History
See also: History of operating systemsBy the early 1960s computer control software had evolved from Monitor control software, e.g., IBSYS, to Executive control software. Computers got "faster" and computer time was still neither "cheap" nor fully used. It made multiprogramming possible and necessary.
Multiprogramming means that several programs run "at the same time" (concurrently, including parallel and non-parallel). At first they ran on a single processor (i.e., uniprocessor) and shared scarce resources. Multiprogramming is also basic form of multiprocessing, a much broader term.
Programs consist of sequences of instructions for processors. A single processor can run only one instruction at a time: it is impossible to run more programs at the same time. A program might need some resource (input ...) which has a large delay, or a program might start some slow operation (output to printer ...). This would lead to processor being "idle" (unused). To use processor at all times, the execution of such a program is halted. At that point, a second (or nth) program is started or restarted. To the user, it will appear that the programs run at the same time (hence the term, concurrent).
Shortly thereafter, the notion of a 'program' was expanded to the notion of an 'executing program and its context'. The concept of a process was born.
This became necessary with the invention of re-entrant code.
Threads came somewhat later. However, with the advent of time-sharing; computer networks; multiple-CPU, shared memory computers; etc., the old "multiprogramming" gave way to true multitasking, multiprocessing and, later, multithreading.
Read more about this topic: Process (computing)
Famous quotes containing the word history:
“We aspire to be something more than stupid and timid chattels, pretending to read history and our Bibles, but desecrating every house and every day we breathe in.”
—Henry David Thoreau (1817–1862)
“The foregoing generations beheld God and nature face to face; we, through their eyes. Why should not we also enjoy an original relation to the universe? Why should not we have a poetry and philosophy of insight and not of tradition, and a religion by revelation to us, and not the history of theirs?”
—Ralph Waldo Emerson (1803–1882)
“Whenever we read the obscene stories, the voluptuous debaucheries, the cruel and torturous executions, the unrelenting vindictiveness, with which more than half the Bible is filled, it would be more consistent that we called it the word of a demon than the Word of God. It is a history of wickedness that has served to corrupt and brutalize mankind.”
—Thomas Paine (1737–1809)