Z94.12.3 H - Manufacturing Automation & Computer Control

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HANDSHAKING. (1) A descriptive term often used interchangeably with "buffering'' or "interfacing,'' implying a direct connection or machining of specific units or programs. Some computer terminal programs are called "handshaking'' if they greet and assist the new terminal operator to interface with or use the procedures or programs of the system. Other handshaking relates to direct package-to-package connections as regards circuits, programs, or procedures. (2) Exchange of predetermined signals when a connection is established between two data set devices.

HARD COPY. Any visually readable form of data output produced by a computer. For example, a printed listing, punched cards, or paper tape.

HARDWARE. The physical equipment of a system, as opposed to software; the mechanical, electrical, magnetic features of a system that are permanent components. Refers to the metallic or "hard'' components of a computer system in contrast to the ``soft'' or programming components. The components of circuits may be active, passive, or both.

HARD-WIRE LOGIC. Refers to logic designs for control or problem solutions that require interconnection of numerous integrated circuits formed or wired for specific purposes and relatively unalterable. A hard-wired diode matrix is hard-wired logic whereas a RAM, ROM, or SPU can be reprogrammed with little difficulty to change the purpose of operation. Hard-wired interconnections are usually completed by soldering or by printed circuits and are thus in contrast to software solutions achieved by programmed microcomputer components.

HARD-WIRED SYSTEM. An NC system with a fixed wired program built in when manufactured and not subject to changes by programming. Changes are possible only through altering the physical components or interconnections.

HEURISTIC METHOD. An exploratory method of problem solving in which various types of solutions that may or may not work are systematically applied and evaluated until a solution is found.

HIERARCHY. A group or series classified and arranged in rank order.

HEXADECIMAL. Refers to whole numbers in positional notation with 16 as the base. Hexadecimal uses 0 through 15, with the first ten represented by 0 through 9 and the last six digits represented by A,B,C,D,E, and F.

HIGH-LEVEL LANGUAGE. Computer language which uses readily understood symbols and command statements. Each statement typically represents a series of computer command statements. Each statement typically represents a series of computer instructions. Examples of high-level languages are BASIC, FORTRAN, and APT.

HOST COMPUTER. (1) The primary or controlling computer in a multiple operation. (2) A computer used to prepare programs for use on another computer or on another data processing system; for example, a computer used to compile, link, edit, or test programs to be used on another system.

HUNTING. Refers to a continuous attempt on the part of an automatically controlled system to seek a desired equilibrium condition. The system usually contains a standard, a method of determining deviation from this standard, and a method of influencing the system such as the difference between the standard and the state.

HYBRID COMPUTER. Various specially-designed computers with both digital and analog characteristics, combining the advantages of analog and digital computer when working as a system. Hybrid computers are being used extensively in simulation of process control systems where it is necessary to have a close representation with the physical world. The hybrid system provides good precision that can be attained with analog computers and greater control than is possible with digital computers, plus the ability to accept input data in either form.

HYSTERESIS. The difference between the response of a unit or system to an increasing signal and the response to a decreasing signal.

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