HP 7475a, Operation And Interconnection Manual

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require that you have a programming background. The manual sup­
plied with your prepackaged software contains complete instructions
for its use. If prepackaged software is not available for your applica­
tion, it will be necessary to learn the programming languages that the
computer and plotter understand.
What Programming Languages Do
I
Use?
Although there are many programming languages, it is probable that
your computer understands BASIC (Beginner's All·purpose Symbolic
Instruction Code). BASIC is a common programming language that is
used to tell your computer what to do. It uses statements that resemble
English, is easy to use, and enables you to perform many complex
operations. These operations include computation, data base manage­
ment, and conditional evaluation of data to control program branch­
ing. BASIC also includes input and output statements which allow
your computer to communicate with the plotter. Output statements are
used to send Hp·GL instructions
to
the plotter. Input statements are
used to read responses from the plotter. If you are new to BASIC
programming and want to learn, your computer store can probably
supply a good BASIC programming manuaL If you are using a Hewlett·
Packard computer, your computer programming manual contains com­
plete details of the BASIC language version that it implements.
In addition to the computer language, you must also understand the
plotter's language (HP·GL) or a high·level graphics programming lan·
guage, such as AG
1..
AGL (A Graphics Language)
AGL is implemented on Hewlett·Packard computers to simplify graphics
plotting. AGL statements are an extension of the BASIC programming
language. They consist of English words that are usually followed by
numeric parameters. These statements describe their graphics plotting
function and instruct the computer to send HP-GL instructions to the
plotter. One AGL statement often performs a task that would require
several HP-GL instructions to perform. Your HP computer documenta­
tion is the source of the information you need to write plotting programs
using AGL statements.
HP-GL (Hewlett-Packard Graphics Language)
HP-GL is the graphics programming language that is actually sent to
and understood by the plotter. HP-GL instructions consist of two-letter
mnemonics that are usually followed by numeric parameters. With the
exception of certain escape sequence instructions which are used for
control of interface functions in an RS-232-C environment, all data
received by the plotter is interpreted as HP-GL instructions. You can
include HP-GL instructions directly in the computer language output
PLOTTER OPERATION
2-3