The Micro User
1st December 1984
Fmon has that rare substance - quality
Pronounced eff-mon rather than Fmon, this is a simple package consisting of a program on tape and a manual.
The brief from Fsoft describes it as a powerful machine code monitor for the BBC Micro. On the surface it appears similar to other available packages, some of which are provided in ROM.
However, despite appearances this is a program somewhat out of the ordinary. It is good software, professional and complete, complex but under no pretence as to its limitations, well written and adequately explained.
It is a package which exudes that intangible substance - quality.
To back up this statement, it is necessary to explain what it does. To quote the manual again, it includes "a disass embler, a relocator, a line assembler, a trace mode, break points, user defined variables, fully recursive procedures and full support of MOS and VDU commands".
In other words if you wish to debug machine code programs, write small test programs in assembler, develop ROM based software, or simply satisfy your curiosity about the contents of memory, all that is required is to load this into a spare(?) 5k and set off.
At the programmer's disposal are a number of one letter commands which can be strung together into sentences or used in isolation.
The commands fall into three categories, the first of which allows manipulation of numbers in three general purpose registers called system variables. The second category use the numbers in the system variables as arguments when performing various tasks.
These include block moves, disassembly, subroutine jumps, tracing, hex and Ascii dumps of memory, string searches and a very powerful machine code relocation command — to mention but a few of the many available.
> The third category might be termed miscellaneous com mands. These do not use the system variables but merely serve to make the package more powerful and easier to use.
The most notable of these powerful features is definition of fully recursive procedures - macros - and user variables.
These can be saved and restored from disc or tape so a number of standard macros can be defined for commonly used operations —the example given in the documentation is a hex dump of zero page. p> It is designed to serve those familiar with the workings of the BBC Micro and with 6502 machine code. Given this, programmers should seriously consider including it as a prized utility in their toolbox.
David Williams
Screenshots
