Now look at the character set again. The tokens stand out quite clearly in two blocks: a small group of
three (
RND
,
INKEY$
&
PI
) after Z, & a larger group (starting with the quote image after , & carrying on
from
AT
up to
COPY
).
The rest of the characters all seem to be ? This is actually just the way they get printed - the real
question mark is between : and (. Of the spurious ones, some are for control characters like ,
EDIT
&
NEWLINE
, & the rest are for characters that have no special meaning for the ZX81 at all.
Summary
Functions:
CODE
,
CHR$
Exercises
1. Imagine the space for one key symbol divided up into four quaters: . Then if each quater can be either
black or white, there are 2*2*2*2 = 16 possibilities. Find them all in the character set.
2. Imagine the space for one symbol divided into two horizontally: . Then if each half can be black, white
or grey, there are 3*3 = 9 possibilities. Find them all.
3. The characters in exercise 2 are designed to be used in horizontal bar charts, using two colours, grey &
black. Write a program that inputs two numbers A & B (both between 0 & 32), & draws a bar chart for them:
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