How to use for loop in Assembly?Why are loops always compiled into “do…while” style (tail jump)?8086 ASM: Turbodebugger opens text file, executing normally doesn'tSorting strings in 8086 AssemblyUsing Jump and Compare in Assembly LanguageReplacing a 32-bit loop counter with 64-bit introduces crazy performance deviationsmov ah,01h int16h, how to use it to change the direction of the snakeSnake Assembly 8086: not moving correctlySnake Game Assembly: increasing body length not workingSnake Game: how to know if it bites itselfHow do i re-write this assemly lang.program so that it can double any number passed to itC++ code for testing the Collatz conjecture faster than hand-written assembly - why?
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How to use for loop in Assembly?
Why are loops always compiled into “do…while” style (tail jump)?8086 ASM: Turbodebugger opens text file, executing normally doesn'tSorting strings in 8086 AssemblyUsing Jump and Compare in Assembly LanguageReplacing a 32-bit loop counter with 64-bit introduces crazy performance deviationsmov ah,01h int16h, how to use it to change the direction of the snakeSnake Assembly 8086: not moving correctlySnake Game Assembly: increasing body length not workingSnake Game: how to know if it bites itselfHow do i re-write this assemly lang.program so that it can double any number passed to itC++ code for testing the Collatz conjecture faster than hand-written assembly - why?
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I was tasked to do a code that would output the equal amount of 'Text Here' depending on the user input. However, I seem to get bewildered by my cmp function.
;Get keyboard input
mov ah, 01h
int 21h
;Save to bl for later use
mov bl, al
jmp isa
isa:
mov ah, 09h
mov dx, offset text
int 21h
cmp bl, bl
jne isa
je exit
What I get with this code is only one output of 'Text' no matter what number I input.
EDIT: I tried this but now my output is infinite :(
isa:
inc bl
mov ah, 09h
mov dx, offset ulit
int 21h
cmp bl, 30h
jne isa
je exit
assembly x86 dos
asked Mar 23 at 3:06
SifengSifeng
11
|
show 2 more comments
I was tasked to do a code that would output the equal amount of 'Text Here' depending on the user input. However, I seem to get bewildered by my cmp function.
;Get keyboard input
mov ah, 01h
int 21h
;Save to bl for later use
mov bl, al
jmp isa
isa:
mov ah, 09h
mov dx, offset text
int 21h
cmp bl, bl
jne isa
je exit
What I get with this code is only one output of 'Text' no matter what number I input.
EDIT: I tried this but now my output is infinite :(
isa:
inc bl
mov ah, 09h
mov dx, offset ulit
int 21h
cmp bl, 30h
jne isa
je exit
assembly x86 dos
asked Mar 23 at 3:06
SifengSifeng
11
As written, this should be an infinite loop, because you never decrementBL. What istext? Is it terminated with a dollar sign as the DOS API expects?
– Cody Gray♦
Mar 23 at 4:43
@CodyGray: This iscmp, nottest. It's checking ifblis equal to itself, like asub same,samezeroing idiom. Based on the title, this is maybe a duplicate of my Q&A about looping (Why are loops always compiled into "do...while" style (tail jump)?), but the question body is more like how to usecmp. But IDK what they want as an exit condition, so close as unclear would be reasonable.
– Peter Cordes
Mar 23 at 4:48
Of course it is. The eyes see what they want to see. Not so sure about that duplicate marking, though, @Peter. I assume you were marking it as a canonical "how do I write a loop in asm?" question, but I don't think your answer there really shows that.
– Cody Gray♦
Mar 23 at 4:53
@CodyGray: yeah, you're right. It has some example loops, but all the text assumes the reader already understands the fundamentals of how loops work. I don't recall any particular tutorial Q&A about how to loop, but I'm sure there have been many answers that explain it in passing. :/
– Peter Cordes
Mar 23 at 4:57
@CodyGray Yes I'm sorry I forgot about the $ sign. 'Text' simply any is any text we would like to be looped.
– Sifeng
Mar 23 at 10:37
|
show 2 more comments
I was tasked to do a code that would output the equal amount of 'Text Here' depending on the user input. However, I seem to get bewildered by my cmp function.
;Get keyboard input
mov ah, 01h
int 21h
;Save to bl for later use
mov bl, al
jmp isa
isa:
mov ah, 09h
mov dx, offset text
int 21h
cmp bl, bl
jne isa
je exit
What I get with this code is only one output of 'Text' no matter what number I input.
EDIT: I tried this but now my output is infinite :(
isa:
inc bl
mov ah, 09h
mov dx, offset ulit
int 21h
cmp bl, 30h
jne isa
je exit
assembly x86 dos
asked Mar 23 at 3:06
SifengSifeng
11
I was tasked to do a code that would output the equal amount of 'Text Here' depending on the user input. However, I seem to get bewildered by my cmp function.
