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 section}s. 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.