Hello all. I am taking a course in Computer Architecture. Part of that course is assembly. We are not learning the language but just understand how it pertains to computer architecture. Despite this I was given an assignment in which I must comment 3 programs given to me. I am finding this very hard since I do not already know the language and it is not being taught to us. Can someone please help me accomplish this. I have already started to comment, but please feel free to correct or criteque me.
Title prog1 Define and display numbers
;Name: Matthew Fierro
;The output will be the ASCII character associated with the data
.model small
.stack 100h
.data ; data segment
list db 31h, 32h, 33h, 34h
.code ; begin code
main proc
mov ax, @data ; initialize data segment
mov ds, ax ; moves the value from ax into ds
mov dl, [list]
mov ah, 2 ; subroutine number 2
int 21h ; calls the dos interrupt
mov dl, " "
mov ah, 2 ; put 2 into ah
int 21h ; calls the dos interrupt
mov dl, [list+1]
mov ah, 2 ; put 2 into ah
int 21h ; calls the dos interrupt
mov dl, " "
mov ah, 2 ; put 2 into ah
int 21h ; calls the dos interrupt
mov dl,[list+2]
mov ah, 2
int 21h ; calls the dos interrupt
mov dl, " "
mov ah, 2
int 21h ; calls the dos interrupt
mov dl, [list+3]
mov ah, 2
int 21h ; calls the dos interrupt
mov ax, 4c00h ; end of processing
int 21h ; calls the dos interrupt
main endp ; end of procedure
end main ; end of program
lol - sounds like the prof has found a back-handed way to make you learn assembler
at the same time, he's teaching you to remark your programs (a good first lesson)
truthfully, I can't see how you can learn architecture without a grasp of basic assembler, anyways
even though assembler is machine specific, you are going to be dealing with intel-based processors eventually
just so you understand, we don't generally do homework for students
I will give you one freebie
every programmer has a different style
normally, I would not remark every line in such detail
it is safe to assume that the reader knows the basics
otherwise, they'd be reading playboy
for class, mine might look like this...
TITLE prog1
;display a list of numeric characters
;Name: Dead-end Dave
;display ASCII numeric characters from a list, seperated by spaces
;------------------------------------------------------------------
.MODEL small
.STACK 100h ;256 byte stack
;------------------------------------------------------------------
.DATA
ChrList db '1234'
;------------------------------------------------------------------
.CODE
main PROC
mov ax,@data ;get data segment
mov ds,ax ;into DS register
cld ;direction = up
mov si,offset ChrList ;address of list
mov cx,sizeof ChrList ;number of characters
Loop1: lodsb ;character in AL
push cx ;save count
xchg ax,dx ;character in DL
push si ;save index
mov ah,2 ;function = display character
int 21h ;DOS function call
mov dl,' ' ;space character
mov ah,2 ;function = display character
int 21h ;DOS function call
pop si ;recall index
pop cx ;recall count
loop Loop1 ;until done
mov ax,4c00h ;terminate, return code=0
int 21h ;DOS function call
main ENDP
;------------------------------------------------------------------
END main ;entry is main
by the way - "list" is a reserved assembler word - can't use it for a label
Thanks. Actually I have quite an extensive background. I have a BS in Computer Programming and Information Systems. I am very familar with high-level languages like Java and C#. However I just recently started my masters in Computer Science. I was placed in a few undergraduate courses like computer architecture because my background was lacking. I am fully aware of proper commenting techniques. See the course I am taking is a crash course this summer. I am trying to knock out all of my prerequistes so I can become a full-time graudate student in the fall. The professor told us it would take him 1 or 2 semesters to teach us assembler, so instead he is just having us comment some programs to see that we understand "how to computer works".
oh - you might want to add these 6 lines between loop and mov ax,4c00h
.
.
