Agilent Technologies 54621A Programmer's Manual page 18

Introduction to Programming
Program Data Syntax Rules
All numbers must be strings of ASCII characters. Thus, when sending the
number 9, you would send a byte representing the ASCII code for the character
9 (which is 57). A three-digit number like 102 would take up three bytes (ASCII
codes 49, 48, and 50). This is handled automatically when you include the entire
instruction in a string.
Embedded Strings
Embedded strings contain groups of alphanumeric characters, which are
treated as a unit of data by the oscilloscope. For example, the line of text written
to the advisory line of the instrument with the :SYSTEM:DSP command:
:SYSTEM:DSP "This is a message."
Embedded strings may be delimited with either single (') or double () quotes.
These strings are case-sensitive, and spaces act as legal characters just like any
other character.
1-12