There are 256 characters altogether, & each one has a code between 0 & 255. There is a complete list of them in appendix A. To convert between codes & characters, there are two functions, CODE & CHR$.
CODE is applied to a string, & gives the code of the first character in the string (or 0 if the string is empty).
CHR$ is applied to a number, & gives the single character string whose code is that number.
This program prints out the entire character set.
10 LET A=0
20 PRINT CHR$ A;
30 LET A=A+1
40 IF A<256 THEN GOTO 20
At the top you can see the symbols ", £, $ and so on up to Z, which all appear on the keyboard & can be typed in when you have the
cursor. Further on, you can see the same characters, but in white on black (inverse video); these are also obtainable from the keyboard. If you press GRAPHICS (shifted 9) then the cursor will come up as 
: this means graphics mode. If you type in a symbol it will appear in its inverse video form, & this will go on until you press GRAPHICS again or NEWLINE. RUBOUT will have its usual meaning. Be careful not to lose the cursor amongst all the inverse video characters you've just typed in.When you've experimented a bit, you should still have the character set at the top; if not, then run the program again. Right at the beginning are space & ten patterns of black, white & grey blobs; further on there are eleven more. These are called the graphics symbols & are used for drawing pictures. You can enter these from the keyboard, using graphics mode (except for space, which is an ordinary symbol using the
cursor; the black square is inverse space). You use the 20 keys that have graphics symbols written on them. For instance, suppose you want the symbol 
, which is on the T key. Press GRAPHICS to get the cursor, & then press shifted T. From the previous description of the graphics mode, you would expect to get an inverse video symbol; but shifted T is normally <>, a token, & tokens have no inverses: so you get the graphics symbol instead.Here are the 22 graphics symbols.
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$
