SCPI commands follow a tree-like structure, 
organized into nodes. Each level of the command 
tree is a node. Each keyword in a SCPI command 
represents each node in the command tree. Each 
keyword (node) of a SCPI command is separated 
by a colon (:). 
For example, the diagram below shows an SCPI 
sub-structure and a command example.  
There are a number of different instrument 
commands and queries. A command sends 
instructions or data to the unit and a query 
receives data or status information from the unit.