CHAPTER 8
COMPUTER INSTRUCTIONS AND
MAN/MACHINE INTERFACES
INTRODUCTION
You have probably heard people talk about the various computer programming
languages used to write computer programs. Maybe you have even written some.
Programming languages include procedural-type languages. Examples are
COBOL (COmmon Business Oriented Language) to solve business-type problems,
and FORTRAN (FORmula Translation) to solve mathematical-type problems.
Other languages are interactive languages that enable a person to communicate with
a computer in a conversational mode to develop programs. BASIC (Beginner’s
All-purpose Symbolic Instruction Code) is an example of an interactive language.
Another language called Ada is the language developed for the Department of
Defense for use in embedded applications; for example, where a computer serves
as a control system. (Ada is named for Ada Augusta Byron, Countess of Lovelace,
for her achievements relating to computers. She was a full collaborator and
suggested the use of the binary system rather than the decimal system to Charles
Babbage, who is recognized as the father of computers.) These are all considered
high-level programming languages in that their instructions are in human readable
form, such as ADD A to B; LET X = Y; IF A > Y, THEN PRINT Y; and so on.
These types of instructions must be translated into machine code for execution by
a computer. This is accomplished through special language translation programs.
For high-level languages, a compiler program maybe used.
There are two other levels of computer languages: assembly language and
machine language. Assembly languages use mnemonics, symbols, to represent
operations. For example, “A” might mean add and “STR” might mean store. Like
high-level languages, these must be translated before a computer can execute the
instructions. To translate assembly language programs, an assembler program is
used.
By now, you have probably noticed that for an instruction to be executed, it
must be in machine code that consists of a series of 0’s and 1’s—the only things a
computer can understand. You have probably also realized that to write instructions
in 0’s and 1’s would be tedious, difficult, and time consuming. Therefore, the
assembly languages and the high-level languages provide easier means for people
to use to interface with computers to specify the steps a computer is to perform. As
a technician who is looking primarily at the internal functions of a computer, you
need to understand machine code and how it works. Some of the
operator/maintenance panels display information in binary, as you have already
learned. It will be up to you to interpret codes as meaningful information. Other
displays present information in commonly used words, terms, and numbers. In
these cases a computer, through program instructions, translatet/interprets the
binary codes into meaningful information. This information is then presented to
you.
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