The SCPI standard allows specification of parameters as character data, as in the following command:
TRIGger:SOURce {BUS|IMMediate|EXTernal}
where "BUS", "IMMediate", "EXTernal" is the possible values of the character data.
The character data has a long and short format, and the formats are specified in accordance with the same rules as described in Long and Short Formats.
Apart from that, the character data can be combined with numerical parameters. For example:
SENSe:FREQuency:STARt {MINimum|MAXimum|<value>}
The following specifications are acceptable:
SENSe:FREQuency:STARt MIN
SENSe:FREQuency:STARt maximum
SENSe:FREQuency:STARt 1000000