The FAQ list for NBASM
This FAQ list is dated: 12 Aug 2007
Questions:
- FAQ0101 Why is NBASM in Beta form?
- FAQ0102 Why NBASM when there are so many other assemblers out there?
- FAQ0103 Where can I get the latest version of NBASM?
- FAQ0104 Where can I get support for NBASM and will it cost me?
- FAQ0105 What kind of programs can I make with NBASM?
- FAQ0106 What will I benefit from using NBASM over one of the other
assemblers out there?
- FAQ0201 If I get stuck on a project using NBASM and can't figure out why,
will you help me?
- FAQ1001 Why can't I jmp/jcc to a procedure name?
- FAQ2001 How do I use NBASM in OS development?
Answers:
=- FAQ0101 -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Why is NBASM in Beta form?
Teqhnicality, NBASM isn't even in Beta form. Beta is when you have a
release that should have all functions, but you need it to be tested.
Once tested, then it can become a full release. However, most people don't
understand this and 'Beta' is what I chose to keep some understanding
within the 'masses'. (If you feel that I am/was in the wrong here, let me
know)
=- FAQ0102 -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Why NBASM when there are so many other assemblers out there?
Some while ago (say about 10 years ago and 5 million projects ago) I was
interested in creating an assembler. I was also interested in learning
more about x86 assembly. I put the two together and created NBASM written
in x86 assembly. I might have plans to make it a self-assemblable
assembler some day, but there are a few disadvantages to that. The main,
being that if I don't have a working backup of both the source and the
executable, and make an error, I am stuck and can not fix the error.
(not very easily, anyway)
=- FAQ0103 -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Where can I get the latest version of NBASM?
At the time of this writing, you could get the lastest version at:
https://www.fysnet.net/newbasic.htm
=- FAQ0104 -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Where can I get support for NBASM and will it cost me?
At the time of this writing, you can get FREE support at:
https://www.fysnet.net/newbasic.htm
and e-mail support at:
fys [at] fysnet [dot] net
...It will cost you nothing...
=- FAQ0105 -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
What kind of programs can I make with NBASM?
You can make any kind of program your heart desires as long as it will
be ran on an Intel x86 based system.
Most of the time, it is used in DOS to create small .COM files.
However, it has been/is being used to create:
- The boot and loader code for FYSOS
https://www.fysnet.net/fysos.htm
- a fully capable DOS 5.x look alike Operating System
- with a few modifications, could assemble itself
- many, many, many small DOS utilities
- DOS TSRs used by many DOS users
- Do you have a large project you would like to have listed here :-)
=- FAQ0106 -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
What will I benefit from using NBASM over one of the other
assemblers out there?
NBASM has its advantages and disavantages compared to some of the other
assemblers available.
Advantages:
- NBASM is free
- NBASM is fully supported
- NBASM is a very easy assembler to learn and use
- NBASM is near MASM 5.1x compatible. Which means with little
modifications, you can assemble the MASM code in most books.
- Did I mention that MASM is free?
Disadvantages:
- NBASM is not completely finished and is always being worked on.
- NBASM does not fully support the later 32 bit instructions, though
it does support most of them.
- NBASM does not support many of the output formats as others do.
- Did I mention that NBASM was free.....
=- FAQ0201 -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
If I get stuck on a project using NBASM and can't figure
out why, will you help me?
Yes. Simply send a snippet of the code you are having trouble with,
and the current version of NBASM you are using to:
fys [at] fysnet [dot] net
=- FAQ1001 -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Why can't I jmp/jcc to a procedure name?
As long as you do not use the 'uses' directive on the 'proc' line,
you can use the procedure name as a label to jmp/jcc to.
However, if you use the 'uses' directive and you jump to
the top of the procedure using the label name of the proc, you
will be jumping to the top of the 'push xx' instructions that
where pushed by the 'uses' directive.
label_name proc near uses ax bx
[push ax] ; <--- what you don't see
[push bx] ; <--- what you don't see
.
.
.
cmp xx,xx
jne short label_name
.
.
[pop bx] ; <--- what you don't see
[pop ax] ; <--- what you don't see
; if you jumped back to label_name, you will still have
; at least one count of ax and bx on the stack and the
; following 'ret' will not return where you think it should.
ret
label_name endp
=- FAQ2001 -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
How do I use NBASM in OS Development?
The advantage of NBASM, is that it won't add anything to the
binary unless you specifically ask for it, or you are using the
.model tiny directive with out the 'org xxh' operand.
Also, NBASM will produce binaries that are OS independant. The
only OS independance is when you make a .com file for DOS, however
this is easily modified. (Please remember that writing OS depended
code will create an OS dependant binary, however, if you don't code
any OS dependant code in your source files, NBASM won't put any
OS dependant code in the binary).
For example, let's say I want to create a 32-bit Pmode binary that
will be loaded to physical address 0x00100000 (1 meg). All you
have to do is use the .386 and .pmode directives, plus the orgnf
operand.
.model tiny
.code
.386
.pmode
orgnf 00100000h
start: mov eax,offset start
mov ebx,offset end
.
.
.
.
jmp short $
end:
.end
To assembly, use
nbasm32 filename filename.bin
then using your boot code, loader code, or other code, simply
load filename.bin to offset 0x00100000 and jump to it. Remember
that the code is 32-bit protected mode code, so it assumes that
you already have set up a GDT and have the CS and DS selectors
set with a base of 0x00000000. If your selectors have a different
base, say 0x00100000 (1 meg) and you want to load your code to
0x00300000 (3 meg), simply do the following:
orgnf (00300000h - 00100000h)
The 00300000h being the physical offset where this code is loaded,
and the 00100000h being the base memory of the code selector.
NBASM can also be used as the 16-bit code to setup the GDT and
selectors. For example,
.model tiny
.code
.386
.rmode
; assuming we are at 3000:0000h, real mode
; loaded here by the boot code.
org 0000h
; 16-bit code here to set up the
; GDT and segment selectors.
; now move to unreal mode. Unreal mode is
; were you temporarily go to pmode, set up a
; data descriptor with a base of 0x00000000
; (or another base) and a limit higher than
; 64k. Then you come back to real mode.
; as long as you don't modify the segment register,
; you can use it and a 32-bit operand to move
; data from real mode (under a meg) to above
; the megabyte limit. Example below.
; now load the pmode code from disk using the
; BIOS, to a buffer under 1meg. (If the
; pmode code is fairly large, do it in multiple
; parts). Then use the following example
; to move the code to 0x00300000.
; example of the move:
; buffer is in the range ds:0000h and ds:FFFFh
; minus the size of the buffer.
;
; mov si,offset buffer
; mov edi,00300000h ; 3 meg
; mov ecx,512 ; 512 dwords
;@@: lodsd
; mov es:[edi],eax
; add edi,4
; dec ecx
; jnz short @b
;
; the above code assumes you set up a valid GDT
; with an entry that has a base of 0x00000000
; and a limit of at least 0x00300000+(512*4),
; and set the es selector to this entry while
; in pmode.
I will not go into how to set up a valid GDT and go into
unreal mode and/or pmode here since this doesn't pertain
to using NBASM. There are many examples on the internet
on how to do so.
I am an avid OS Developer fan. If you have any questions
on using NBASM in your OS Development, please let me know.
I would love to help you.
end of FAQ list
If you have a question/answer/comment/etc. please send them to:
fys [at] fysnet [dot] net