What does "control" mean in Data Step processing?

[Simon80]

I was wondering if someone can explain what "control" means in the following:

"By default, at the end of the DATA step, the values in the program data vector are written to the data set as an observation, control returns to the top of the DATA step..."

It appears to have something to do with the flow of processing, but what is control? The computer processor?  Thank you for your help!

[Tom]

Program control is old school terminology for what part of the program is currently executing.  So a branching statement like an IF or a GOTO changes program control.  Look at this USENET post from 1983 for an example usage.

The Story of Mel

[RichardinOz]

In simple terms SAS has come to the end of the process for the data currently in the PDV and now will start again at the top of the data step code with the next refresh of data in the PDV.

Note that statements like Format and Length, which relate to the configuration of the data, and those like Retain and Array, which relate to the configuration of the process, are not executed each time.  They only need to be used once, before the first loop through the program code.

Richard

[Simon80]

Tom and RichardinOz,

Thank you for your responses.  They were very helpful!