Code Probe 1.1

Code Probe -- A machine-language monitor for the Commodore VIC-20.

Originally written in 1988 using a BASIC machine-language loader to POKE the program into RAM, the original PRG file has been disassembled in 2026 and expanded into a Kick Assembler source listing with the assistance of Claude Code. The assembled body is 2614 bytes, fitting within a VIC-1211A Super Expander cartridge's 2944-byte expansion-RAM budget at $0480-$0FFF.

Commands

Eight commands, single-character dispatch:

Command	Description
A	Alter -- in-place hex editor with auto-commit
CLS	Clear screen
D	Dump -- hex + PETSCII sidebar
EXIT	Return to BASIC
G	Go -- execute via JSR trampoline (user RTS-back)
L	Load (PRG mode or SEQ mode) from tape
R	Register display (read-only)
S	Save (PRG mode or SEQ mode) to tape

Requirements

• Commodore VIC-20 with the VIC-1211A Super Expander cartridge attached at runtime (Code Probe occupies the cartridge's 3 KiB expansion RAM).
• Tape device. The VIC-20 version only supports tape.
• Programs authored under Code Probe in the $1001-$1DFF user-ML region deploy to a stock unexpanded VIC-20. The cartridge is required only for the monitor itself.

Assets

• code-probe.tap -- Tape image containing the CODEPROBE PRG. Load with LOAD "CODEPROBE",1,1 then RUN or SYS 1152.
• user-manual.pdf -- Complete user manual: command syntax, dump examples, tutorials, memory map, quick-reference card, VICE-emulation appendix.
• Source code (zip / tar.gz) -- Auto-generated by GitHub. Curated via .gitattributes to contain only the assembly source, assembled PRG, manual PDF, and README.

Verification

• 3D Cube authoring round trip: cube assembled, transferred into the user-ML region under Code Probe, saved with S 1001 1DD4 01, then loaded and run on a cartridge-less stock VIC-20.
• Self-save round trip: Code Probe saves itself with S 0401 0EB5 01, reloaded via BASIC LOAD + RUN or SYS 1152.