HP 33s hp 33s_user's manual_English_E_HDPM20PIE56.pdf - Page 161

Designing a Program The following topics show what instructions you can put in a program. What you put in a program affects how it appears when you view it and how it works when you run it. Selecting a Mode Programs created and saved in RPN mode can only be edited and executed in RPN mode, and programs or steps created and saved in ALG mode can only be edited and executed in ALG mode. You can ensure that your program executes in the correct mode by making RPN or ALG the first instruction in the program. 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. Program Returns Programs and subroutines should end with a return instruction. The keystrokes are: |– Simple Programming 12-3