Preemptive multitasking Computer multitasking

preemptive multitasking allows computer system more reliably guarantee each process regular slice of operating time. allows system deal rapidly important external events incoming data, might require immediate attention of 1 or process. operating systems developed take advantage of these hardware capabilities , run multiple processes preemptively. preemptive multitasking implemented in pdp-6 monitor , multics in 1964, in os/360 mft in 1967, , in unix (1969, , available in operating systems computers small dec s pdp-8; core feature of unix-like operating systems, such linux, solaris , bsd derivatives, modern versions of windows.

at specific time, processes can grouped 2 categories: waiting input or output (called i/o bound ), , utilizing cpu ( cpu bound ). in primitive systems, software poll , or busywait while waiting requested input (such disk, keyboard or network input). during time, system not performing useful work. advent of interrupts , preemptive multitasking, i/o bound processes blocked , or put on hold, pending arrival of necessary data, allowing other processes utilize cpu. arrival of requested data generate interrupt, blocked processes guaranteed timely return execution.

the earliest preemptive multitasking os available home users sinclair qdos on sinclair ql, released in 1984, few people bought machine. commodore s powerful amiga, released following year, first commercially successful home computer use technology, , multimedia abilities make clear ancestor of contemporary multitasking personal computers. microsoft made preemptive multitasking core feature of flagship operating system in 1990s when developing windows nt 3.1 , windows 95. later adopted on apple macintosh mac os x that, unix-like operating system, uses preemptive multitasking native applications.

a similar model used in windows 9x , windows nt family, native 32-bit applications multitasked preemptively, , legacy 16-bit windows 3.x programs multitasked cooperatively within single process, although in nt family possible force 16-bit application run separate preemptively multitasked process. 64-bit editions of windows, both x86-64 , itanium architectures, no longer provide support legacy 16-bit applications, , provide preemptive multitasking supported applications.