of Microprocessors

148 MUSICAL ApPLICATIONS OF MICROPROCESSORS
beginning to show potential. Both have a long way to go before computers
can be used by conversing with them. Speech synthesis devices will be briefly
described in Chapter 20.
Microcomputer Software
Software, of course, is the key to a useful microcomputer system
regardless of the amount of memory or other peripheral devices available.
While much of the software that will be discussed in succeeding chapters is
specialized for music synthesis, a considerable amount of standard support
software is used in all general-purpose microcomputer systems. Although the
term "standard" is used, there is considerable variation in implementaion and
use details according to the individual manufacturer's pqilosophy. Most of the
discussion will be centered around the support software required for program
development in assembly language, although much of it applies equally well
to compiler languages. Conversely, the vast body of business software such as
word processors, spreadsheets, databases, and "business" graphics packages
that has been developed for microcomputers recently is of little interest here
and will not be considered further.
System Monitor
The most fundamental piece of support software is the system monitor.
With very few exceptions, microcomputers are unlike minicomputers in that
the traditional "programmer's console" with dozens of toggle switches and
lights is absent. Instead, a system monitor program is used to allow
equivalent console functions to be performed through the primary interactive
I/O device, such as a keyboard/display. All system monitors have the
capability of reading memory, modifying memory, examining the microprocessor
registers, and controlling the loading, dumping, and execution of
programs. More comprehensive monitors have debugging functions such as
search memory and breakpoints or program trace. Sometimes these and other
debugging functions are part of a separate debugger program.
Systems using a floppy disk term their monitors "disk-operating
systems," or DOS. In addition to the basic console and debugging functions
outlined above, DOS controls the allocation of disk space, finds and creates
files given a mnemonic name, and does other disk housekeeping chores.
Through DOS, the user may request a disk index listing, delete an unwanted
file, copy files from one disk to another, specify programs to be loaded by
name, and read or write data files a character at a time. DOS handles all of
the blocking or unblocking of characters to make full disk sectors. An
important DOS feature is the ability to do all of these tasks on command
from a user program as well as with console commands.