GETTING STARTEDGETTING STARTEDGETTING STARTED

01LINE NUMBERS MEAN PROGRAM

If you type something without a line number it happens immediately. Type the same thing with a line number and it is put away for later, and only runs when you type RUN.

PRINT 2+2        → answers 4 right away
10 PRINT 2+2     → silent; saved as line 10

The numbers do not have to follow each other. Count in tens — 10, 20, 30 — and you leave room to squeeze a line in between later.

02SEE IT, CHANGE IT, DELETE IT

• LIST shows the program as it looks right now.
• Type a line with the same number again and it is replaced.
• Type just the number and Enter and the line disappears.
• NEW empties the whole machine.

03REMEMBERING THINGS

A variable is a box with a name. Names ending in $ hold text, the rest hold numbers.

10 A=5
20 B$="CAT"
30 PRINT A;" ";B$

Only the first two letters of the name count — COUNT and COUSIN are the same box. That was true on the real machine too.

04DOING IT AGAIN AND AGAIN

10 FOR I=1 TO 5
20 PRINT I
30 NEXT I

To jump several steps at a time, add STEP: FOR I=0 TO 10 STEP 2.

05CHOOSING A PATH

10 A=7
20 IF A>5 THEN PRINT "BIG"
30 IF A<=5 THEN PRINT "SMALL"

GOTO jumps to a line number, and GOSUB jumps there and comes back when the line RETURN is reached.

06ASKING WHOEVER IS WATCHING

10 INPUT "WHAT IS YOUR NAME";N$
20 PRINT "HELLO ";N$

The program stops and waits for an answer. Type and press Enter.

07CHANGING COLOURS FOR REAL

Three addresses in the machine's memory control the colours, and they work here exactly as they did in 1982. The number is 0–15.

POKE 53280,5     the border
POKE 53281,0     the background
POKE 646,7       the text from here on

PEEK is the way back: it reads an address instead of writing to it. PRINT PEEK(646) answers with the colour you just set. Address 162 is the machine's clock and counts up sixty times a second all by itself:

10 PRINT PEEK(162)
20 GOTO 10

POKEd yourself into something unreadable? COLOR on the front page resets the screen.

08READING THE KEYBOARD WHILE THE PROGRAM RUNS

INPUT stops the program and waits. If you would rather read keys while it keeps going — the way a game does — the queue sits at address 198. It holds the number of keys pressed, and the characters themselves from 631 onwards.

10 IF PEEK(198)=0 THEN 10
20 PRINT CHR$(PEEK(631));
30 POKE 198,0
40 GOTO 10

Line 10 spins until someone presses something. Line 20 prints the character, and POKE 198,0 on line 30 empties the queue so the next key shows up. You have built a typewriter.

The program never stops on its own — press STOP on the front page to break it.

09SAVING WHAT YOU WROTE

What you type lives only in the browser's memory and is otherwise lost when you reload the page.

SAVE "MINE"      save
DIR              see what is there
LOAD "MINE"      fetch it back
SCRATCH "MINE"   delete

The programs are saved in your own browser, not on the server. They do not travel to another computer, and they disappear if you clear the browser's data.

10LOOK AT A FINISHED ONE

On the disk there is a small program to start from. Load it, read the code and change it — it will not break.

LOAD "DEMO"
LIST
RUN

11WHEN SOMETHING GOES WRONG

?SYNTAX ERROR means the machine did not understand the line. Look for a missing quotation mark or a comma in the wrong place, and type the line again.

If you have written an endless loop, break it with Escape. The machine then tells you which line it was on.

HELP on the front page lists everything you can type.