Loop Structures
Loop structures allow you to execute a block of
code repetitively. The following
loop structures are supported.
Nesting Loops
When you know how many times the loop is to
execute, For Next loops come in very handy.
For Next loops use an index variable that increment or decrement in value
on each repetition of the loop.
For index = start To
end [Step increment]
statements
Next index
index is the variable you wish to use as
the index variable
start is the numerical starting value for index
end is the numerical ending value for index
Step and increment are both
optional. If used, increment
is the value to be added to the index upon each iteration.
If increment is positive, the index will count up.
if increment is negative, the index will count down.
The following loop will count from 2 to 10
For
a = 2 to 10
Next
a
When using an index variable of type uByte,
counting down to 1 or up to 255 as follows will generate smaller faster code.
Dim x as uByte
For
x=100 To 1 Step 1
Next
x
For
x=0 To 255
Next
x
An Exit For statement will jump to the
statement immediately following the corresponding Next statement, for
early loop termination.
While condition
statements
Wend
While condition is true execute the statements.
The following example will
count from 0 to 9 on an ASCII terminal
a="0"
While a<="9"
Call putc(a): Call putc(" ")
a=a+1
Wend
Syntax:
Repeat count
statements
End Repeat
count must be a literal
where 0 < count < 257
Repeat statements count number
of times. A repeat loop is smaller
and faster than a For Next, or a While Wend loop.
This example will send 10 period
characters to the USART.
Repeat 10
Call putc(".")
End Repeat
A control structure can be
placed inside another control structure. These
structures can be nested as many levels as you like.
Sub nesting()
Dim x as uByte
Dim y as uByte
Dim z as uByte
For x=1 To 10
For y=10 To 1 Step 1
z=5
While z>1
z=z-1
Wend
Next y
Next x
End Sub