SF (Sequence Focus) - You do things a step at a time, even when you're doing more than one thing at a time, each you do a step at a time. And the things you do can be or include doing the nine VIC commands. In Simple Terms: The typical "grab the next line of the active sequenced-file, or interactive user input, process the line for VIC variables and commands, then pass it (or its return values) to the device, program, program-port, etc. as set by OP, when there is something to pass on (not totally consumed by SF processing.) All this with optional user interactive editing during the steps of processing such input lines.