Rockwell Automation 1771-DB Basic Module User Manual - Series A - Manual (Page 42)

Operating Functions
Chapter 5
5–5
The argument stack (A-stack) stores all constants that the BASIC Module
is currently using. Operations such as add, subtract,
multiply and divide
always operate
on the first two numbers on the argument stack and
return
the result to the stack. The argument stack is 203 bytes long.
Each floating point
number placed on the stack requires 6 bytes of
storage. The argument stack can hold up to 33 floating
point numbers
before
overflowing.
The control stack (C-stack)
stores all information associated with loop
control (i.e. DO-WHILE, DO-UNTIL,
FOR-NEXT, BASIC subroutines
and “PUSHed” or “POPed” values). The control
stack is 157 bytes long.
DO-WHILE and
DO-UNTIL loops use 3 bytes of control stack.
FOR-NEXT loops
use 17 bytes. The control stack contains enough
space
for up to 9 nestings of control loops.
5.2.12
Argument Stack
5.2.13
Control Stack