ONE LINER: Jitterbox cursor

Submitted by S.Elliott on April 25, 2026 - 3:12pm

his precisely-timed machine code tricks a 2513 character generator into displaying a dancing-box at the current cursor position, despite the fact that the character generator contains only 64 character shapes -- none of which is a box-shape!

300:D8 48 8A 48 B1 28 29 BD

308:09 2D 91 28 08 CA E0 24

310:68 E9 00 48 B1 28 F1 28

318:29 10 51 28 91 28 09 10

320:F1 28 29 90 09 10 51 28

328:91 28 2C 00 C0 10 DE 68

330:68 AA 68 91 28 AD 00 C0

338:2C 10 C0 60

 

This one-liner takes advantage of ProDOS's extension to the IN# command, allowing the user to enter an address parameter to specify a new input routine.  After typing in the program and entering the command  IN#A$300  the cursor changes to a dancing box:

Tags: 
vaporlock
one liner
Content Type: 
Hacks

Comments

xot's picture

Submitted by xot on April 28, 2026 - 3:37pm.

There is an address typo in the last line of your code box.

Unfortunately, I couldn't get this to dance with any of my available emulators.

My mistake. It works under ProDOS.

S.Elliott's picture

Submitted by S.Elliott on April 28, 2026 - 3:54pm.
xot wrote:

There is an address typo in the last line of your code box.

Sure enough, thanks!

Fixed now.

PS: Even without ProDOS, you can make it just dance (no cursor) using CALL768