OCR a-level computer science systems software Exam 2024 Questions And Answers 100% Updated!

operating system - ANSWERSprogram or set of programs that manages the operations of the computer for the user and bridges the gap between the user and the hardware functions of operating system - ANSWERSmemory management interrupt service routines processor scheduling backup management input and output management paging - ANSWERSmemory divided into fixed sized pages of 4Kb pages held non-contiguously in memory page table maps physical locations to logical locations segmentation - ANSWERSthe logical division of programs into varying sized segments depending on program structure virtual memory - ANSWERSthe use of secondary storage as an extension of ram interrupt - ANSWERSa signal from a program, hardware device or internal clock to the cpu signalling a need for attention interrupt service routine - ANSWERSa section of code called by the CPU when an interrupt needs servicing scheduler - ANSWERSOS module that ensures processor time is used as efficiently as possible objectives of a scheduler - ANSWERSmaximise throughput be fair to all users on a multi-user system provide acceptable response time to all users ensure hardware resources are kept as busy as possible round robin - ANSWERSeach process has a specified time slice of processing time. it must either finish processing in that time or return to the back of the queue. very fair, but inefficient first come first served - ANSWERSjobs are processed in the order the arrive shortest remaining time - ANSWERSprocess with smallest estimated time to completion run first. reduces number of waiting jobs, but requires knowledge of how long jobs take to run shortest job first - ANSWERSlowest estimated run time is run next. same advantages and disadvantages as srt multi-level feedback queues - ANSWERSgives preference to short jobs and i/o bound processes and separates processes into categories based on processor needs. uses several queues and can move jobs between queues to increase efficiency and reduce bottle necking buffer - ANSWERSarea of memory to hold i/o bound data as this is slow and allows the cpu to do something else while it processes distributed os - ANSWERSparallel processing system spreading the load over multiple computer servers providing how power and performance systems that appear as one computer to the user multi-tasking os - ANSWERSoperating system capable of running or appearing to run more than one program at a time. multi-user os - ANSWERSsingle computer that hosts several dumb workstations and shares the central computer resources embedded os - ANSWERSdevice-specific os that is highly specialised and provides only the absolutely necessary functions real-time os - ANSWERSoperating system in a time-critical, safety-critical environment that responds to interrupts very fast, deals with many inputs simultaneously, is fail-safe and has backup hardware basic input output system - ANSWERSinitialises and tests system hardware, then finds