| ★ APPLICATIONS ★ PROGRAMMATION ★ ZAPP: Z80 ASSEMBLY PROGRAMMING PACKAGE ★ |
Z.A.P.P (Amstrad Computer User) | ZAPP (Popular Computing Weekly) | Z.A.P.P (Popular Computing Weekly) | ZAPP (CPC Magazin) |
Automatic Machine code development tools released for the Amstrad must expect to be compared with the official offering, Devpac. The first thing you notice about Zapp, a combined assembler, editor and monitor, is that it is considerably easier to use than the Amsoft program. Assembler mnemonics are entered at the bottom of the screen, the syntax is checked, and if you have given a valid instruction (or assembler pseudo-mnemonic), it is inserted in the listing displayed above. The position it takes, the Current Line, is marked by a cursor which can be moved around to allow the insertion or deletion of lines at any point. One time-saving feature of Zapp is that you never need to bother with line numbers; these are provided automatically, renumbering the routine as new lines are entered. The assembler uses a one-pass technique which speeds up assembly, but puts some restrictions on the user. Forward references must avoid offsets, so the instruction JRLABEL-*- 5 is illegal if the address Label is further down the listing. The monitor and disassembler are designed to work with your own program - they even display any labels that are known - but are clumsy when looking at other sections of memory. The monitor will single-step routines and insert breakpoints, but its “front panel" display (the report of the state of the CPU) could be better labelled and contain more information. After using Zapp for some time, I began to find some of its shortcomings tiresome -no DEFS or ENT pseudo-mnemonics and the slowness with which the screen cursor moves around. Most of all, the program runs in the 40-column mode, so if you add comments to your listing you find the display becomes ragged. I suspect that Amstrad Zapp is a fairly straight forward conversion from the Spectrum program. Hewson have patched the user RST for printing (as the Spectrum's RST 10). which is fair enough; but the manual gives the impression that the user RST will always print a character, when it normally causes a reset! While I can recommend Zapp to newcomers and dabblers in machine code, if you are intending to write a magnum opus then the extra money and patience needed to get to grips with Devpac will be worthwhile. Jeff Naylor , Popular Computing Weekly |
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