!!!Atari BASIC

!Background
Atari BASIC is the "standard" BASIC dialect for the 8-bit series. It was originally sold separately as a (relatively expensive) 8k ROM cartridge. Starting with the 1200XL, the ROMs were included inside the machine. There are three versions, the original version, retroactively known as Revision A, and the updated Revision B and C which fixed various bugs.

Atari originally licensed the 6502-assembler code for Microsoft BASIC. This came in two versions, one that was about 7900 bytes that used a 6-byte floating point number format, and another that was closer to 9000 that included an expanded floating point format with 9-byte numbers. The vast majority of 8-bit machines used the larger 9k version, and then further expanded it with additional functions for basic input/output. For instance, the BASIC and I/O in the early PET machines was supplied in a total of 12k of ROM.

Atari had selected an 8k cartridge format because that was an easy size to supply in a single ROM. So the Atari programmers started with the smaller 8k version of the MS code and struggled to cut it down enough to fit in a cart. That was hard enough of its own, but they really wanted to add additional instructions to take advantage of the Atari's graphics and sound. Eventually, some time in the summer of 1978, they gave up and went looking for a 3rd party to do it for them.

Shepardson Microsystems Inc, or SMI for short, won the contract. They proposed a simplified syntax and the cutting of a number of rarely-used features, leaving more room for new commands for graphics and sound. Even then, the result required about 10k, so to cross the remaining gap to 8k, some of the core libraries were moved out of the language and into the operating system ROMs. This had the side-effect of allowing any other language on the Atari to use these routines as well.

By the time SMI was hired, Atari was in something of a rush to get a working BASIC. They were planning to show the machines in January 1979, using the working MS version, but then sell the machines later that year with the SMI version instead. The original contract required SMI to make its final delivery in April 1979, but it contained bonus clauses if they finished early. They did: a working version was delivered in October 1978, so Atari to that to CES instead. To SMI's surprise, they learned that Atari had begun burning that version to ROM for sale, even though it had several known bugs. SMI offered an updated version with various fixes, but Atari didn't bother using it, and instead shipped the buggy version for years.

Two major pieces of code were moved out of the BASIC into the OS ROM. The first was a set of graphics routines to set up the screen, draw lines, and similar. The second was the floating point math system, based on a new implementation of the 6-byte binary-coded-decimal (BCD) format. Both libraries were notoriously slow. Generally, Atari BASIC was among the slowest BASICs of its era, both due to the OS code and two problems involving loops. 

The performance issues led to a profusion of 3rd party BASICs, some of which continue to be developed to this day. By replacing the math libraries and fixing these two loop issues, speed improves on the order of 3 to 5 times in most programs, and this is a common feature of 3rd party BASICs like [TURBO-BASIC XL] and [Altirra Basic]. For even higher performance, [FastBasic] uses a p-code system that can be quickly interpreted.

!Design notes
Atari BASIC has some key differences with the more common MS-derived BASICs found on most contemporary machines. This included the 6-byte vs. 9-byte math, but also included numerous syntax changes as well. Generally, one can describe Atari BASIC's design philosophy as "modeless" and "orthogonal".

Most BASICs of the era had the concept of "immediate mode" and "program mode", and some commands could only be used in one more or the other. A good example in MS BASIC is the {{LIST}} command, which could only be used in immediate mode, at the "command line". Atari BASIC removed this limitation, one could write a program containing {{10 LIST}}.

Additionally, most BASICs had commands that read input or produced output, for example, the {{INPUT}} can be thought of as the opposite of {{PRINT}}. Atari BASIC was orthogonal in that every such command had a partner. For instance, {{LIST}} produces output, so the new command {{ENTER}} reversed this, reading a program listing from a device. This opened up a number of possible overlay techniques that other BASICs lacked.

The most noticable difference between Atari BASIC and MS-derived versions is the string handling. Atari BASIC used a greatly simplified system of character-arrays instead of the dynamic strings in MS. This meant that all strings had to be predefined using {{DIM}}, and their length could not be changed during run-time. There are a number of advantages to this approach, notably speed, but memory handling is more difficult and conversion of standard programs from MS listings is more difficult.

!What's missing
In addition to differences like string handling, Atari BASIC also lacked some of the less-used features found in MS BASIC. Among these are...

* {{TAB}} and {{SPC}}, for formatting output
* {{PRINT USING}}, which formatted output
* {{INPUT "prompt", A$}}, which printed the prompt and placed the cursor at the end
* {{DEF FN}}, which defines mathematical functions

Most 3rd party BASICs add many of these features, and more.

!What's new
To allow BASIC programmers access to the advanced features of the system, Atari BASIC added commands for defining the GRAPHICS, changing COLORs, MOVEing and drawing a LINETO, playing SOUND, and others.

