How do I increase a variable by 2?
I am using Assembly x86 and TASM.
Thanks for help.
Try this :
.stack 100h
.data
my_var dw ?
.code
mov ax,#data
mov ds,ax
mov my_var, 5
add my_var, 2 ;<=== INCREASE BY 2 ( 5+2 ).
mov ax,4c00h
int 21h
If you are using IDEAL mode :
add [ my_var ], 2 ;<=== INCREASE BY 2 ( 5+2 ).
Related
#include "msp430g2553.h" // #include <msp430.h> - can be used as well
;-------------------------------------------------------------------------------
ORG 0x1100h
ID_F DB 0,3,9,1,0,4,9,0
ID_S DB 0,5,1,8,9,3,9,1
Size DW 16
;-------------------------------------------------------------------------------
MODULE PortLeds
PUBLIC First_SW, Second_SW, Third_SW;, Else_SW
;EXTERN ;Delay_Sec
RSEG CODE
;-------------------------------------------------------------------------------
;-------------------------------------------------------------------------------
Third_SW BIT.B #0x04, &P1IN
CLR R10 ; Index register
THIRD_LOOP MOV.B ID_F(R10), R15 ; Counter from 0 to ff-255
MOV.B R15, &P2OUT ; Save value
MOV.B #0x06, R13
Wait3 mov.w #0xFFFF,R14 ; Delay to R14
L3 dec.w R14 ; Decrement R14
jnz L3 ; Delay over?
DEC.B R13
JNZ Wait3
INC R10
CMP Size, R10
JL THIRD_LOOP
For some reason, when I am Third_SW, I reach this error:
pre_lab3_function.s43
Error[6]: Bad constant C:\Users\blala\OneDrive\Desktop\lab_3_new\pre_lab3_function.s43 3
Error while running Assembler
It appears on the org0110h, why is it happening? I am stuck for one day already because of it.
Any other code ( as you see its Third ) works pretty good, only Third which I need to use ID_F ID_S and Size, are the problem.
I wonder how I could optimize this code a little bit more. Now he has 467k and 59 lines.
Data segment:
code_char db 'A'
counter_space db 39
counter_char dw 1
counter_rows dw 25
Program segment:
rows:
mov cl, counter_space ;here I write space
mov ah,02h
mov dl,''
space:
int 21h
loop space
mov cx, counter_char ;here I write letters
mov ah,02h
mov dl,code_char
letters:
int 21h
loop letters
mov ah,02h ;here I go to another line(enter)
mov dl,0ah
int 21h
INC code_char ;here I change the value of variable's
DEC counter_space
ADD counter_char,2
DEC counter_rows
mov cx,counter_rows ;here I count the rows to 25
loop rows
mov ah,01h ;here I w8 to any key
int 21h
mov ah,4ch
mov al,0
int 21h
If you have any suggestions please comment.
I just started to learn Assembly.
You can make use of the fact that all other variables can be calculated from the counter_rows variable, so you really only need one variable:
code_char = 'A' + 25 - counter_rows
counter_space = counter_rows + 14
counter_char = 51 - counter_rows * 2
As counter_rows is your outer loop counter, you can just keep it in a register all the time instead of allocating memory for it. That makes it possible to run the program without any memory references at all.
There are some other small optimisations that can be done. You don't need to set the ah register to 02h other than for the first call. When setting ah to 01h for the keypress call, you can just decrement the register as you know that it was 02h before. You can set ax instead of setting ah and al separately.
If I counted correctly, this should take the actual code and data bytes down from 59 to 41:
mov bx, 25 ;counter_rows
rows:
;here I write space
mov cx, bx ; counter_space = counter_rows + 14
add cl, 14
mov ah, 02h
mov dl, 32 ;space
space:
int 21h
loop space
;here I write letters
mov cl, 51 ;counter_char = 51 - counter_rows * 2
sub cl, bl
sub cl, bl
;mov ah, 02h - already set
mov dl, 65 + 25 ;code_char = 'A' + 25 - counter_rows
sub dl, bl
letters:
int 21h
loop letters
;here I go to another line(enter)
;mov ah, 02h - already set
mov dl, 0ah
int 21h
dec bx
jnz rows
;here I wait for any key
dec ah ;02h - 1 = 01h
int 21h
mov ax,4c00h ;set ah and al in one go
int 21h
I am working on some code for my port of MikeOS. It is written in NASM x86 16 bit assembly. I am trying to change a variable that I made to have a different value. It compiles with no errors, but when I call os_print_string, it prints some wierd ASCII characters. Here is the code:
BITS 16
ORG 32768
%INCLUDE "mikedev.inc"
start:
mov si, test2 ; give si test 2 value
mov [test1], si ; give test 1 si's value
mov si, test1 ;now give test1's value to si
call os_print_string ; and print
test2 db "adsfasdfasdf", 0
test1 db "asdf", 0
This code is redundant, I know. I just need a n explanation on how to change a variable's value. Thaks in advance!
