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 three-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 gi000 instruction
(that is stored in program memory after the program you key in) transfers execution
to program line 000. A i instruction can be used to branch not only backward
in program memory — as in the case of gi000 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 a go or gm instruction for conditional branching (as