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Section 9: Program Interruptions147
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In the next section
(section 10), you will see how ALPHA strings can
be used to make prompting for data simple—your programs can
actually ask you for data.
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Using PSE (Pause)
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The PSE (pause) instruction executed in a program
momentarily interrupts program execution and displays the contents of the
X-register. The length of the pause is slightly less than one second,
although more PSE instructions in subsequent
lines of a program can be used to lengthen viewing time, if desired.
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Each time a pause is executed, the PRGM annunciator blinks one time. This
lets you know that the program is running—even during a pause.
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During program execution, the only keys that are active are
R/S and ON .
However, during the execution of a pause, of a string of pauses, the
entire keyboard becomes active. You can actually input data to your program
during a pause.
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Pressing data entry keys during the execution of a pause causes the pause
instruction to be executed again (or until you have completed the
data entry). Data entry keys are: ALPHA ,
USER ,
g ,
0 through 9,
CHS , EEX ,
and all ALPHA characters.
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Pressing any other keys during a pause, that is, any keys not associated
with data entry, causes the pause to terminate and program execution
continuous. The pressed function is executed.
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Keyboard Stops
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As you know, pressing R/S form the keyboard
during a running program halts that program. The program may halt after
any line—if you set the calculator to PRGM mode after a program
is halted, you will see the line number and the instruction of the
next line to be executed.
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