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Instructions
Instructions (both commands and queries) normally appear as a string
embedded in a statement of your host language, such as BASIC, Pascal, or C.
The only time a parameter is not meant to be expressed as a string is when
the instruction's syntax definition specifies <block data>, such as learnstring.
There are only a few instructions which use block data.
Instructions are composed of two main parts:
·
The header, which specifies the command or query to be sent.
·
The program data, which provide additional information needed to clarify
the meaning of the instruction.
Instruction Header
The instruction header is one or more mnemonics separated by colons (:)
that represent the operation to be performed by the instrument. The
command tree in chapter 5 illustrates how all the mnemonics can be joined
together to form a complete header (see chapter 5, "Programming and
Documentation Conventions").
The example in figure 1 is a command. Queries are indicated by adding a
question mark (?) to the end of the header. Many instructions can be used as
either commands or queries, depending on whether or not you have included
the question mark. The command and query forms of an instruction usually
have different program data. Many queries do not use any program data.
White Space (Separator)
White space is used to separate the instruction header from the program
data. If the instruction does not require any program data parameters, you do
not need to include any white space. In this manual, white space is defined as
one or more spaces. ASCII defines a space to be character 32 (in decimal).
Program Data
Program data are used to clarify the meaning of the command or query. They
provide necessary information, such as whether a function should be on or
off, or which waveform is to be displayed. Each instruction's syntax definition
shows the program data, as well as the values they accept. The section
"Program Data Syntax Rules" in this chapter has all of the general rules about
acceptable values.
When there is more than one data parameter, they are separated by
commas (,). Spaces can be added around the commas to improve readability.
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Introduction to Programming
Program Message Syntax
1–5
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