do the same to their "actual" parameters.

PL/I and C feature macros, but this facility was underused or dangerous when used because they can only manipulate text. On the other hand, homoiconic languages, such as Lisp, Prolog, and Forth, retain the power of assembly language macros because they are able to manipulate their own code as data.

Support for structured programming

Some assemblers have incorporated structured programming elements to encode execution flow. The earliest example of this approach was in the Concept-14 macro set developed by Marvin Zloof at IBM's Thomas Watson Research Center, which extended the S/370 macro assembler with IF/ELSE/ENDIF and similar control flow blocks. This was a way to reduce or eliminate the use of GOTO operations in assembly code, one of the main factors causing spaghetti code in assembly language. This approach was widely accepted in the early 80s (the latter days of large-scale assembly language use).

A curious design was A-natural, a "stream-oriented" assembler for 8080/Z80 processors from Whitesmiths Ltd. (developers of the Unix-like Idris operating system, and what was reported to be the first commercial C compiler). The language was classified as an assembler, because it worked with raw machine elements such as opcodes, registers, and memory references; but it incorporated an expression syntax to indicate execution order. Parentheses and other special symbols, along with block-oriented structured programming constructs, controlled the sequence of the generated instructions. A-natural was built as the object language of a C compiler, rather than for hand-coding, but its logical syntax won some fans.

There has been little apparent demand for more sophisticated assemblers since the decline of large-scale assembly language development.[2] In spite of that, they are still being developed and applied in cases where resource constraints or peculiarities in the target system's architecture prevent the effective use of higher-level languages.[3]

Use of assembly language

Historical perspective

Historically, a large number of programs have been written entirely in assembly language. Operating systems were almost exclusively written in assembly language until the widespread acceptance of C in the 1970s and early 1980s. Many commercial applications were written in assembly language as well, including a large amount of the IBM mainframe software written by large corporations. COBOL and FORTRAN eventually displaced much of this work, although a number of large organizations retained assembly-language application infrastructures well into the 90s.

Most early microcomputers relied on hand-coded assembly language, including most operating systems and large applications. This was because these systems had severe resource constraints, imposed idiosyncratic memory and display architectures, and provided limited, buggy system services. Perhaps more important was the lack of first-class high-level language compilers suitable for microcomputer use. A psychological factor may have also played a role: the first generation of microcomputer programmers retained a hobbyist, "wires and pliers" attitude.

In a more commercial context, the biggest reasons for using assembly language were size, speed, and reliability: the writers of Cardbox-Plus said simply "we use assembler because then all the bugs are ours". This held true for 8-bit versions of the program, which had no bugs at all, but ironically it turned out to be false with 16 bits: Cardbox-Plus 2.0 had to be upgraded to Cardbox-Plus 2.1 because a bug in Microsoft's macro assembler caused Cardbox-Plus to index the number "-0" differently from the number "0".[citation needed]

Typical examples of large assembly language programs from this time are the MS-DOS operating system, the early IBM PC spreadsheet program Lotus 1-2-3, and almost all popular games for the Atari 800 family of home computers. Even into the 1990s, most console video games were written in assembly, including most games for the Mega Drive/Genesis and the Super Nintendo Entertainment System[citation needed]. According to some industry insiders, the assembly language was the best computer language to use to get the best performance out the Sega Saturn, a console that was notoriously challenging to develop and program games for [4]. The popular arcade game NBA Jam (1993) is another example. On the Commodore 64, Amiga, Atari ST, as well as ZX Spectrum home computers, assembler has long been the primary development language. This was in large part due to the fact that BASIC dialects on these systems offered insufficient execution speed, as well as insufficient facilities to take full advantage of the available hardware on these systems. Some systems, most notably Amiga, even have IDEs with highly advanced debugging and macro facilities, such as the freeware ASM-One assembler, comparable to that of Microsoft Visual Studio facilities (ASM-One predates Microsoft Visual Studio).

The Assembler for the VIC-20 was written by Don French and published by French Silk. At 1639 bytes in length, its author believes it is the smallest symbolic assembler ever written. The assembler supported the usual symbolic addressing and the definition of character strings or hex strings. It also allowed address expressions which could be combined with addition, subtraction, multiplication, division, logical AND, logical OR, and exponentiation operators.

Current usage

There have always been debates over the usefulness and performance of assembly language relative to high-level languages, though this gets less attention today[citation needed]. Assembly language has specific niche uses where it is important; see below. But in general, modern optimizing compilers are claimed to render high-level languages into code that can run as fast as hand-written assembly, despite some counter-examples that can be created. The complexity of modern processors makes effective hand-optimization increasingly difficult.[6] Moreover, and to the dismay of efficiency lovers, increasing processor performance has meant that most CPUs sit idle most of the time, with delays caused by predictable bottlenecks such as I/O operations and paging. This has made raw code execution speed a non-issue for most programmers.

