BLACKBOARD (16K ZX81)
by Ian Rodgers, Wiltshire
from ZX Computing (December 1984/January 1985), page 152

Use your TV screen as a blackboard with this program from Wiltshire's Ian Rodgers.

Ian has produced a neat and comprehensive variation on the "drawing" program in which the screen is inverted and you chalk your pictures on it.

Although not a long program, it needs 16K because the whole screen is used.

Notice how all eight directions are provided plus checking for the screen edges all in TWO lines - 165, 170.

Instructions are provided in the program and it's well worth typing in. No more messy chalk dust getting up your nose!