Operating systems Flashcards
(14 cards)
What is an operating system
software that manages computer hardware and software resources. All computer programs require an operating system to function.
Provides a layer of software services which are used to interact with the hardware. Acts as a later.,
State the functions of an operating system
process management- processes run simultaneously with scheduling.
Input/output management: communicating with devices
Backing store management: ensuring data can read/write to disk drives
Memory management: ensuring programs and data can share memory and are stored correctly without interfering with each other.
Human computer interface: display information to the user and accept input.
Utilities:P software that comes with OS to help with running .
Security
Describe utility software
file management- copy, remove, rename
Compression software- compress size of files
Task managers- view processes/‘programs that are running. Check how much processor time they are taking up . Kill unresponsive processes if necessary.
Anti-virus software: needs to ve updated at least daily
Data recovery
Data conversion
Archiving
Revision/version control
Backup software
State the types of operating system
Single tasking
Batch system
Multi-programming
Multi-user/multi-access
Multi-tasking
Stand-alone
State the three modes of operation
batch processing
Real time systems- control
Real time systems-transaction processing
Describe batch processing
OS executes a series of jobs without manual intervention.
Properties:
Large number of similar tasks and jobs
Can be run with no user interaction
Can run during the night
Outline the characteristics of real time systems
support contiuous application.
Have to deal with events that can occur simultaneously and unpredictably.
Have to provide a response to an event within a specified amount of time
Some are safety critical.
Describe real time control
e.g. automatic pilot on aircraft
Inputs are processed quickly, processing needs to be fast enough to deliver output in time and adjust outputs accordingly to avoid accidents.
Describe real time transaction processing
accessing and updating tables in a database as part of a transaction that needs toe be dealt with immediately.
Operations that all have to be carried out one after the other.
E.g. purchasing a book from Amazon/supermarket system/theate booking
Describe interrupts
a signal or message from a. Device or software to the operating system, which may cause a break in the execution of the current routine because it is requesting attention.
If OS acknowledges interrupt:
Suspends the current task
Notes where to come back to
Loads and runs an appropriate handler.
Outline the types and examples of interrupts
I/O interriot
Timer interrupt
Restart interrupt
Program check interrupts
Machine check interrupts
Give examples of interrupt priority
Impending data loss, impending hardware/software failure, imminent power failure detected
Describe types of partitioning
fixed-size memory partitions
Issues: internal fragmentation. And external.
Variable sized memory partitions
Uses dynamic partitioning.
Sets the partitions during run-time according to the processor’s needs rather than setting them initially.
Describe paging
A page table splits up the available memory into blocks of memory locations of typically 4k.
Numbers of these pages used per program.
If program requires more memory than available then a wrap file is used on the disk and also split into pages.
However fixed/variable partitioning requires contiguous memory allocation, paging allows non-contiguous.
