13

Programming Techniques

Chapter 12 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.

For example, look at the program for "Normal and Inverse–Normal Distributions" in chapter 16. Routine S "initializes" the program by collecting the input for the mean and standard deviation. Routine D sets a limit of integration, executes routine Q, and displays the result. Routine Q integrates the function defined in routine F and finishes the probability calculation of Q(x).

A routine typically starts with a label (LBL) and ends with an instruction that alters or stops program execution, such as RTN, GTO, or STOP, or perhaps another label.

Programming Techniques 13–1

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HP 33s Scientific manual Programming Techniques, Routines in Programs