End

Start the iteration over — and, against expectations, without giving up the tick

easyYou need: How the processor works, Condition and branching

end has no fields. It does exactly one thing: it puts the number of lines in the program into @counter. That is past the edge, and a number past the edge resets the counter — so the program starts from the first line.

steptick 0

Operation0

=

+

End1

Operation2

=

+

@counter0number

loopsnullnull

afternullnull

Press “step” four times: loops becomes two and after stays empty. The line below end is unreachable — execution never gets to it.

The program loops without it anyway

That is the first thing to understand: end is not needed to make a program repeat. It starts over by itself when the lines run out.

end is needed when an iteration has to be cut short early: to leave a branch without running everything written below.

jump 4 greaterThanEq stock 100
set low 1
end
set low 0

Without the third line both branches would run one after the other. That is the lesson “Condition and branching”.

It does not give up the tick

Here is where the surprise lives. wait gives up the rest of the tick and end does not: it only moves the counter. If the processor still has instructions in its budget, it goes straight round the program again, in the same tick.

The same one-useful-line program on a hyper processor, 60 ticks:

Tail	Iterations per second
nothing	1475
end	738
wait 0	59

end is twice as slow as an empty tail for exactly one reason: it counts as an instruction itself, so the iteration went from one line to two. It gives no pause at all.

Silent failure

Hence a common mistake: putting end at the end of a program “so as not to load the processor”. It does not work — the load does not change. Only wait can give up a tick.

Note

The variables window shows how it works: after end, @counter holds the number of lines in the program, and on the next step it is zero. More about the counter as a variable is in “Advanced”.

Remember

• end puts the line count into the counter, and the program starts from the first line.
• It is not needed for repetition: the program loops anyway.
• It is needed to cut an iteration short — to leave a branch, for instance.
• end does not give up the tick and does not reduce the load.

Task

Replace end with wait 0 and run the example: after still stays empty — the line below is unreachable not because of end but because execution never gets there.

loops, though, behaves differently: with end the iteration finishes straight away, with wait 0 on the next tick.