SKETCH-PAD (ZX81)
by Eric Deeson, Highgate, Birmingham
from Your Computer (August/Septemebr 1981), page 65

The program runs in 1K. However, more memory is needed for sophisticated
designs using most of the screen. A three-character input is expected during
each loop - or "S" to stop. The first is any keyboard character or symbol;
the second should be R, D, L or U; the third must be a number between one
and nine inclusive.

Newline is pressed, the curosr moves to a new position - right, down, left
or up by the input number of spaces - and leaves the first character behind.
When the design is finished - any combination of symbols giving a picture,
sketch, graph or map - input "S". This gives removal of the cursor, line 18,
and report code, line 19, so that only wanted material is displayed. The
design may be Saved on cassette. Line 8 is a mug trap to prevent a crash if
Newline alone is input.