Using Flags

Pressing {xdisplays the FLAGS menu: { } {} { @}

After selecting the function you want, you will be prompted for the flag number (0–11). For example, press {x{ } 0 to set flag 0; press

{x{ } Œto set flag 10; press {x{ } Œ1 to set flag 11.

FLAGS Menu
Menu Key

Description

 

 

{} n Set flag. Set flag n.

{} n Clear flag. Clears flag n.

{ @} n Is flag set? Tests the status of flag n.

A flag test is a conditional test that affects program execution just as the comparison tests do. The FS? n instruction tests whether the given flag is set. If it is, then the next line in the program is executed. If it is not, then the next line is skipped. This is the "Do if True" rule, illustrated under "Conditional Instructions" earlier in this chapter.

If you test a flag from the keyboard, the calculator will display "& " or "".

It is good practice in a program to make sure that any conditions you will be testing start out in a known state. Current flag settings depend on how they have been left by earlier programs that have been run. You should not assume that any given flag is clear, for instance, and that it will be set only if something in the program sets it. You should make sure of this by clearing the flag before the condition arises that might set it. See the example below.

Example: Using Flags.

The "Curve Fitting" program in chapter 16 uses flags 0 and 1 to determine whether to take the natural logarithm of the X– and Y–inputs:

Lines S03 and S04 clear both of these flags so that lines W07 and W11 (in the input loop routine) do not take the natural logarithms of the X– and Y–inputs for a Straight–line model curve.

13–12 Programming Techniques

File name 32sii-Manual-E-0424

 

Printed Date : 2003/4/24

Size : 17.7 x 25.2 cm