;Get keyboard input
mov ah, 01h
int 21h
;Save to bl for later use
mov bl, al
jmp isa
isa:
mov ah, 09h
mov dx, offset text
int 21h
cmp bl, bl
jne isa
je exit
What I get with this code is only one output of 'Text' no matter what number I input.
EDIT: I tried this but now my output is infinite :(
isa:
inc bl
mov ah, 09h
mov dx, offset ulit
int 21h
cmp bl, 30h
jne isa
je exit
assembly x86 dos
assembly x86 dos
asked Mar 23 at 3:06
SifengSifeng
11
asked Mar 23 at 3:06
SifengSifeng
11
edited Mar 23 at 10:43
Sifeng
asked Mar 23 at 3:06
SifengSifeng
11
asked Mar 23 at 3:06
SifengSifeng
11
asked Mar 23 at 3:06
SifengSifeng
11
11
As written, this should be an infinite loop, because you never decrementBL. What istext? Is it terminated with a dollar sign as the DOS API expects?
– Cody Gray♦
Mar 23 at 4:43
@CodyGray: This iscmp, nottest. It's checking ifblis equal to itself, like asub same,samezeroing idiom. Based on the title, this is maybe a duplicate of my Q&A about looping (Why are loops always compiled into "do...while" style (tail jump)?), but the question body is more like how to usecmp. But IDK what they want as an exit condition, so close as unclear would be reasonable.
– Peter Cordes
Mar 23 at 4:48
Of course it is. The eyes see what they want to see. Not so sure about that duplicate marking, though, @Peter. I assume you were marking it as a canonical "how do I write a loop in asm?" question, but I don't think your answer there really shows that.
– Cody Gray♦
Mar 23 at 4:53
@CodyGray: yeah, you're right. It has some example loops, but all the text assumes the reader already understands the fundamentals of how loops work. I don't recall any particular tutorial Q&A about how to loop, but I'm sure there have been many answers that explain it in passing. :/
– Peter Cordes
Mar 23 at 4:57
@CodyGray Yes I'm sorry I forgot about the $ sign. 'Text' simply any is any text we would like to be looped.
– Sifeng
Mar 23 at 10:37
|
show 2 more comments
As written, this should be an infinite loop, because you never decrementBL. What istext? Is it terminated with a dollar sign as the DOS API expects?
– Cody Gray♦
Mar 23 at 4:43
@CodyGray: This iscmp, nottest. It's checking ifblis equal to itself, like asub same,samezeroing idiom. Based on the title, this is maybe a duplicate of my Q&A about looping (Why are loops always compiled into "do...while" style (tail jump)?), but the question body is more like how to usecmp. But IDK what they want as an exit condition, so close as unclear would be reasonable.
– Peter Cordes
Mar 23 at 4:48
Of course it is. The eyes see what they want to see. Not so sure about that duplicate marking, though, @Peter. I assume you were marking it as a canonical "how do I write a loop in asm?" question, but I don't think your answer there really shows that.
– Cody Gray♦
Mar 23 at 4:53
@CodyGray: yeah, you're right. It has some example loops, but all the text assumes the reader already understands the fundamentals of how loops work. I don't recall any particular tutorial Q&A about how to loop, but I'm sure there have been many answers that explain it in passing. :/
– Peter Cordes
Mar 23 at 4:57
@CodyGray Yes I'm sorry I forgot about the $ sign. 'Text' simply any is any text we would like to be looped.
– Sifeng
Mar 23 at 10:37
As written, this should be an infinite loop, because you never decrement
BL. What is text? Is it terminated with a dollar sign as the DOS API expects?– Cody Gray♦
Mar 23 at 4:43
As written, this should be an infinite loop, because you never decrement
BL. What is text? Is it terminated with a dollar sign as the DOS API expects?– Cody Gray♦
Mar 23 at 4:43
@CodyGray: This is
cmp, not test. It's checking if bl is equal to itself, like a sub same,same zeroing idiom. Based on the title, this is maybe a duplicate of my Q&A about looping (Why are loops always compiled into "do...while" style (tail jump)?), but the question body is more like how to use cmp. But IDK what they want as an exit condition, so close as unclear would be reasonable.– Peter Cordes
Mar 23 at 4:48
@CodyGray: This is
cmp, not test. It's checking if bl is equal to itself, like a sub same,same zeroing idiom. Based on the title, this is maybe a duplicate of my Q&A about looping (Why are loops always compiled into "do...while" style (tail jump)?), but the question body is more like how to use cmp. But IDK what they want as an exit condition, so close as unclear would be reasonable.– Peter Cordes
Mar 23 at 4:48
Of course it is. The eyes see what they want to see. Not so sure about that duplicate marking, though, @Peter. I assume you were marking it as a canonical "how do I write a loop in asm?" question, but I don't think your answer there really shows that.
