I'm sure it's been done before, but somebody might find this useful.
`Stopwatch
ink rgb(0,255,0),1
set text font "courier"
starttime=timer()
do
cls
if inkey$()="=" then start=1:starttime=timer():secs=0:tens=0:mins=0:tenmins=0
if inkey$()="-" then start=0
if start=1
time=timer()-starttime
secs=val(left$(str$(time/1000),2))
if secs>9 then :secs=0:tens=tens+1:starttime=timer()
if tens>5 then tens=0:mins=mins+1
if mins>9 then mins=0:tenmins=tenmins+1
endif
set text size 30
text 0,0,right$(str$(tenmins),1)+right$(str$(mins),1)+":"+right$(str$(tens),1)+left$(str$(secs),1)+"."+right$(str$(time),3)
set text size 10
text 0,30,"Start: '+'"
text 0,50,"Stop: '-'"
loop
