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Summary OCR Computer Science A-Level notes on Functions of an Operating System
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Summary notes for OCR Computer Science A-Level on Functions of an Operating System
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System Software comes in many types, e.g: OS, Utility Programs and Program translators.OS= manage hardware, users and resources which are used by software,
They are responsible for:
The UI
Memory management
Multitasking
Peripheral Management + drivers
User Management
File Management
User interface often have differences between desktops and tablets/smartphones. E.g. phones= no
pointers; can't be seen under finger and windows for apps generally take up the whole screen.
A common acronym for GUIs is WIMP= Windows, Icons, Menus and Pointers.
There are also other interfaces such as: Menu-driven, Command Line Interface, Voice Activated and Real
Time (sensors detecting inputs).
Command Line Interfaces (CLI): Text commands entered into computer- little processing + save on need for
expensive graphics card.
Memory Management:
Programs + data need to be loaded into RAM.
OS must manage allocation of RAM to different programs.
Chance of not sufficient RAM for all desired processes to be completely loaded into RAM at once.
Paging:
Available memory divided into fixed chunks called pages- each page has an address.
Pages are made to fit sections of memory, programs are split up to fit into a given number of pages.
A process can be loaded into RAM and is allocated sufficient pages, but those pages may not be contiguous
(next to each other) in physical terms.
A page table maps between the logical memory locations and physical memory locations.
Segmentation:
Alternatively, memory is divided into segments which can be of different lengths. Segments relate to parts
of program e.g. a function, or sub routine may take up one segment.
Virtual Memory:
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