Functions of an Operating system Flashcards
what is an Operating system ?
an O/S is a system software that manages computer hardware , software resources and provides common programs
What does the Operating system provide ?
-User interface
-Memory management
-Interrupt Handling
-Processor scheduling
What does user interface do and Memory management ?
user interface hides the complexity of the hardware from the user by providing a user interface .
Memory Management manages the allocation of RAM to the different Programs
What are the two types of Memory Management ?
Paging and Segmentation
what is paging and segmentation ?
Paging - Available memory is divided into fixed sizes.
Segmentation - Memory is divided into segments which can be different lengths.
what are interrupts ? and an ADV and Dis-ADV ?**
An interrupt is a signal that is sent from the software to the O/S
explain the process of interrupts using stack ?
When an interrupt is detected the processor stops fetching instructions and instead pushes the Current contents of its registers onto a Stack .
what is interuupt priority ?
interrupts have different priorities and will be processed in order of priority .
if a higher priority interrupt occurs whilst an interrupt is being processed, the original interrupts will be pushed onto a STACK
what are the types of Processor scheduling methods ?
Round robin
First come First serve (FCFS)
Shortest Job First
Shortest time Remaining (STR)
Name the types of operating systems ?
Multi-use
Distrubuted
Multi-tasking system
Mobile O/S
what is a mobile O/S ?
a smart phone is a computer with a multi-tasking O/S
what is a distributed O/S ?
can co-ordinate the processing of a single job across multiple computers
what is real time operating system ?
this is O/S that operates in real time , this is often used in safety crucial environments .
what is open software and closed software ?
Open source- this allows anyone to access its source code
- the software is licence but free to use
closed source - this does not allow anyone to access its source code.
-users must pay the person/ company the copyright for a license to use the software
what does processor scheduling and interrupt handling do ?
- processor scheduling allows multi-tasking and ensures a fair share of CPU time.
- interrupt handling changes what is being processed by the CPU on a priority basis.
what is a paging table ?
a paging table keeps track of the logical and physical locations of memory where each block is held in memory.
explain how it is possible for a single processor to appear to be multi-tasking?
- by using processor scheduling this allocated the use of ram which gives the illusion that it is multitasking
what is the aim of scheduling algorithms in a multi-tasking system ?
- To provide an acceptable response time to all users
- to ensure fairness on a multi-user system
what is a bytecode?
a byte code is an intermediate code between high level and machine code . A byte code interpreter translates the bytecode to machine code
what is meant by a virtual machine ?
and how does a virtual machine protect us from potential viruses ?
- software implementation emulating the behaviour of particular hardware.
- a virtual machine will pick up suspicious code(virus) found and will not pass it into the machine to be processed
what is the difference between systems software and applications software?
- system software is needed so that the system can operate and function properly whereas the application software is needed to provide the user with applications
what is the complier?
what is the assembler ?
-The compiler translates from high level language to machine code.( the whole program at once )
-assembler translates assembly language to machine code( line by line)
what is lexical analysis?
what is syntax analysis?
what is a symbol table ?
- lexical analysis is removing unnecessary white space and comments.
- syntax analysis is checking if code is against rules of language.
- A symbol table stores key words and data types .
what is BIOS ?
This stands for basic input output system
-This is responsible for loading the O/S when the computer is not on.
This bios loads the O/S from the ROM and send to RAM
what is a device driver ?
A device driver is software that will translate computer instructions to another hardware device .
e.g a laptop sending instructions to a Printer
-This is a software that tells the O/S how to communicate with a device.
what is virtual machine ?
A virtual machine is a program that has the same functionality as a physical computer e.g( Java code)
what does the utillity Software consit of:
-antivirus
-disk fragmentation
-Backup
-Compression
explain how developers could use virtual machines?
developers can use virtual machines as information/guidance to improve a system . virtual machines emulate software therefore they could use this emulation and discover any faults in order to improve .
what is the difference between a queue daa structure and a stack data structure ?
A queue is First In First Out (FIFO), whereas a stack is Last In First Out (LIFO)
explain how a system appears to be multi-tasking ?
- processor scheduling- this is allows multi-tasking and fair share of CPU time .
what does by reference mean , and passing by value?
- passing by reference means that the functions receiveds the memory location of the variable
-passing by value means that the function receives a copy of the variable
