Apple BASIC, Huston version

Also referred to as Integer BASIC. Sold by Apple Computer on cassette tape for $5, order code A1T001X.

History

At the time, BASIC was a very popular language that enabled people to do more stuff with their mini- and microcomputers more easily. In order for the Apple-1 to succeed it needed a BASIC.

Apple BASIC was written by Steve Wozniak himself and later on improved further by other people. It did not support floating point arithmetic, so no decimals could be used. It was open source and was shared amoung fellow hobbyists.

Instructions

The Preliminary Apple BASIC Users Manual explains how BASIC is loaded from cassette tape:

Hit the CLEAR SCREEN button which will clear the screen and display only the cursor (a flashing @ sign) in the upper left corner of the screen.

Hit the RESET button which will cause the computer to print a backslash (\) and move the cursor down a line.

Place the BASIC cassette into the recorder, rewinding it if necessary.

1. Type C100R RETURN
2. Type E000.EFFFR (don't hit RETURN yet!)
3. Start the tape
4. Hit RETURN
5. When BASIC is loaded (about 30 seconds) the computer will print a backslash (\).

To enter BASIC type E000R RETURN. The computer will print a few characters, then, on the next line, print the prompt character >. This prompt character (>) is used throughout BASIC to signify that the BASIC is ready for additional commands or statements.

To exit BASIC hit the RESET button. This will return control to the monitor. To re-enter BASIC from the monitor without losing the previous program, enter BASIC at E2B3 RETURN, instead of EOOO RETURN. This is extremely useful when you have unintentionally hit the RESET button while in BASIC. Normally, you should enter BASIC at E000 RETURN, which clears any previous programs.

The various BASIC statements and control structures are explained further by the manual.

Versions

Several versions are known to exist. Wendell Sander did some research into this:

There were many versions of Apple 1 Basic provided by Apple in the early days. There was just Woz and SJ and Woz was writing Basic while the computers were being sold. When someone got a copy from SJ it was just the last stable version from Woz.

I bought my Apple 1 at a Byte Shop in mid 1976 and I got 4 different versions of Basic over the next 6 months or so. I labeled them version A through D. Version A did not even have an INPUT statement so about all you could do is print HELLO WORLD. Version B added the INPUT statement, Version C added Arrays and Version D added PEEK and POKE. I have copies of C and D but have not been able to find any earlier. The Huston brothers got a copy of Apple 1 Basic in late 1977 or early 1978 when they were employees at Apple that includes a checksum program and I presume that was the last version. By late 1976 and early 1977 Woz was focused on the Apple II.

Based on the above, together with a blog article and another topic, the following comparison can be made;

¹ This version of BASIC is used for the Replica 1 and is basically the same thing as the Pagetable version, except that the DSP alias D0F2 used in the Pagetable and original Apple versions (at E3D6 and E3DB) has been replaced with D012.

In the later versions of BASIC there are traces of Apple ][ commands, as becomes clear by reading letters from Larry Nelson written in 1980 and 1981. So this is clearly proof that the development of the Apple ][ got intertwined with the Apple-1. Quoting:

Also found USR, RNDX, and OFF statements on commands in there. USR and RNDX don't work, but OFF turns off the auto-line #. (Try it by typing AUTO 10 RETURN). Then type ESC, then OFF RETURN. We have COLOR=, PLOT, HLIN, too. It adds up to 120 bytes in there + several commands that we can't use.

Maybe Woz has the early versions still lying around, who knows?

Example program

The following program can be entered while running BASIC. It displays the fibonacci numbers and can be started with the RUN command. Use LIST to check if the program is entered correctly.

05 REM Fibonacci numbers 
10 LET M = 5000
20 LET X = 1 : LET Y = 1
30 IF (X>M) THEN GOTO 100
40 PRINT X
50 X = X + Y
60 IF (Y>M) THEN GOTO 100
70 PRINT Y
80 Y = X + Y
90 GOTO 30
100 END

Memory structure of BASIC programs

In this post Larry Nelson explains how a BASIC program is organized in memory:

In the years since I last used my Apple-1, I'm not sure I remember the storage points of each program. If I gave you the wrong loading instructions it would account for the problem of not being able to load a tape. Try this: On a BASIC program that won't load, just load the first segment; 4A.00FFR. If it loads and the computer returns to the monitor, the tape can be read. Now look at the memory locations 004A, 004B, 004C, and 004D.

004B is high byte of the starting address of the second segment on the tape. 004A is the low byte of that address.

004D and 004C respectively form high and low bytes of the ending address of the 2nd segment, plus 0001h. If the 004D,004C combination is <1000h> then the ending address would be 0FFFh (1000-0001=FFFF hex). Replace the addresses you have been using with the calculated addresses and see if you can load the program. If that works, WRITE IT DOWN! If not, the problem may be with the recording itself.

For example, after a BASIC program is loaded, hit RESET to return to Wozmon. Enter 4A.4D and get the starting and ending address of the loaded BASIC program:

004A: 80 02 00 10

In this example the BASIC program is stored in memory from 0280 to 0FFF (1000 minus 0001 hex).

References

• Preliminary Apple BASIC Users Manual as provided by Apple Computer.
• Personal website by Wendell Sander explaining the differences between versions of Apple BASIC.
• Byte code comparison of the versions by Wendell Sander.
• Pagetable blog article by Michael Steil about the reconstruction of Apple 1 BASIC from a cassette tape. Referred to as the Pagetable BASIC version.
• History of an early BASIC patch, a topic by Colin Howell on Applefritter.
• Tips for loading BASIC by Larry Nelson on Applefritter.
• Two letters from Larry Nelson, written in 1980 and 1981.
• Replica-1 explained on Wikipedia.