!! Manuals

* [The Atari BASIC source book|The Atari Basic Source Book], contains the complete source code for Atari BASIC, fully described. Useful for anyone interested in interpreter design.
* [Atari Basic Rev C Reference Manual]
* [ATARI Basic Leitfaden.pdf]
* [Atari BASIC Quick Reference Guide-Gilbert Held.pdf]
* [ATARI BASIC-Handbuch für Selbststudium und Praxis-BOB ALBRECHT, Le Roy Finkel, JERALD BROWN-Screen.pdf] 214 Doppelseiten, OCR, 44,8 MB
* [Monkey_Wrench_-_Manual.pdf] ; size: 67.5 MB ; thanks to [serious computerist|http://seriouscomputerist.altervista.org/pages/utility/utility.atari.htm], we really appreciate! :-)
* [Monkey_Wrench_II_-_Manual.pdf] ; size: 2.5 MB ; thanks to [serious computerist|http://seriouscomputerist.altervista.org/pages/utility/utility.atari.htm], we really appreciate! :-)
* [The major differences between the Monkey Wrench II and Monkey Wrench II-XL cartridges|Monkey_Wrench_II_XL_-_Notes.rtf] ; thanks to [serious computerist|http://seriouscomputerist.altervista.org/pages/utility/utility.atari.htm], we really appreciate! :-)

!! CAR-Images

* [Atari_Basic_Rev._A.car] ; ? PEEK(43234) should return: 162
* [Atari_Basic_Rev._B.car] ; ? PEEK(43234) should return: 96
* [Atari_Basic_Rev._C.car] ; ? PEEK(43234) should return: 234
* [The Monkey Wrench.car] Tool for better editing Basic programs, version I
* [The Monkey Wrench II.car] Tool for better editing Basic programs, version II v2
* [Monkey_Wrench_with_BASIC_(Rev._C).car] ; both cartridges in just one 16 KiB file
* [Monkey_Wrench_II_OS-B_right_v1.car] ; thanks to [serious computerist|http://seriouscomputerist.altervista.org/pages/utility/utility.atari.htm], we really appreciate! :-)
* [Monkey_Wrench_II_OS-B_right_v2.car] ; thanks to [serious computerist|http://seriouscomputerist.altervista.org/pages/utility/utility.atari.htm], we really appreciate! :-)
* [Monkey_Wrench_II_XL_with_BASIC_(Rev._C).car] ; both cartridges in just one 16 KiB file

!! ROM-Images

* [Atari Basic Rev. A.rom] ; ? PEEK(43234) should return: 162
* [Atari Basic Rev. B.rom] ; ? PEEK(43234) should return: 96
* [Atari Basic Rev. C.rom] ; ? PEEK(43234) should return: 234
* [Monkey_Wrench_with_BASIC_(Rev._C).rom] ; both roms in just one 16 KiB file
* [Monkey_Wrench_II_OS-B_right_v1.rom] ; thanks to [serious computerist|http://seriouscomputerist.altervista.org/pages/utility/utility.atari.htm], we really appreciate! :-)
* [Monkey_Wrench_II_OS-B_right_v2.rom] ; thanks to [serious computerist|http://seriouscomputerist.altervista.org/pages/utility/utility.atari.htm], we really appreciate! :-)
* [Monkey_Wrench_II_XL_with_BASIC_(Rev._C).rom] ; both roms in just one 16 KiB file

To create one 16 KiB-ROM out of 2 8 KiB ROMs, use the following method:

__Windows:__
Go to the CMD shell and there to the directory, where the 2 files are, which should be combined, then type:\\
\\
copy /b monkey.rom+basic.rom allinone16k.rom\\
\\
and the resulting rom file can be found in the same directory. Done. :-)\\

__Mac:__
Start application Terminal and then type cd and a blank. Drag the folder, in which the 2 files are directly behind the blank. Check with typing ls -a, whether the 2 files can be seen. Then type:\\
\\
cat monkey.rom basic.rom > allinone16k.rom\\
\\
and the resulting rom file can be found in the same directory. Done. :-)\\

!! Atari Basic Course: An Invitation to Programming 1-3

* [An Invitation to Programming 1 CX4101]
* [An Invitation to Programming 2 CX4106]
* [An Invitation to Programming 3 CX4117]

!! Kurs 1: Programmieren leicht gemacht-Lernen Sie BASIC mit Dagmar Berghoff-TXG4110

* [Programmieren leicht gemacht TXG4110]

!! Kurs 2: Noch mehr BASIC-Lernen Sie BASIC mit Dagmar Berghoff-RXG 55007

* [Noch mehr BASIC RXG 55007]

!! Kurs 3: BASIC für Fortgeschrittene-Lernen Sie BASIC mit Dagmar Berghoff

* [BASIC für Fortgeschrittene]

!! Source and Tools

* [Atari BASIC Article in Wikipedia|http://en.wikipedia.org/wiki/ATARI_BASIC]
* [Atari Basic vs. Commodore C64 Basic vs. Apple II Basic]
* [Atari BASIC: the good, the bad and the ugly|http://archive.li/njp7N]
* [RPM810] Program to measure 810 disk speed
* [Infoline] Infoline for BASIC and ACTION!
* [ST Mouse Driver for Basic]
* [Boolean Logic in BASIC]
* [Atari Basic Special Clear Screen] (german)
* [How to find the revision number of Atari Basic]
* [Basic Fast Stack and Fast Jump]
* [BASIC on-off from DOS XL commandline]
* [Page Flip Routine for Basic]
* [RAM Move Routine for Basic]
* [Basic Program Lister]
* [UUDecoder]
* [Create Data-Statements from binary load files]
* [Schnelle Player Bewegung in Basic] (german)
* [REV.B TO REV.C CONVERTER.txt] Atari Basic Rev. B to Rev. C Converter as TXT file
* [RevB2C.atr] Atari Basic Rev. B to Rev. C Converter as ATR-image