Loops With Counters (Dse, Isg) - HP 33s User Manual

Loops with Counters (DSE, ISG)

When you want to execute a loop a specific number of times, use the
( increment ; skip if greater than ) or
to ) conditional function keys. Each time a loop function is executed in a program, it
automatically decrements or increments a counter value stored in a variable. It
compares the current counter value to a final counter value, then continues or exits
the loop depending on the result.
For a count–down loop, use
For a count–up loop, use
These functions accomplish the same thing as a FOR–NEXT loop in BASIC:
 variable = initial–value  final–value  increment
.
.
.
 variable
A DSE instruction is like a FOR–NEXT loop with a negative increment.
After pressing a shifted key for ISG or DSE (
prompted for a variable that will contain the loop–control number (described
below).
The Loop–Control Number
The specified variable should contain a loop–control number ±ccccccc.fffii, where:
±ccccccc is the current counter value (1 to 12 digits). This value changes with
loop execution.
fff is the final counter value (must be three digits). This value does not change
as the loop runs.
ii is the interval for incrementing and decrementing (must be two digits or
unspecified). This value does not change. An unspecified value for ii is
assumed to be 01 (increment/decrement by 1).
Given the loop–control number ccccccc . fffii, DSE decrements ccccccc to
ccccccc — ii , compares the new ccccccc with fff, and makes program execution
skip the next program line if this ccccccc
13–18
Programming Techniques
º «
º «
variable
¹ ª
variable
¹ ª
fff.
( decrement ; skip if less than or equal
º «
or
¹ ª
), you will be