There are really only a handful of situations where today's expert practitioners would choose assembly language[citation needed]:

* When a stand-alone binary executable is required, i.e. one that must execute without recourse to the run-time components or libraries associated with a high-level language; this is perhaps the most common situation. These are embedded programs that store only a small amount of memory and the device is intended to do single purpose tasks. Such examples consist of telephones, automobile fuel and ignition systems, air-conditioning control systems, security systems, and sensors.

* When interacting directly with the hardware, for example in device drivers.

* When using processor-specific instructions not exploited by or available to the compiler. A common example is the bitwise rotation instruction at the core of many encryption algorithms.

* Embedded systems.

* When extreme optimization is required, e.g., in an inner loop in a processor-intensive algorithm. Some game programmers are experts at writing code that takes advantage of the capabilities of hardware features in systems enabling the games to run faster.

* When a system with severe resource constraints (e.g., an embedded system) must be hand-coded to maximize the use of limited resources; but this is becoming less common as processor price/performance improves

* When no high-level language exists, e.g., on a new or specialized processor

* Real-time programs that need precise timing and responses, such as simulations, flight navigation systems, and medical equipment. (For example, in a fly-by-wire system, telemetry must be interpreted and acted upon within strict time constraints. Such systems must eliminate sources of unpredictable delays – such as may be created by interpreted languages, automatic garbage collection, paging operations, or preemptive multitasking. Some higher-level languages incorporate run-time components and operating system interfaces that can introduce such delays. Choosing assembly or lower-level languages for such systems gives the programmer greater visibility and control over processing details.)

* When complete control over the environment is required (for example in extremely high security situations, where nothing can be taken for granted).

* When writing computer viruses, bootloaders, certain device drivers, or other items very close to the hardware or low-level operating system.

* When reverse-engineering existing binaries, which may or may not have originally been written in a high-level language, for example when cracking copy protection of proprietary software.

* Reverse engineering and modification of video games (known as ROM Hacking), commonly done to games for Nintendo hardware such as the SNES and NES, is possible with a range of techniques, of which the most widely employed is altering the program code at the assembly language level.

* Assembly language is still used for writing games and other software for graphing calculators.[7]

* Finally, compiler writers usually write software that generates assembly code, and should therefore be expert assembly language programmers themselves.

Nevertheless, assembly language is still taught in most Computer Science and Electronic Engineering programs. Although few programmers today regularly work with assembly language as a tool, the underlying concepts remain very important. Such fundamental topics as binary arithmetic, memory allocation, stack processing, character set encoding, interrupt processing, and compiler design would be hard to study in detail without a grasp of how a computer operates at the hardware level. Since a computer's behavior is fundamentally defined by its instruction set, the logical way to learn such concepts is to study an assembly language. Most modern computers have similar instruction sets. Therefore, studying a single assembly language is sufficient to learn: i) The basic concepts; ii) To recognize situations where the use of assembly language might be appropriate; and iii) To see how efficient executable code can be created from high-level languages.

Typical applications

Hard-coded assembly language is typically used in a system's boot ROM (BIOS on IBM-compatible PC systems). This low-level code is used, among other things, to initialize and test the system hardware prior to booting the OS, and is stored in ROM. Once a certain level of hardware initialization has taken place, execution transfers to other code, typically written in higher level languages; but the code running immediately after power is applied is usually written in assembly language. The same is true of most boot loaders.

Many compilers render high-level languages into assembly first before fully compiling, allowing the assembly code to be viewed for debugging and optimization purposes. Relatively low-level languages, such as C, often provide special syntax to embed assembly language directly in the source code. Programs using such facilities, such as the Linux kernel, can then construct abstractions utilizing different assembly language on each hardware platform. The system's portable code can then utilize these processor-specific components through a uniform interface.

Assembly language is also valuable in reverse engineering, since many programs are distributed only in machine code form, and machine code is usually easy to translate into assembly language and carefully examine in this form, but very difficult to translate into a higher-level language. Tools such as the Interactive Disassembler make extensive use of disassembly for such a purpose.

A particular niche that makes use of assembly language is the demoscene. Certain competitions require the contestants to restrict their creations to a very small size (e.g. 256B, 1KB, 4KB or 64 KB), and assembly language is the language of choice to achieve this goal.[9] When resources, particularly CPU-processing constrained systems, like the Amiga and the Commodore 64, are a concern, assembler coding is a must: optimized assembler code is written "by hand" and instructions are sequenced manually by the coders in an attempt to minimize the number of CPU cycles used; the CPU constraints are so great that every CPU cycle counts. However, using such techniques has enabled systems like the Commodore 64 to produce real-time 3D graphics with advanced effects, a feat which might be considered unlikely or even impossible for a system with a 0.99MHz processor.

Related terminology

* Assembly language or assembler language is commonly called assembly, assembler, ASM, or symbolic machine code. A generation of IBM mainframe programmers called it BAL for Basic Assembly Language.

Note: Calling the language assembler is of course potentially confusing and ambiguous, since this is also the name of the utility program that translates assembly language statements into machine code. Some may regard this as imprecision or error. However, this usage has been common among professionals and in the literature for decades.Similarly, some early computers called their assembler its assembly program.)

* The computational step where an assembler is run, including all macro processing, is known as assembly time.

