Variable Assembly Language: Difference between revisions

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{{single source|date=July 2025}}

'''Variable AssemblyAlgorithmic Language''' ('''VAL''') is a [[computer]]-based [[control system]] and language designed specifically for use with [[Unimation|Unimation Inc.]] industrial robots.

The VAL [[robot]] language is permanently stored as a part of the VAL system. This includes the programming language used to direct the system for individual applications. The VAL language has an easy to understand syntax. It uses a clear, concise, and generally self-explanatory [[instruction set]]. All commands and communications with the robot consist of easy to understand word and number sequences. Control programs are written on the same computer that controls the robot. As a [[real-time computing|real-time]] system, VAL's continuous [[trajectory]] computation permits complex motions to be executed quickly, with efficient use of system memory and reduction in overall system complexity. The VAL system continuously generates robot control commands, and can simultaneously interact with a human operator, permitting on-line program generation and modification.

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==VAL programming==

Several conventions apply to numerical values to be supplied to VAL commands and instructions. Preceding each monitor-command description are two symbols indicating when the command can be typed by the user. A dot (.) signifies the command can be performed when VAL is in its top-level [[monitor mode]] and no user program being executed (that is, when the system prompt is a dot). An asterisk (*) indicates the command can be performed at the same time VAL is executing the program (that is, when the system prompt is an asterisk). If both symbols are present the command can be executed in either case. Most monitor commands and program instructions can be abbreviated. When entering any monitor command or program instruction, the function name can be abbreviated to as many characters as are necessary to make the name unique.

For commands and instructions, angle brackets, < >, are used to enclose an item which describes the actual argument to appear. Thus the programmer can supply the appropriate item in that position when entering the command or instruction. Note that these brackets used here are for clarification, and are never to be included as part of a command or instruction.

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* the top level is called the VAL operating system, or monitor, because it administers operations of the system, including interaction with the user;

* the second level is used for diagnostic work on the controller hardware. The system monitor is a computer program stored VAL programmable read-only memory ([[Programmable read-only memory|PROM]]) in the Computer/Controller.

PROM memory retains its contents finitely, and thus VAL is immediately available when the controller is switched on. The monitor is responsible for control of the robot, and its commands come from the manual control unit, the system terminal, or from programs. To increase its versatility and flexibility, the VAL monitor can perform of its commands even while a user program is being executed. Commands that can be processed in this way include those for controlling the status of the system, defining robot locations, storing and retrieving information on the [[floppy disk]], and creating and editing robot control programs.

==References==