SNOW
Author: regregex
Category: Christmas Challenge
System: BBC Micro A/B/Master, Acorn Electron
Language: 6502 assembler (MASM)
Len source code: 374 bytes
Len exe file: 80 bytes
Len code only: 80 bytes
Instructions:
Install and open BeebEm ( http://www.mkw.me.uk/beebem/ ).
Click File -> Disc Options -> New Disc 0, enter bbcsnow.ssd
Click Edit -> Import Files to Disc -> Disc 0, select xbbcsnow.inf
At the BASIC prompt, type */X.BBCSNOW and press RETURN.
To reproduce the screenshots:
Click Hardware -> BBC Model -> BBC Master 128
Enter the following:
*INSERT 9
*CONFIGURE FILE 9
*CONFIGURE MODE 4
Press Ctrl+F12 (CTRL+BREAK), releasing Ctrl last.
Then follow the instructions above.
To show the editor screen, import bbcsnow.inf as above, then enter:
*EDIT BBCSNOW
Shift+F5, 4, RETURN hides the function key display.
Shift+F10 (SHIFT+F0) hides newline markers.
Description: The program displays a specific snowflake pattern on the
screen.
It selects display MODE 4, which automatically clears the screen.
For each character cell in a rectangle left of the centre line it prints
an asterisk, if marked on one of two copies of a bitmap, or if lying on
an axis; otherwise a space is printed. The characters chosen are pushed
on the stack and popped in reverse order to print the right half of the
pattern. The program waits for a keypress before exiting.
Comments:
Suitable for an SBC running BASIC if selection of MODE 4 is removed.
Delete values ,4,22 from the source or patch the binary with bytes
&FF, &FF.
