monitor

1. A cathode-ray tube and associated electronics connected

to a computer's video output. A monitor may be either

monochrome (black and white) or colour (RGB). Colour

monitors may show either digital colour (each of the red,

green and blue signals may be either on or off, giving eight

possible colours: black, white, red, green, blue, cyan,

magenta and yellow) or analog colour (red, green and blue

signals are continuously variable allowing any combination to

be displayed). Digital monitors are sometimes known as TTL

because the voltages on the red, green and blue inputs are

compatible with TTL logic chips.

See also gamut, multisync, visual display unit.

2. A programming language construct which encapsulates

variables, access procedures and initialisation code within an

abstract data type. The monitor's variable may only be

accessed via its access procedures and only one process may be

actively accessing the monitor at any one time. The access

procedures are critical sections. A monitor may have a

queue of processes which are waiting to access it.

3. A hardware device that measures electrical events such as

pulses or voltage levels in a digital computer.

4. To oversee a program during execution. For example, the

monitor function in the Unix C library enables profiling

of a certain range of code addresses. A histogram is produced

showing how often the program counter was found to be at

each position and how often each profiled function was called.

Unix man page: monitor(3).

5. A control program within the operating system that

manages the allocation of system resources to active

programs.

6. A program that measures software performance.