* The use of the word assembly dates from the early years of computers (cf. short code, speedcode).

* A cross assembler (see cross compiler) produces code using one type of processor, which runs on a different type of processor. This technology is particularly important when developing software for new processors, or when developing for embedded systems. This allows, for instance, a 32-bit x86 processor to assemble code to run on a 64-bit x64 processor.

* An assembler directive is a command given to an assembler. These directives may do anything from telling the assembler to include other source files, to telling it to allocate memory for constant data.

Further details

For any given personal computer, mainframe, embedded system, and game console, both past and present, at least one--possibly dozens--of assemblers have been written. For some examples, see the list of assemblers.

On Unix systems, the assembler is traditionally called as, although it is not a single body of code, being typically written anew for each port. A number of Unix variants use GAS.

Within processor groups, each assembler has its own dialect. Sometimes, some assemblers can read another assembler's dialect, for example, TASM can read old MASM code, but not the reverse. FASM and NASM have similar syntax, but each support different macros that could make them difficult to translate to each other. The basics are all the same, but the advanced features will differ.[12]

Also, assembly can sometimes be portable across different operating systems on the same type of CPU. Calling conventions between operating systems often differ slightly or not at all, and with care it is possible to gain some portability in assembly language, usually by linking with a C library that does not change between operating systems.

For example, many things in libc depend on the preprocessor to do OS-specific, C-specific things to the program before compiling. In fact, some functions and symbols are not even guaranteed to exist outside of the preprocessor. Worse, the size and field order of structs, as well as the size of certain typedefs such as off_t, are entirely unavailable in assembly language without help from a configure script, and differ even between versions of Linux, making it impossible to portably call functions in libc other than ones that only take simple integers and pointers as parameters. To address this issue, FASMLIB project provides a portable assembly library for Win32 and Linux platforms, but it is yet very incomplete.[13]

Some higher level computer languages, such as C and Borland Pascal, support inline assembly where relatively brief sections of assembly code can be embedded into the high level language code. The Forth programming language commonly contains an assembler used in CODE words.

Many people use an emulator to debug assembly-language programs.

Example listing of assembly language source code

Address	Label	Instruction (AT&T syntax)	Object code
		`.begin`
		`.org 2048`
	`a_start`	`.equ 3000`
`2048`		`ld length,%`
`2064`		`be done`	`00000010 10000000 00000000 00000110`
`2068`		`addcc %r1,-4,%r1`	`10000010 10000000 01111111 11111100`
`2072`		`addcc %r1,%r2,%r4`	`10001000 10000000 01000000 00000010`
`2076`		`ld %r4,%r5`	`11001010 00000001 00000000 00000000`
`2080`		`ba loop`	`00010000 10111111 11111111 11111011`
`2084`		`addcc %r3,%r5,%r3`	`10000110 10000000 11000000 00000101`
`2088`	`done:`	`jmpl %r15+4,%r0`	`10000001 11000011 11100000 00000100`
`2092`	`length:`	`20`	`00000000 00000000 00000000 00010100`
`2096`	`address:`	`a_start`	`00000000 00000000 00001011 10111000`
		`.org a_start`
`3000`	`a:`

Example of a selection of instructions (for a virtual computer[15]) with the corresponding address in memory where each instruction will be placed. These addresses are not static, see memory management. Accompanying each instruction is the generated (by the assembler) object code that coincides with the virtual computer's architecture (or ISA).

Assembly language description

2008-10-23T18:50:00.000-07:00

An assembly language is a low-level language for programming computers. It implements a symbolic representation of the numeric machine codes and other constants needed to program a particular CPU architecture. This representation is usually defined by the hardware manufacturer, and is based on abbreviations (called mnemonics) that help the programmer remember individual instructions, registers, etc. An assembly language is thus specific to a certain physical or virtual computer architecture (as opposed to most high-level languages, which are usually portable).

Assembly languages were first developed in the 1950s, when they were referred to as second generation programming languages. They eliminated much of the error-prone and time-consuming first-generation programming needed with the earliest computers, freeing the programmer from tedium such as remembering numeric codes and calculating addresses. They were once widely used for all sorts of programming. However, by the 1980s (1990s on small computers), their use had largely been supplanted by high-level languages, in the search for improved programming productivity. Today, assembly language is used primarily for direct hardware manipulation, access to specialized processor instructions, or to address critical performance issues. Typical uses are device drivers, low-level embedded systems, and real-time systems.

A utility program called an assembler is used to translate assembly language statements into the target computer's machine code. The assembler performs a more or less isomorphic translation (a one-to-one mapping) from mnemonic statements into machine instructions and data. (This is in contrast with high-level languages, in which a single statement generally results in many machine instructions. A compiler, analogous to an assembler, is used to translate high-level language statements into machine code; or an interpreter executes statements directly.)

Many sophisticated assemblers offer additional mechanisms to facilitate program development, control the assembly process, and aid debugging. In particular, most modern assemblers (although many have been available for more than 40 years already) include a macro facility (described below), and are called macro assemblers.