1.2.1 System software
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what is the purpose of an operating system?
it provides an interface for the user to interact with the hardware
What are the different functions of the operating system?
• providing a platform for application software to run • providing a user interface for the user to interact with the computer in a familiar and easy way • utility programs to help maintain the computer • memory/resource management • file management • device drivers • handles interrupts
what are interrupts?
when any device requires the attention of the processor
what is multitasking?
when you have more than one program open and running at the same time
how does the computer multitask?
the processor allocates small amounts of time for each process and cycles between them
what does the operating system do during multitasking?
assigning a time slice to each task, letting it process and then moving onto the next one so quickly it appears to happen at the same time
how is data stored?
in files
what are extensions to filenames?
an added part to a filename which tells the operating system which application to load the file into
how does the operating system present files?
a logical structure of files in folders and allow the user to rename, delete, copy and move files
what is user management?
allowing multiple users to log into the same computer
what does the operating system do for user management?
retain the settings for each user recall which access rights different users have a client-server network may impose a fixed or roaming profile for a user and manage login requests to the network
what is the user interface?
the way in which you interact with the computer as a human being
what are the features of WIMP?
• windows, icons, menus, pointers • visual • intuitive • interactive • optimised for mouse and touch gesture input
why is it inefficient to move programs already loaded into RAM when there are gaps in between the programs?
• takes a lot of time to move a program as addresses and free space references need to be updated
what are pages?
fixed size sections of a program made to fit sections of memory (thought of as physical divisions)
what is paging?
the splitting of a program to fit into a given number of pages
what is the downside of paging?
it takes no account of how it splits the program this means it could split the program inefficiently
what are segments?
different sized complete sections of programs logical divisions
what is segmentation?
splitting a program into logical segments so that it fits in memory
what are some similarities of segmentation and paging?
• both allow programs to run despite insufficient memory • pages and segments are stored on disk • pages and segments are transferred into memory when needed
what are the differences of paging and segmentation?
• pages are fixed sized. Segments are different sizes • Pages are made to fit sections of memory. Segments are complete sections of programs • Pages are physical divisions. Segments are logical divisions
what is virtual memory?
when programs are swapped/switched between main memory and a space on secondary storage. This allows more programs to appear like they are open.
what is an interrupt?
a way to signal to the processor that other applications or devices require attention.
how is the FDE cycle adapted for interrupts?
• Fetch • Decode • Execute • Check for new interrupts