.
loop Loop1 ;until done
mov dl,13 ;carriage return
mov ah,2 ;function = display character
int 21h ;DOS function call
mov dl,10 ;line feed
mov ah,2 ;function = display character
int 21h ;DOS function call
mov ax,4c00h ;terminate, return code=0
.
.
.
actually, there are more direct methods of displaying the string
if the string were defined as:
ChrList db '1 2 3 4',13,10,36
you could display them all at once with
mov ah,9
mov dx,offset ChrList
int 21h
you should become very proficient at assembly language
you will never regret the time spent getting started
it will give you much clearer insight to the inner workings of processors and operating systems
although - this is a 16-bit program - i suggest you learn 32-bit programming
btw - i am an EE with 30+years
if i was going to hire an MS, I would expect him to be proficient in windows 32-bit assembler
even if the software was to be C or any other language
you have to pay if you want an MS instead of a BS
really, based on what professors have told me, Computer Science people only need a "general" idea of hardware because CS is all software. According to my prof's it is the Computer and Electrical Engineers that need to be proficient in hardware.
Oh one last thing. I am currently running masm on a 32-bit operating system. Before that I was attempting to run it on a 64-bit system and was getting an error during the assembly process. Any reason why?
well - i am not sure - i do know that 16-bit code will not run on vista 64
maybe, it won't let you compile it, either
yah - when i was young, i wanted to get a phd in physics - lol
not much money in that, but it is what interested me
looking back, a business admin degree would have been more sensible and probably much easier to get
i think the guys with a technical degree and a business degree are most successful, monitarily
That is ironic. I also have full intentions of getting a PHD. I love to teach and help others. I also like taking lead roles. Professors have very secure jobs, especially in today's economy. I mean really have you ever heard of a professor being let go. It is a win win situation for me. Write now I attend NYIT. In the future I hope to attend NYU for my PHD.
ahhhh - to be young again - lol
i wish you all the best
are these comments any better, are they correct
Title prog1 Define and display numbers
;Name: Matthew Fierro
;The output will be the ASCII character associated with the data
.model small
.stack 100h
.data ; data segment
list db 31h, 32h, 33h, 34h ; use db to define each element as 2 byte
.code
main proc
mov ax, @data ;copy the address of the data
mov ds, ax ;segment(@data) into the ds register
mov dl, [list]
mov ah, 2 ;int 21 function 2 displays the characters in dl
int 21h ; calls the dos interrupt
mov dl, " " ; puts a space
mov ah, 2
int 21h
mov dl, [list+1] ;copy second byte to dl
mov ah, 2
int 21h
mov dl, " "
mov ah, 2
int 21h
mov dl,[list+2] ;copy third byte to dl
mov ah, 2
int 21h
mov dl, " "
mov ah, 2
int 21h
mov dl, [list+3] ;copy fourth byte to dl
mov ah, 2
int 21h
mov ax, 4c00h ; end of processing
int 21h
main endp ; end of procedure
end main ; end of program
Everyone has their own style of commenting a program, so I'm not going to say how I would comment it, but what I will tell you is that a comment is for explaining what the program is doing or about to do, what you shouldn't do is put a comment that says what the actual instruction is doing i.e.
mov ah,2 ;move 2 into ah register
This comment is useless & totally unecessary, hope this helps to put you on the right track :U
Thanks, but I understand what comments are used for. If you read my earlier posts, I explained that my assignment was to comment a program given to me. Problem is that the course is on computer architecture not assembler. I do not know assembler, nor do I have time to learn it in a 3 week summer class. So what I am asking is based on what research I have done, and based on help from others in this forum, do my comments reflect a correct understanding of what the code is doing. Our prof wants us to comment the code to show that we understand assembler as it pertains to computer architecture.
the one i commented is a good example
i modified the program because it was sooooo sloppy - lol
but, all i did was put the repeated instructions into a loop
so - use the comments from mine, and apply them to yours, less the loop
Matt, it seems like you are in a paradox: you don't want to (or can't) learn the assembler, but the instructor is pretty much expecting this of you. I mean, how else are you supposed to comment code unless you fully understand it?
