Section 4: Programming 277

Identifying Stops

Blinking Display Stops. Errors that cause a blinking zero display, if executed in a program, also stop the program. You can identify the stop by switching momentarily to W/PRGM to see the code of the offending operation.
Normal Stops. To confirm that a program stops normally (i.e., via a RTN or R/S) switch momentarily to W/PRGM position and observe the displayed code. It should be 24 or 84.
Accidental Stops. Remember, that pressing any key will stop a program. Be careful to avoid pressure on the keyboard during program operation.
Cued Stops. If memory space permits, it is sometimes helpful to put a familiar number into the X register before stopping for data. Thus when the program stops, the displayed number identifies the desired input. For example if your program requires 8 stops for input, it is very helpful to have the numbers 1, . . . , 8 appear so you know which input is needed.
If a cue number is created as a program step immediately preceding the R/S, it is not lifted into the stack and the number is overwritten by the data you key in. (Cue numbers generated by other means will be lifted.)

Concerning W/PRGM Mode Display

Another feature of the W/PRGM display is that it allows you to see the last key pressed in a series of manual operations (except program operations). For example, in RUN mode you intend to key in
4.032 +
when the phone rings. After talking on the phone you can’t remember whether or not you pressed the + key. Switch to W/PRGM; you will see 61 if you pressed +.
If you have been calculating manually, and then wish to display a program, pressing SST will resume the program memory display.