mirror of https://github.com/Klaus2m5/VTL02.git
53 lines
2.0 KiB
Plaintext
53 lines
2.0 KiB
Plaintext
-----------------------------------------------------
|
|
VTL-2 for the 6502 (VTL02B)
|
|
Original Altair 680b version by
|
|
Frank McCoy and Gary Shannon 1977
|
|
2012: Adapted to the 6502 by Michael T. Barry
|
|
see source code for copyright notice
|
|
Thanks to sbprojects.com for a very nice assembler!
|
|
-----------------------------------------------------
|
|
2015: Revision B, with several space optimizations
|
|
(suggested by dclxvi) and enhancements (suggested
|
|
by mkl0815 and Klaus2m5).
|
|
|
|
The basic concepts of VTL-2 (Very Tiny Language):
|
|
http://www.altair680kit.com/manuals/Altair_680-VTL-2%20Manual-05-Beta_1-Searchable.pdf
|
|
|
|
The files:
|
|
VTL02B for the apple II & the sbprojects.com assembler:
|
|
vtl02ba2.asm
|
|
VTL02B for the Kowalski 6502 simulator
|
|
http://www.exifpro.com/downloads/6502_1.2.12.zip:
|
|
vtl02b_for_Kowalski.asm
|
|
|
|
New features in Revision B:
|
|
* Bit-wise operators & | ^ (and, or, xor)
|
|
Example: A=$|128) Get a char and set hi-bit
|
|
|
|
* Absolute addressed 8-bit memory load and store
|
|
via the {< @} facility:
|
|
Example: <=P) Point to the I/O port at P
|
|
@=@&254^128) Clear low-bit & flip hi-bit
|
|
|
|
* The space character is no longer a valid user
|
|
variable nor a "valid" binary operator. It is
|
|
now only significant as a numeric constant
|
|
terminator, and as a place-holder in strings and
|
|
program listings, where it may be used to improve
|
|
human readability, at a slight cost in execution
|
|
speed and memory consumption.
|
|
Example:
|
|
* (VTL-2)
|
|
1000 A=1) Init loop index
|
|
1010 ?=A) Print index
|
|
1020 ?="") Newline
|
|
1030 A=A+1) Update index
|
|
1040 #=A<10*1010) Loop until done
|
|
|
|
* (VTL02B)
|
|
1000 A = 1 ) Init loop index
|
|
1010 ? = A ) Print index
|
|
1020 ? = "" ) Newline
|
|
1030 A = A + 1 ) Update index
|
|
1040 # = A < 10 * 1010 ) Loop until done
|