of Microprocessors

MICROPROCESSORS 151
well as application programming. For example, an often-required program
function is incrementing a variable. Most languages require a whole
statement of the form A = A + I! which when compiled will almost
invariably result in at least three machine instructions: load from A, add
constant 1, store into A. In C, a variable can be incremented by writing A +
in an expression, which would normally compile into a single "increment
memory" machine instruction. There is also an excellent facility for handling
addresses (pointers), often lacking in other languages. Because of its
efficiency, C is often used in direct synthesis applications and in fact is
recommended for that application. The only real drawbacks to C are its
sometimes cryptic appearance and lack of direct support for sophisticated
data structures.
Many other languages are used as well. Pascal is becoming a very
popular teaching language in formal computer science courses. FORTRAN,
a very old language, is often available to make the task of converting
mainframe scientific software to microcomputers straightforward if not easy.
Other specialized mainframe languages such as COBOL (business) and LISP
(artificial intelligence) have microcomputer versions. A very large and
comprehensive language developed for the Department of Defense called Ada
is being implemented on large microcomputers and shows a promising
future.
As microprocessors become faster and microcomputers incorporate
mote memory, there is more interest now in writing all software in high-level
languages, not just specialized applications or one-shot problem solutions. In
many cases (but certainly not all!), the system's grearer power hides the
inefficiencies that can occur when system programs such as editors,
compilers, and even disk-operating systems. are written in a high-level
language.
Example Microprocessor Descriptions
The first edition of this book, completed in 1979, selected three major
musical application areas of microprocess.ors and then described the characteristics
of the "best" microprocessor for each. These were logic replacement,
synthesizer control, and direct synthesis for which the 6502, 8080, and
LS1-11, tespectively, were recommended. Besides the apparent one-for-three
shooting performance (the 8080 became obsolete and the LSI-11 was never
popular), most microprocessor applications now seem better divided into just
two areas: general-purpose systems and dedicated-function systems. Generalpurpose
systems, in which the user is aware of the operating system and often
does programming, are extensively used to control synthesizers and do direct
synthesis. Dedicated-function systems, in which the microprocessor is
"hidden" from the user, certainly cover logic replacement but also synthesizer
control and, to a growing extent, even direct synthesis.