-Ryan
Another good old question, here is the answer you waited for 6.83 years :)
BITS 16
ORG 32768
%INCLUDE "mikedev.inc"
start:
mov si, test2
mov di, test1
.loop:
lodsb
or al, al
je .done
stosb
jmp .loop
.done:
mov si, test1
call os_print_string
test2 db "adsfasdfasdf", 0
test1 db "asdf ", 0
Make sure the char arrays have the same length or this will break ^^
But i am sure you know that by now ^^
I don't know what all the db, dw, dd, things mean.
I have tried to write this little script that does 1+1, stores it in a variable and then displays the result. Here is my code so far:
.386
.model flat, stdcall
option casemap :none
include \masm32\include\windows.inc
include \masm32\include\kernel32.inc
include \masm32\include\masm32.inc
includelib \masm32\lib\kernel32.lib
includelib \masm32\lib\masm32.lib
.data
num db ? ; set variable . Here is where I don't know what data type to use.
.code
start:
mov eax, 1 ; add 1 to eax register
mov ebx, 1 ; add 1 to ebx register
add eax, ebx ; add registers eax and ebx
push eax ; push eax into the stack
pop num ; pop eax into the variable num (when I tried it, it gave me an error, i think thats because of the data type)
invoke StdOut, addr num ; display num on the console.
invoke ExitProcess ; exit
end start
I need to understand what the db, dw, dd things mean and how they affect variable setting and combining and that sort of thing.
Quick review,
DB - Define Byte. 8 bits
DW - Define Word. Generally 2 bytes on a typical x86 32-bit system
DD - Define double word. Generally 4 bytes on a typical x86 32-bit system
From x86 assembly tutorial,
The pop instruction removes the 4-byte data element from the top of
the hardware-supported stack into the specified operand (i.e. register
or memory location). It first moves the 4 bytes located at memory
location [SP] into the specified register or memory location, and then
increments SP by 4.
Your num is 1 byte. Try declaring it with DD so that it becomes 4 bytes and matches with pop semantics.
The full list is:
DB, DW, DD, DQ, DT, DDQ, and DO (used to declare initialized data in the output file.)
See: http://www.tortall.net/projects/yasm/manual/html/nasm-pseudop.html
They can be invoked in a wide range of ways: (Note: for Visual-Studio - use "h" instead of "0x" syntax - eg: not 0x55 but 55h instead):
db 0x55 ; just the byte 0x55
db 0x55,0x56,0x57 ; three bytes in succession
db 'a',0x55 ; character constants are OK
db 'hello',13,10,'$' ; so are string constants
dw 0x1234 ; 0x34 0x12
dw 'A' ; 0x41 0x00 (it's just a number)
dw 'AB' ; 0x41 0x42 (character constant)
dw 'ABC' ; 0x41 0x42 0x43 0x00 (string)
dd 0x12345678 ; 0x78 0x56 0x34 0x12
dq 0x1122334455667788 ; 0x88 0x77 0x66 0x55 0x44 0x33 0x22 0x11
ddq 0x112233445566778899aabbccddeeff00
; 0x00 0xff 0xee 0xdd 0xcc 0xbb 0xaa 0x99
; 0x88 0x77 0x66 0x55 0x44 0x33 0x22 0x11
do 0x112233445566778899aabbccddeeff00 ; same as previous
dd 1.234567e20 ; floating-point constant
dq 1.234567e20 ; double-precision float
dt 1.234567e20 ; extended-precision float
DT does not accept numeric constants as operands, and DDQ does not accept float constants as operands. Any size larger than DD does not accept strings as operands.
I am doing some exercises in assembly language and I found a question about optimization which I can't figure out. Can anyone help me with them
So the question is to optimize the following assembly code:
----------------------------Example1-------------------------
mov dx, 0 ---> this one I know-> xor dx,dx
----------------------------Example2------------------------
cmp ax, 0
je label
----------------------------Example3-------------------------
mov ax, x
cwd
mov si, 16
idiv si
----> Most I can think of in this example is to subs last 2 lines by idiv 16, but I am not sure
----------------------------Example4-------------------------
mov ax, x
mov bx, 7
mul bx
mov t, ax
----------------------------Example5---------------------------
mov si, offset array1
mov di, offset array2
; for i = 0; i < n; ++i
do:
mov bx, [si]
mov [di], bx
add si, 2
add di, 2
loop do
endforloop
For example 2, you should look at the and or test opcodes. Similar to example 1, they allow you to remove the need for a constant.
For example 4, remember that x * 7 is the same as x * (8 - 1) or, expanding that, x * 8 - x. Multiplying by eight can be done with a shift instruction.
For example 5, you'd think Intel would have provided a much simpler way to transfer from SI to DI, since that is the whole reason for their existence. Maybe something like a REPetitive MOVe String Word :-)
For example three, division by a power of two can be implemented as a right shift.
Note that in example 5, the current code fails to initialize CX as needed (and in the optimized version, you'd definitely want to do that too).