78 Section 6: Programming Basics

corresponding label. If need be, the search will wrap around at the end of program memory and continue at line 000. When it encounters an appropriate label, the search stops and execution begins.

If a label is encountered as part of a running program, it has no effect, that is, execution simply continues. Therefore, you can label a subordinate routine within a program (more on subroutines in section 9).

Since the calculator searches in only one direction from its present position, it is possible (though not advisable) to use duplicate program labels. Execution will begin at the first appropriately labeled line encountered.

If an ´ A entry starts the search for ―A‖ here, it then proceeds downward through memory, wraps around to line 000, and stops at label ―A‖. Execution then starts and continues (ignoring any other labels) until a halt instruction.

000-

 

´bA

 

´b3

 

¦

(stop)

end of memory

 

Unexpected Program Stops

Pressing Any Key. Pressing any key will halt program execution. It will not halt in the middle of an operation. This instruction will be completed before the program stops.

Error Stops. Program execution is immediately halted when the calculator attempts an improper operation that results in an Error display.

To see the line number and keycode of the error-causing instruction (the line at which the program stopped), press any one key to remove the Error message, then switch to Program mode.

If the display is flashing when a program stops, an overflow condition exists (page 61). Press −=, or "9 to stop the blinking.

Abbreviated Key Sequences

In certain cases, an ´ prefix you might expect to include in a key sequence is not needed. The rule for using an abbreviated key sequence is: the ´ prefix key is unnecessary after any other prefix key. (Page 19 contains a list of prefix keys.)