APLX supports a range of commands ('system commands') which are used to communicate directly with the system. They are not part of the APL language itself. APL system commands start with a right parenthesis:
)SAVE
The display generated by a system command cannot directly be used as the argument to a function. However, in APLX, system commands can be executed using the (execute) primitive:
LIB [1] © Show contents of library 0 [2] ')LIB' [3]
The output from executed system commands can be
captured in a variable or passed as an argument to a function:
X')SYMBOLS' X IS 1026, USED 21
See the reference section on System Commands for a full list of available commands.