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a variable whose values are used to distinguish elements of a given set. For example, the equation (x — a)2 + (y — b)2 = 1 in rectangular Cartesian coordinates determines the set of all circles of radius 1 in the xOy plane. By setting a = 3 and b = 4, we isolate in this set the completely defined circle with center at (3, 4). Thus, a and b are the parameters of a circle in the set.
in engineering, a quantity that characterizes a certain aspect of a process, phenomenon, system, or device. Examples of such quantities in mechanical systems are mass, coefficient of friction, moment of inertia, and tension. Such parameters as heat capacity, heat flow, and thermal head are used for thermal processes. Typical electrical parameters are resistance, inductance, and capacitance. The physical processes that occur in a system are describable by equations giving the relation between the variable quantities of the processes. Parameters are usually the coefficients of the equations. They can be constants, or they can be variables dependent on time or the system’s coordinates.
The parameters of a system or device can be lumped or they can be distributed in space relative to one, two, or three coordinates. A typical example of a system with distributed parameters is an electric power transmission line, in which the inductance, capacitance, and resistance (conductance) are distributed along the entire length of the line. An example of a lumped parameter is the load on a small segment of a much longer beam.
M. M. MAIZEL’
parameter(1) Any value passed to a program by the user or by another program in order to configure the program for a particular purpose. A parameter may be anything; for example, a file name, a coordinate, a range of values, a money amount or a code of some kind. Parameters may be required as in parameter-driven software (see below) or they may be optional. Parameters are often entered as a series of values following the program name when the program is loaded; for example, a DOS switch defines a parameter. In the command dir /p the /p is a parameter switch that means pause after every screenful.
(2) In programming, a value passed to a subroutine or function for processing. Programming today's graphical applications in languages such as C, C++ and Java requires knowledge of hundreds of parameters.
In the following C function, which creates the text window for the Windows version of this database, there are 11 parameters passed to the CreateWindow routine. Some of them call yet other functions for necessary information. In order to call this routine in a program, the programmer must determine the values for every parameter.
hWndText = CreateWindow ( "TextWClass", NULL, WS_CHILD|WS_BORDER|WS_VSCROLL|WS_TABSTOP, xChar*23+GetSystemMetrics(SM_CXVSCROLL)+8, yChar*4, Rect.right-Rect.left+1-xChar*23 -2*GetSystemMetrics(SM_CXVSCROLL)+5, yChar*(Lines+1)+2, hWnd, IDC_TEXTLIST, (HANDLE)hInstance, NULL );