Saving your work

Your program lives in memory, and memory forgets when the power goes. The CompactFlash card in the side of the ACE doesn't.

Storage covers the card itself — how it's divided into 256 disks of a megabyte each, and what DISK and FORMAT do. This chapter is about using it from a program.

Save and load

SAVE "GAME"

OK

NEW
LOAD "GAME"
RUN

SAVE writes whatever is in memory, LOAD reads it back — replacing whatever was there, so LOAD is a NEW you didn't ask for. DIR lists what's on the current disk:

DIR
DISK 0
HELLO   .TXT 6
GAME    .    24

Names are up to eight characters, with an optional three-character extension after a dot, and the listing pads them out into those columns. The number on the end is the size in bytes.

DEL "GAME" removes one.

Saving from inside a program

All of these work in a program as well as at the prompt, which means a program can manage its own files:

10 PRINT "FILES ON THIS DISK"
20 PRINT
30 DIR
40 PRINT
50 PRINT "TYPE A NAME TO LOAD IT, OR JUST ENTER";
60 INPUT F$
70 IF F$ = "" THEN PRINT "NOTHING LOADED" : END
80 LOAD F$

RUN
FILES ON THIS DISK

DISK 0
HELLO   .TXT 6

TYPE A NAME TO LOAD IT, OR JUST ENTER?
NOTHING LOADED

OK

Note what happens if you do type a name: LOAD replaces the running program with the loaded one and starts it. That's a menu program in six lines — and it's also why you can't do anything after the LOAD, because there is no "after" any more.

Saving data rather than programs

SAVE and LOAD deal in programs. For raw bytes — a high score, a level, a screenful of something — use BSAVE and BLOAD:

BSAVE address, length, "name"	write length bytes starting at address
BLOAD address, "name"	read a file back into memory at address

10 POKE 2560, 42
20 BSAVE 2560, 1, "SCORE.DAT"
30 POKE 2560, 0
40 BLOAD 2560, "SCORE.DAT"
50 PRINT "HIGH SCORE IS"; PEEK(2560)

RUN
HIGH SCORE IS 42

OK

Line 10 puts a value somewhere safe, line 20 writes that one byte to the card, line 30 proves it's really gone from memory, and line 40 brings it back.

Address 2560 is in the free space above where BASIC keeps programs, which makes it a reasonable scratch address for a small program. For anything bigger, see what BASIC does with your memory before you pick an address — writing over your own program is a memorable way to spend an evening.

Over the serial port instead

SAVE and LOAD with no filename don't touch the card at all — they send and receive over the serial port using XModem, which is how you get a program on or off a laptop:

SAVE

Serial and a terminal has the settings and the terminal side of it.

Which disk

Files live on the current disk, and DISK n changes it:

DISK 3
DIR

A fresh disk has nothing on it and DIR shows nothing. MEM reminds you which one you're on if you've lost track.

Save early

There's no autosave and no undo. SAVE "WORK" every so often while you're typing something long costs three seconds. Retyping ninety lines costs an evening.

Next: the clock, and the memory that survives being switched off.