I think the bottom line here is, if you really want to comment effectively (regardless of your "comment skill" and background), you must learn the material. I too am entrenched in the bunkers of college life, and when the instructor asks exceptional things, then only the exceptional students produce exceptional results.
That said, perhaps what would help is some definitions. Download the MASM32 package and see \masm32\help\opcodes.chm for each of those instructions. This will at least give you some idea what each one is doing. However there is no way around it, you're going to have to do some studying and research on your own time to nail this.
(Well, you could probably buy an answer at RentaCoder.com, but then you'd only be cheating yourself.) :bg
learning assembler is not hard, really
there is a lot of material, with regard to learning the API functions
you do not need to know all the API functions to write code
the thing is, most of us are here because we enjoy it
don't look at it like a task - make a hobby out of it - attitude is everything
in the end, you will find it fun and rewarding
:U
agree with you.
Hello it is me again. Here is another program I need to comment. I started to work at it, I am not asking for help, I just want to know if I am on the right track. By the way I spoke with my prof and the way he wants us to comment the program is to tell him what each instruction is doing.
.data
array db 10, 20, 30, 40, 50, 60, 70, 80, 90
arraysize dw 9
.code
main proc
extrn writeint:proc, crlf:proc ;Writeint.obj found in fierro.lib,Crlf.obj found in fierro.lib
mov ax, @data ;copy the address of the data segment
mov ds, ax ;@data into ds register
mov bx, offset array ;get the address of array into bx
mov cx, arraysize ;put arraysize into cx register
mov ax, 4
call delete
call printout
mov ax, 4c00h
int 21h
main endp
delete proc
add bx, ax ;add value in ax to value in bx
sub cx, ax ;subtract ax from value in cx
dec cx
repeat:
mov ax, [bx+1]
mov [bx], ax
inc bx
loop repeat
ret
delete endp
printout proc
mov si,0
mov cx, arraysize
dec cx ;decrement the cx register
again:
mov ah,0
mov al, [array + si]
mov bx, 10
call writeint ; in base 10 format
mov dl, " "
mov ah, 2 ;dispay character function
int 21h
inc si ;use si to count how many times we push onto the stack
loop again
ret
printout endp
end main
well - comments like "add value in ax to value in bx" don't tell the reader anything
the comments should tell the reader what is going on in the program
in other words, they should explain the purpose of the instructions, rather than the method of achieving it
let's call the "4" value an index
mov bx, offset array ;array pointer in bx
mov cx, arraysize ;array length (count) in cx
.
.
.
add bx, ax ;add index to pointer
sub cx, ax ;subtract index from count
What kind of homework is that. Commenting stuff... The teacher must be a noob with assembly.
:lol
oh my fo!
you are talking about teacher.
yes - if you read previous posts....
the prof said, "I am not going to teach you assembler because that would take 2 semesters"
or something to that effect
this is the second program we have seen from this prof
he should have said, "You will know more about assembler than I do at the end of the summer"
on another thread, the prof wants them to design a serial com circuit
i wonder if he needs it for a contract job ? - lol
(i have seen that happen quite a few times - the results can range anywhere from exceptional to crappy)
i usually don't like working with profs on a job
with one exception - Dr Dave Pheanis - a true wizard and a tough instructor (i know - lol @ the name)
at Sperry Flight Systems, he was in our group - a few of the other engineers had had him as an instructor
they were all afraid of him - lol
but, he is a nice guy as long as he isn't your prof
too bad he doesn't hang in here (probably no time)
http://www.fulton.asu.edu/fulton/people/page.php?profile=149
Quote from: Mark Jones on June 06, 2009, 05:57:59 PM
...
Download the MASM32 package and see \masm32\help\opcodes.chm for each of those instructions.
...
I just tried to run the program, and I guess my prof screwed up when he gave it to us because it contains two errors.
