Remote Spectrum Monitor User Guide : Programming with SCPI : Subsystem Commands
 
Subsystem Commands
Subsystem commands control all instrument functions and some general purpose functions. All subsystem commands are identified by the colon used between keywords, as in :INITiate:CONTinuous.
The following information is provided for each subsystem command described in the following chapters.
• The command name, See Command Names.
• The path from the subsystem root command, See Hierarchical Command Structure.
• The query form of the command (if applicable), See Query Commands.
• The command title.
• A description of the purpose of the command.
• The data parameters used as arguments for the command, See Data Parameters. This may include the parameter type and the available parameter choices.
Command Names
Typical SCPI commands consist of one or more keywords, parameters, and punctuation. SCPI command keywords can be a mixture of upper and lower case characters. Except for common commands, each keyword has a long and a short form. In this manual, the long form is presented with the short form in upper case and the remainder in lower case. For example, the long form of the command keyword to control the instrument display is :DISPlay.
The short form keyword is usually the first four characters of the long form (example: DISP for DISPlay). The exception to this is when the long form is longer than four characters and the fourth character is a vowel. In such cases, the vowel is dropped and the short form becomes the first three characters of the long form. Example: the short form of the keyword :POWer is :POW.
Some command keywords may have a numeric suffix to differentiate between multiple instrument features such as multiple trace options. For example; keywords :TRACe[:DATA]{1|2|3}, :TRACe1, or :TRACe3.
Note 
In the previous paragraph, :TRACe is identical to :TRACe1. If a numeric suffix it not included in a command, the first option is implied. Curly brackets { } designate optional keyword parameters. Square brackets [ ] designate optional command keywords.
As with any programming language, the exact command keywords and command syntax must be used. The syntax of the individual commands is described in detail in the programming command chapters. Unrecognized versions of long form or short form commands, or improper syntax, will generate an error.
Long Format vs. Short Format
Each keyword has a long format and a short format. The start frequency can be specified by :SENSe:FREQuency:STARt or :SENS:FREQ:STAR. The capital letters in the command specification indicate the short form of the command. A mixture of the entire short form elements with entire long form elements of each command is acceptable. For example, :SENS:FREQuency:STAR is an acceptable form of the command. However, :SENS:FREQuen:STA is not an acceptable form of the command because :FREQuen is not the entire short or long form of the command element.