HP F2215AA HP 35s scientific calculator - User Guide - Page 211

14 Programming Techniques Chapter 13 covered the basics of programming. This chapter explores more sophisticated but useful techniques: Using subroutines to simplify programs by separating and labeling portions of the program that are dedicated to particular tasks. The use of subroutines also shortens a program that must perform a series of steps more than once. Using conditional instructions (comparisons and flags) to determine which instructions or subroutines should be used. Using loops with counters to execute a set of instructions a certain number of times. Using indirect addressing to access different variables using the same program instruction. Routines in Programs A program is composed of one or more routines. A routine is a functional unit that accomplishes something specific. Complicated programs need routines to group and separate tasks. This makes a program easier to write, read, understand, and alter. A routine typically starts at a label and ends with an instruction that stops program/ routing execution such as RTN or STOP. Calling Subroutines (XEQ, RTN) A subroutine is a routine that is called from (executed by) another routine and returns to that same routine when the subroutine is finished. Programming Techniques 14-1