Line 27: repeate: error: missing operand after unary operator
Line 55: end main: error:unmatched macro nesting
repeat is a reserved word
delete might also be a reserved word - not sure - don't use words like that
in the delete proc - he has dec cx - take that out <--- not sure about that one
i lose the guy right there - not sure what he is trying to do
this code....
mov ax, [bx+1]
mov [bx], ax
needs to be this....
mov al, [bx+1]
mov [bx], al
yah - i don't know what the program is supposed to do - it is not well written - lol
fix the reserved words
make sure you copied the code correctly
i thought i knew what he was trying to do, but the code doesn't even come close to working - lol
I asked my prof. He said the program is supposed to remove the number 50 from the array. I asked him about the errors and he said, "I don't know how to fix".
did I mention that my prof is 65+, of Chinese decent, been in America for over 50 years, cannot speak a lick of English. The man does not teach, he talks to the blackboard and rarely addresses the class. Try sitting through that for 3 hours straight. I'd rather get a root canal.
lol
that rings a bell
one of my physics intructors was from Formosa
his name was - wait for it....... Dr Who
lol
he was actually a very sharp guy - kind of young
his specialty was optics, which is ok, but, at the time, wasn't one of my favorite parts of physics
i have become more interested in it over time
anyways, when we came to the part about reflection and refraction, it became very difficult to understand him
when a Chinese person says, "reflection", they quite often wind up saying "refrection"
hard to know whether we were talking "refrection" or "refraction" - lol
anyways, i liked Dr Who - he was a good guy - and i got an A - lol - that helps, too
i always liked physics anyways
ok - so put the dec cx back in
the ax,[bx+1] should be al,[bx+1]
the ax,[bx] should be al,[bx]
if you change the word "repeat" to some other name, that will get rid of one error
as for the main nesting error - it may be related to the repeat error, as that could have caused a phase error
but - i always put the names of procedures all the way to the left of the page when opening and closing procs
main proc
ret
main endp
like that - that might help
Thanks, I will let you know how I make out tomorrow.
Ok I fixed those errors and got the program to assemble. Next I linked the program and got the .obj file. However when I went to run the .exe I received 2 more errors.
CRLF - unresolved external
WRITEINT - unresolved external
yah - those are in a library someplace ?
you need to link with that library or obj file
up near the top, you want to add....
includelib fierro.lib
actually, I opened a new dos window and tried running the program again. This time I got no errors but received the black screen of death.
see the previous post
the writeint is a routine that converts binary to base ten (i guess)
CRLF is a carraige return/line-feed
you can see they are declared as externals
does the include go before the data, before the code, somewhere else at the top?
yes - before the data
i would move the extrn's up there also
Ok I think it is working now. the output is
10 20 30 40 60 70 80 90.
The number 50 was removed from the list.
if you use the includelib, you may not need the extrns
the difference is, with includelib, the assembler puts info in the OBJ file about where to find them
without includelib, you have to specify the obj when you link
link programname.obj+fierro.obj
something like that
cool - lol
now - the prof is gonna want your fixed version for the next semesters class - lol
LOL, funny you mentioned that. Well actually as I mentioned eariler, this is only an undergraduate prerequisit for me becasue my undergrad was not computer science. Next semester I am signed up for CSCI 641 which is graduate leve computer architecture. The class I am taking now is a prerequist for that. So it sounds to me like I will be visiting here often for some much needed guidance.
well - your new prof will probably know assembler
that will help, but it will also mean he will want you to learn
if you google Iczelion's Tutorials - a good place to start
if i were you, i'd be a step ahead of the game and play with it a little before you get to 600 level class
also - learn 32-bit code
16-bit code is quickly becoming a thing of the past
well I only have another two weeks of this class and that gives me the rest of the summer to work on it.
you know what else is funny. CSCI641, Graduate computer architecture is the only hardware class I am forced to take in my MS. the rest of the courses are all software.
Now back to that annoying logic diagram.