Section 8

Program Branching

and Controls

Although the instructions in a program are normally executed sequentially, it is often desirable to transfer execution to a part of the program other than the next line. Branching in the HP-15C may be simple, or it may depend on a certain condition. By branching to a previous line, it is possible to execute part of a program more than once – a process called looping.

The Mechanics

Branching

The Go To (t) Instruction. Simple branching – that is, unconditional branching – is carried out with the instruction t label. In a running program, t will transfer execution to the next appropriately labeled program or routine (not to a line number).

The calculator searches forward in memory, wrapping around through line 000 if necessary, and resumes execution at the first line containing the proper label.

Looping. If a t instruction specifies a label at a lower-numbered line (that is, a prior line), the series of instructions between the t and the label will be executed repeatedly – possibly indefinitely. The continuation

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