– Cody Gray♦
Mar 23 at 4:53
Of course it is. The eyes see what they want to see. Not so sure about that duplicate marking, though, @Peter. I assume you were marking it as a canonical "how do I write a loop in asm?" question, but I don't think your answer there really shows that.
– Cody Gray♦
Mar 23 at 4:53
@CodyGray: yeah, you're right. It has some example loops, but all the text assumes the reader already understands the fundamentals of how loops work. I don't recall any particular tutorial Q&A about how to loop, but I'm sure there have been many answers that explain it in passing. :/
– Peter Cordes
Mar 23 at 4:57
@CodyGray: yeah, you're right. It has some example loops, but all the text assumes the reader already understands the fundamentals of how loops work. I don't recall any particular tutorial Q&A about how to loop, but I'm sure there have been many answers that explain it in passing. :/
– Peter Cordes
Mar 23 at 4:57
@CodyGray Yes I'm sorry I forgot about the $ sign. 'Text' simply any is any text we would like to be looped.
– Sifeng
Mar 23 at 10:37
@CodyGray Yes I'm sorry I forgot about the $ sign. 'Text' simply any is any text we would like to be looped.
– Sifeng
Mar 23 at 10:37
|
show 2 more comments
1 Answer
1
active
oldest
votes
First of all, make sure that you initialize the BX register to zero before you start your loop:
...
xor bx,bx
isa:
...
To avoid the DOS interrupt to overwrite the contents of your (used) BX register, secure it on the stack (not sure about the calling conventions of DOS interrupts, was too long ago for me):
...
push bx
int 21h
pop bx
answered Mar 25 at 13:08
MartinMartin
862
add a comment |
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1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
First of all, make sure that you initialize the BX register to zero before you start your loop:
...
xor bx,bx
isa:
...
To avoid the DOS interrupt to overwrite the contents of your (used) BX register, secure it on the stack (not sure about the calling conventions of DOS interrupts, was too long ago for me):
...
push bx
int 21h
pop bx
answered Mar 25 at 13:08
MartinMartin
862
add a comment |
First of all, make sure that you initialize the BX register to zero before you start your loop:
...
xor bx,bx
isa:
...
To avoid the DOS interrupt to overwrite the contents of your (used) BX register, secure it on the stack (not sure about the calling conventions of DOS interrupts, was too long ago for me):
...
push bx
int 21h
pop bx
answered Mar 25 at 13:08
MartinMartin
862
add a comment |
First of all, make sure that you initialize the BX register to zero before you start your loop:
...
xor bx,bx
isa:
...
To avoid the DOS interrupt to overwrite the contents of your (used) BX register, secure it on the stack (not sure about the calling conventions of DOS interrupts, was too long ago for me):
...
push bx
int 21h
pop bx
answered Mar 25 at 13:08
MartinMartin
862
First of all, make sure that you initialize the BX register to zero before you start your loop:
...
xor bx,bx
isa:
...
To avoid the DOS interrupt to overwrite the contents of your (used) BX register, secure it on the stack (not sure about the calling conventions of DOS interrupts, was too long ago for me):
...
push bx
int 21h
pop bx
answered Mar 25 at 13:08
MartinMartin
862
answered Mar 25 at 13:08
MartinMartin
862
answered Mar 25 at 13:08
MartinMartin
862
answered Mar 25 at 13:08
MartinMartin
862
862
add a comment |
add a comment |
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As written, this should be an infinite loop, because you never decrement
BL. What istext? Is it terminated with a dollar sign as the DOS API expects?– Cody Gray♦
Mar 23 at 4:43
@CodyGray: This is
cmp, nottest. It's checking ifblis equal to itself, like asub same,samezeroing idiom. Based on the title, this is maybe a duplicate of my Q&A about looping (Why are loops always compiled into "do...while" style (tail jump)?), but the question body is more like how to usecmp. But IDK what they want as an exit condition, so close as unclear would be reasonable.– Peter Cordes
Mar 23 at 4:48
Of course it is. The eyes see what they want to see. Not so sure about that duplicate marking, though, @Peter. I assume you were marking it as a canonical "how do I write a loop in asm?" question, but I don't think your answer there really shows that.
– Cody Gray♦
Mar 23 at 4:53
@CodyGray: yeah, you're right. It has some example loops, but all the text assumes the reader already understands the fundamentals of how loops work. I don't recall any particular tutorial Q&A about how to loop, but I'm sure there have been many answers that explain it in passing. :/
– Peter Cordes
Mar 23 at 4:57
@CodyGray Yes I'm sorry I forgot about the $ sign. 'Text' simply any is any text we would like to be looped.
– Sifeng
Mar 23 at 10:37