donbright / tinyasm Goto Github PK

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Tinyasm 8086/8088 assembler
by Oscar Toledo G. Oct/02/2019

https://nanochess.org/
https://github.com/nanochess/tinyasm

Tinyasm is a small assembler for 8086/8088 programs,
and it can work over a real PC XT machine. It requires
at least 128K of memory, maybe more.

It came to my attention that several people wanted to
assemble my boot sector games over real PC XT machines.

Unfortunately, nasm doesn't run over 8086/8088 processors,
and I couldn't find a compatible assembler!

So what does a programmer when doesn't find the required
tool? Start to code his own tool!

It took me 3 days to start from zero and get a working
assembler compatible with the nasm syntax, plus all the
directives I've used in my boot sector programs.

Using the same command line syntax as nasm:

  tinyasm -f bin rogue.asm -o rogue.img -l rogue.lst

There is also the -d option for defining labels:

  -dCOM_FILE
  -dCOM_FILE=1

It returns a non-zero error code when the assembled
file generates errors.

Thanks to tkchia for making it portable to ia16-elf-gcc,
removing DeSmet C warnings, and making it to return
error codes.

Thanks to humbertocsjr for contributing the INCBIN
command.


>> DIFFERENCES BETWEEN TINYASM AND NASM >>

The main difference is that Tinyasm won't insert long jumps
for miscalculated conditional jumps.

Labels are started with letter, underscore or period.
Case is insensitive.

Local labels are supported, and should start with period.
The local labels final name is derived from concatenation
of the last global label (not starting with period) and
the local label.

There is only support for 8086/8088 processors, and only
are implemented the following directives:

	%ifdef
	%ifndef
	%if
	%else
	%endif
	%include
	incline
	times 
	use16
	cpu 8086
	equ
	db
	dw

The following operators are implemented:

	|	Binary OR
	^	Binary XOR
	&	Binary AND
	<<	Shift to left
	>>	Shift to right
	+	Addition 
	-	Subtraction 
	* 	Multiplication 
	/	Division (unsigned 16-bit)
	%	Modulo operator
	(expr)	Parenthesis
	-	Unary negation

The following numbers are implemented:

	0b0000_0100	Binary, you can use underscore (it will be ignored)
	0xabcd		Hexadecimal.
	$0abcd		Hexadecimal (after $ the first digit must be a number)
	'a'		Character constant.
	10		Decimal.
	$$		Start address.
	$		Current address.

This assembler won't win a speed test ;) because the
internal implementation uses a linear search for the
instruction set, and it is also implemented as a kind
of regular expression subset for easier coding.


>> DEBUG NOTES <<

If you're building boot sector games with Tinyasm, then you
need the following info to load the game inside the boot
sector of a floppy disk.

You need to have DEBUG in your disk (included with the DOS
disks).

Do the following (replace filename as desired):

	DEBUG ROGUE.IMG
		Extract now your working disk and insert a blank one!!!
	A300
	MOV AX,0301
	MOV BX,0100
	MOV CX,1
	MOV DX,0
	INT 13
	JB 300
	INT 20
	RIP
	300
	G
		Now the boot sector is replaced with the program!!!


>> BUILDING THE ASSEMBLER >>

You can build your own executable for Tinyasm using the
C compiler Desmet C, version 3.1h available graciously at:

    http://www.desmet-c.com/

The compiler has many bugs and limitations, but it works for
tinyasm purposes, and it's freely available.

Supposedly it should support ANSI C, but I couldn't fit a
standard ANSI C function definition, so I had to code again
in C K&R for the first time in maybe 20 years!

You can find the "e.bat" file to assemble the compiler.

I provide an executable on the Git to save you some time.

There are test cases in the 'test' subdirectory that are
runnable with the "test.bat" file.

There is a test for the full instruction set of 8086/8088
(the same listing that appears in my book Programming Boot
Sector Games).

The test cases come from my own programs:

	https://github.com/nanochess/fbird
	https://github.com/nanochess/invaders
	https://github.com/nanochess/pillman
	https://github.com/nanochess/bootBASIC
	https://github.com/nanochess/bootOS
	https://github.com/nanochess/bootRogue


>> ATTENTION <<        

Would you like to learn 8086/8088 programming? Then you
must get my new book Programming Boot Sector Games including
a 8086/8088 crash course!

Now available from Lulu:

  Soft-cover
    http://www.lulu.com/shop/oscar-toledo-gutierrez/programming-boot-sector-games/paperback/product-24188564.html

  Hard-cover
    http://www.lulu.com/shop/oscar-toledo-gutierrez/programming-boot-sector-games/hardcover/product-24188530.html

  eBook
    https://nanochess.org/store.html

These are some of the example programs documented profusely
in the book:

  * Guess the number.
  * Tic-Tac-Toe game.
  * Text graphics.
  * Mandelbrot set.
  * F-Bird game.
  * Invaders game.
  * Pillman game.
  * Toledo Atomchess.
  * bootBASIC language.

After the success of my first book, if you need even
More Boot Sector Games then you must get this book!

  Soft-cover
    http://www.lulu.com/shop/oscar-toledo-gutierrez/more-boot-sector-games/paperback/product-24462035.html

  Hard-cover
    http://www.lulu.com/shop/oscar-toledo-gutierrez/more-boot-sector-games/hardcover/product-24462029.html

These are some of the example programs documented profusely
in the book:

  * Follow the Lights
  * bootRogue
  * bricks
  * cubicDoom
  * bootOS