Congratulations to ACS for being among the first to market serious software for the Jupiter Ace. Their assembler and disassembler packages are nicely presented and well documented.

CALLISTO is a two-pass assembler with its own editor. The assembler sits above ramtop address 25996 and the editor is contained in dictionary up to 17009. Source code goes into 17100 onwards. Lower case Zilog mnemonics (as they appear in Appendix A of the Ace manual) are used and real labels or any length are permitted. Facilities include separate loading and saving of source code, number entry in decimal or hex, use of Ace normal editing keys, and useful pseudo instructions and error messages. Code can be compiled to run at a location other than where it is stored, and can be relocated easily with BLOAD.

Unfortunately, the editor in dictionary is software protected and you can't VLIST, LIST or assemble straight into a parameter field. With no access to dictionary this feels a bit like flying blind. Why do assemblers always monopolise those areas of memory most likely to be needed for storing machine code? Never mind, Callisto is a thoroughly good program! Recommended.

After Callisto, the GANYMEDE disassemble is a bit of an anti-climax. Decimal start addresses only, no FIND YOURWORD addressing, and nu back scroll. Forward scroll is quite fast though, which makes it easy to zip upwards in memory, and it is possible to VLIST and LIST with this program. Options included are start, continue, restart, and exit. Ganymede reserves about 6K above ramtop at 26589 and uses only 306 bytes of dictionary. Mnemonics are accompanied by decimal numbers and bytes are listed in hex.