Difference between revisions of "83Plus:Basic:While"

Revision as of 14:25, 9 December 2005

Synopsis

Token Size: 1 byte

Syntax:

While condition

command

End

The while command is used to execute a command or series of commands when a variable shares a given relationship with another variable or a value. A While command will continue to execute everything before the next End until the given condition is no longer met.

Comments

Use of a Goto statement within an While statement will cause an increase in memory allocation, leading to program slowdowns and eventually a MEMORY error. For example, the following code will eventually cause an error:

Lbl 0
While X=1
X+1->X
Disp X
Goto 0
End

If you must use a Goto within an While statement, it is possible to trick the 83+ into thinking the block ended by jumping to an otherwise unused label that uses an End statement followed by a jump to the proper label. For example, the above program could be rewritten like so:

0->X
Lbl 0
While X=1
X+1->X
Disp X
Goto 2
End
Return

Lbl 2
End
Goto 0

This would avoid the problem by causing the 83+ to terminate the While conditional prior to jumping.

Examples

:While X =/= 105
:Getkey -> G
:End

Or, if you desire the use of other operators, such as And, Or, or Xor:

:While X=5 and Y=/=3
:Input "",A
:A+X->Y
:End