Manwe_BK0010_Assembly_vc3-2022
Author: Manwe / SandS
Category: Christmas Challenge
System: BK0010
Language: Assembler PDPy11
Len source code: 285
Len exe file: 60 + 4-byte header for emulator
Len code only: 60
Instructions:
Install BK2010 or Gid emulator, place SXRUTVAW.bin to "Files" or "Bin" folder, run emulator and choose BK 0010 mode. After it is started, type MONIT in Basic to exit to Monitor (BIOS). Type M and hit Enter (means "Magnetic tape"). In the prompt type file name SXRUTVAW and hit enter. Now file is loded. Type S and hit Enter (means "Start").
Description:
There are two 8-bit counters in one 16-bit word: the length of horisontal/vertical lines, and the lenght of diagonal lines. This 16-bit value actually come from PC (program counter), so compiling the source from the right start address is important. Swapping bytes in the counter every cycle stage, I use one counter after another. After 8 lines the loop is over, so I decrease both counters, substracting 16-bit value from the pair of counters. Then I draw a smaller snowflake inside a bigger one. There are 5 nested snowflakes.
Initial horisontal position of the cursor also come from PC (low byte).
Data block in the end works like a couriouse CPU instruction that leads to halt, so I need no particular HALT instruction in the end of program.
Subtracting 71 (octal) from filename symbols, I get 8 ASCII codes of cursor directions. Actually I used this technic in the previous Vintage Computing Christmas Challenge and got 28-byte code, which is absolute winner! But I did not finished it in time, so I released my christmass tree after the deadline. I'm not sure is it cheating or not, but now I use this technic with no doubt, because I have no chanse to win anyway (I know, it's possible to draw the snowflake with much smaller code, using another algorithm).
Comments:
The Assembly version of my Basic program. I like to keep this way of drawing, I love the animation :)