Program state

One of the key concepts in computer programming is the idea of state , essentially a snapshot of the measure of various conditions in the system. Most programming languages require a considerable amount of state information in order to operate properly, information which is generally hidden from the programmer. For a real world example, consider a three-way light switch. Typically a switch turns on a light by moving it to the up position, but in a three-way case that may turn the light back off -- the result is based on the state of the other switch, which is likely out of view.

In fact, the state is often hidden from the computer itself as well, which normally has no idea that this piece of information encodes state, while that is temporary and will soon be discarded. This is a serious problem, as the state information needs to be shared across multiple processors in parallel processing machines. Without knowing which state is important and which isn t, most languages force the programmer to add a considerable amount of extra code to indicate which data and parts of the code are important in this respect.

In computer science, imperative programming is opposed to declarative programming. Imperative programming is a programming paradigm that describes computation in terms of a program state (computer science) and statements that change the program state.

=see also=

*Dataflow language *Imperative programming *State (computer science)