How do you print graphics using SQR?

Atari BASIC had no implementation of user functions. However, programmers could simulate user functions because of the way the GOSUB command could reference a variable. For example, a programmer could start a subroutine at line 10000 and have the program initialize a variable with that number, i.e. "TEST = 10000". When that subroutine was needed the program could load some predetermined variables then use the command "GOSUB TEST". The subroutine at line 10000 would do its operation on the predetermined variables and could put a return result in another predetermined variable.