Action! (programming language)
|Original author(s)||Clinton Parker|
|Developer(s)||Optimized Systems Software|
v3.6 / 1983
|Platform||Atari 8-bit family|
|Size||16K bank-switched cartridge|
Action! is a procedural programming language similar to ALGOL 68 that is intended to produce high-performance programs for the Atari 8-bit family. The language was written by Clinton Parker and distributed on ROM cartridge by Optimized Systems Software starting in 1983.
Action! was used to develop at least two commercial products—the Homepak productivity suite and Games Computers Play client program—and numerous programs in ANALOG Computing and Antic magazines. The system was not ported to any other platforms.
Parker had previously developed Micro-SPL with Henry Baker, a similar programming language for the Xerox Alto. The 6502 assembly language source code for Action! was made available under the GNU General Public License by the author in 2015.
Action! consists of the editor, the compiler, a monitor for testing code and switching between the editor and compiler, and the run-time library. The run-time library is stored in the cartridge itself. To distribute standalone applications requires a separate run-time package which was sold by OSS as the Action! Toolkit.
Action! constructs were designed to map cleanly to 6502 opcodes, to provide high performance without needing complex optimizations in the one-pass compiler. For example, local variables are assigned fixed addresses in memory, instead of being allocated on the stack. This enables tight code for the 6502, but precludes the use of recursion.
Unlike the integrated Atari BASIC and Atari Assembler Editor environments, the Action! editor is full-screen, so it does not use line numbers. It features a full-screen, scrolling display capable of displaying two windows, as well as block operations and global search and replace.
The monitor serves as a debugger, allowing an entire program or individual functions to be run, memory to be displayed and modified, and program execution to be traced.
Action! has three fundamental data types, all of which are numeric.
BYTE age= ; declare age and initialize it to the value 21 BYTE leftMargin=82 ; declare leftMargin and store it at address 82
CARD population=$600 ; declare population and store it at address 1536 and 1537 CARD prevYear, curYear, nextYear ; use commas to declare multiple variables
INT veryCold = [-10] INT profitsQ1, profitsQ2, ; declaring multiple variables can profitsQ3, profitsQ4 ; span across multiple lines
Action! also has ARRAYs, POINTERs and user-defined TYPEs. No floating point support is provided.
An example of a user-defined TYPE:
TYPE CORD=[CARD x,y] CORD point point.x=42 point.y=23
A reserved word is any identifier or symbol that the Action! compiler recognizes as something special. It can be an operator, a data type name, a statement, or a compiler directive.
AND FI OR UNTIL = ( ARRAY FOR POINTER WHILE <> ) BYTE FUNC PROC XOR # . CARD IF RETURN + > [ CHAR INCLUDE RSH - >= ] DEFINE INT SET * < " DO LSH STEP / <= ' ELSE MOD THEN & $ ; ELSEIF MODULE TO % ^ EXIT OD TYPE ! @
The following is example code for Sieve of Eratosthenes written in Action!. In order to increase performance, it disables the ANTIC graphics co-processor, preventing its DMA engine from "stealing" CPU cycles during computation.
BYTE RTCLOK=20, ; addr of sys timer SDMCTL=559 ; DMA control BYTE ARRAY FLAGS(8190) CARD COUNT,I,K,PRIME,TIME PROC SIEVE() SDMCTL=0 ; shut off Antic RTCLOK=0 ; reset the clock to zero COUNT=0 ; init count FOR I=0 TO 8190 ; and flags DO FLAGS(I)='T ; "'T" is a compiler-provided constant for True OD FOR I=0 TO 8190 ; and flags DO IF FLAGS(I)='T THEN PRIME=I+I+3 K=I+PRIME WHILE K<=8190 DO FLAGS(K)='F ; "'F" is a compiler-provided constant for False K==+PRIME OD COUNT==+1 FI OD TIME=RTCLOK ; get timer reading SDMCTL=34 ; restore screen PRINTF("%E %U PRIMES IN",COUNT) PRINTF("%E %U JIFFIES",TIME) RETURN
Brian Moriarty, in a February 1984 review for ANALOG Computing, cited the manual as the weak point of the package: "[it] suffers from lack of confidence, uncertain organization and a shortage of good, hard technical data." He concluded by calling Action! "one of the most valuable development tools ever published for the Atari."
BYTE in 1985 praised the compilation and execution speed of software written in Action!—ten iterations of the Sieve of Eratosthenes ran in less than 18 seconds, compared to 10 seconds for assembly and 38 minutes in BASIC—and its editor. The magazine reported that the language resembled C closely enough to "routinely convert programs between the two", and approved of its pointer support. BYTE concluded that "Action! is easy to use, quick, and efficient. It can exploit the Atari's full power. Action! puts programming for the Atari in a whole new dimension."
- PaperClip - Atari 8-bit word processor from a different author and company, but based on the Action! editor.
- Clinton Parker, Action!, ANTIC Interview 111, 31 December 2015, hosts: Randy Kindig, Kevin Savetz, Brad Arnold, ANTIC The Atari 8-bit Podcast
- Baker, Henry; Parker, Clinton. "Micro SPL". CiteSeerX 10.1.1.126.6877.
- Action! Source Code - Page 2, Alfred (Chopper Commander) Posted Mon Feb 2, 2015 1:38 PM, AtariAge Forums, This is the original Action! source as I received it from ICD. It uses the ICD cross assembler which is not included in the zip. It can be easily converted to other formats
- Moriarty, Brian. "Review - Action!". ANALOG Computing (16).
- ACTION! in Atariki (PL)
- Schneeflock, Ed (March 1985). "Action! A Poor Man's C?". BYTE. p. 273. Retrieved 19 March 2016.
- Chadwick, Ian (1985). "Author's Preface To The Revised Edition". Mapping the Atari. Greensboro, North Carolina: Compute! Publications, Inc. pp. v–vi. ISBN 0-87455-004-1.