is a procedural programming language and integrated development environment written by Clinton Parker for the Atari 8-bit computers.

The language, which is similar to ALGOL, compiles to high-performance code for the MOS Technology 6502 of the Atari computers.

The runtime library is stored in the cartridge; to make a standalone application requires the Action!

Parker, working with Henry Baker, had previously developed Micro-SPL, a systems programming language for the Xerox Alto.

is largely a port of Micro-SPL concepts to the Atari with changes to support the 6502 processor and the addition of an integrated fullscreen editor and debugger.

To distribute standalone applications requires a separate run-time package which was sold by OSS as the Action!

constructs were designed to map cleanly to 6502 opcodes, to provide high performance without needing complex optimizations in the one-pass compiler.

[7] For example, local variables are assigned fixed addresses in memory, instead of being allocated on a stack of activation records.

An example of a user-defined TYPE: A reserved word is any identifier or symbol that the Action!

In order to increase performance, it disables the ANTIC graphics coprocessor, preventing its DMA engine from "stealing" CPU cycles during computation.

In comparison to microcode, they claimed it would take half as long to write and 10% of the time to debug it.

OSS focused on utilities and programming languages like BASIC XL, so this was a natural fit for Action!

distribution moved from OSS to Electronic Arts, but they did little with the language and sales ended shortly after.

[15] In a 2015 interview, Parker expressed his surprise in the level of interest in the language continued to receive, suggesting it was greater than it had been in the late 1980s.

He cited the manual as the only weak point of the package, claiming it "suffers from lack of confidence, uncertain organization and a shortage of good, hard technical data.

He began the review, "This is the best thing to happen to Atari since Nolan Bushnell figured out people would play ping-pong on a TV screen."

Laporte praised the editor, noting its split-screen and cut and paste capabilities and describing it as a "complete word processing system that's very responsive."

ran about 200 times as fast as Atari BASIC, concluding that "This language is like a finely tuned racing car.

BYTE reported that the language resembled C closely enough to "routinely convert programs between the two", and approved of its pointer support.