Branching and Looping
Although the instructions in a program normally are executed in order of their
program line numbers, in some situations it is desirable to have program execution
transfer or "branch" to a program line that is not the next line in program memory.
Branching also makes it possible to automatically execute portions of a program
more than once — a process called "looping."
The i (go to) instruction is used in a program to transfer execution to any
program line. The program line desired is specified by keying its two-digit line
number into the program line containing the i instruction. When the i
instruction is executed, program execution branches or "goes to" the program line
specified and then continues sequentially as usual.
You have already seen a common use of branching: the i00 instruction (that is
stored in program memory after the program you key in) transfers execution to
program line 00. A i instruction can be used to branch not only backward in
program memory — as in the case of i00 and as illustrated above — but also
forward in program memory. Backward branching is typically done to create
loops (as described next); forward branching is typically done in conjunction with
an o or m instruction for conditional branching (as described afterward).
File name: hp 12c_user's guide_English_HDPMBF12E44
Printered Date: 2005/7/29
Page: 103 of 209
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