Program Boundaries (LBL and RTN)

If you want more than one program stored in program memory, then a program needs a label to mark its beginning (such as   ) and a return to mark its end (such as  ).

Notice that the line numbers acquire an  to match their label.Program Labels

Programs and segments of programs (called routines) should start with a label. To record a label, press:

letter–key

The label is a single letter from A through Z. The letter keys are used as they are for variables (as discussed in chapter 3). You cannot assign the same label more than once (this causes the message ), but a label can use the same letter that a variable uses.

It is possible to have one program (the top one) in memory without any label. However, adjacent programs need a label between them to keep them distinct.

Programs can not have more than 999 lines.Program Returns

Programs and subroutines should end with a return instruction. The keystrokes are:



When a program finishes running, the last RTN instruction returns the program pointer to  , the top of program memory.

Using RPN, ALG and Equations in ProgramsYou can calculate in programs the same ways you calculate on the keyboard: