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A-level computing - 1 > 3 system software > Flashcards

3 system software Flashcards

1
Q

What is system software?

A

System software allows control over hardware and software of the computer. The two most common types of system software is the operating system and system start up software.

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2
Q

What is application software?

A

Application software is software that allows the user to carry out a specific task, for example sending emails or making text documents.

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3
Q

The OS is responsible for…

A

Managing the computers resources. These include storage devices, input and output devices main memory and all software that is running on the computer.

When the computer boots up it will load the main part of the OS on into the RAM. This is known as the kernel

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4
Q

Memory manager

A

Responsible for splitting the ram into chunks and assigning them to different processed based on need. It is also responsible for handling virtual memory.

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5
Q

Process manager

A

Responsible for managing processes, dealing with multitasking and deciding the order in which processes should be run.

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6
Q

File manager

A

Responsible for managing the file systems of secondary storage devices.

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7
Q

What does memory management do?

A
  • allocate enough memory so that each process can run.
  • split memory up so that it can be allocated to processes(paging/segmentation).
  • ensure security so that other processes cannot access each others data.
  • allow efficient sharing of memory.
  • extend memory by using virtual memory.
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8
Q

What does the RAM contain.

A
  • the OS
  • currently running programs
  • current files and data you are working on
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9
Q

Memory addressing

A

each byte is numbered starting from 0, and this number is referred to as an address. when addressing is mentioned this usually talking about where we find data in the RAM.

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10
Q

paging

A

paging is physical segments made in the memory.
they are of a fixed size.
each process has its own private view of pages.

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11
Q

segmentation

A

segmentation allocates memory in variable size segments, this means that it can allocate places in the RAM of set size.

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12
Q

virtual memory

A

when the memory manager sees that some pages have not been used recently then it moves the blocks into virtual memory. virtual memory is a part of the hard drive where the data is stored until the data is needed or room is freed on the RAM.

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13
Q

thrashing

A

Thrashing occurs when poor choices are made and pages are continuously moved back and forth from RAM and virtual memory.
This can cause unresponsive processes.

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14
Q

interrupts

A

hardware can send signals to the CPU known as interrupts. as the CPU is carrying out the FDE cycle it checks for interrupts at the end of each cycle so then the process can be done by the CPU before continuing others.

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15
Q

common interrupts

A
  • hard drive ready for more data to save or has retrieved requested data.
  • timer interrupt has occurred.
  • key has been pressed.
  • peripheral requires more data (printers)
  • the on/off button has been pressed.
  • hardware failure or problem encountered.
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16
Q

buffers

A

a buffer is a small block of memory inside hardware devices like printers and keyboards that holds data if keys have been pressed but the CPU is not ready for them. if the buffer becomes full the motherboard warns the user with a beep.

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17
Q

interrupt service routines

A

hardware and software can trigger interrupts and these are then dealt with by calling an interrupt service routine.
When a device driver loads it will register interest in a specific interrupt so that when the interrupt occurs the code within the device driver will be executed.

18
Q

multitasking

A

multitasking is the process of swapping applications in and out of the CPU, giving the illusion that they are running at the same time.

19
Q

scheduling

A

scheduling is the term the OS uses to define how and when a process is swapped in and out of the CPU. this allows for multitasking.

20
Q

process states - only one process can be run at once on a single CPU core. what are the 3 states of a process.

A
  • running: when the process has control of the CPU
  • ready-to-run: a process that is in a queue waiting for the CPU.
  • Blocked: a process is waiting on a input or output operation (e.g.hard drive)
21
Q

Ready-to-run queue

A

Once a new application is loaded into memory, the process becomes live and is added to the ready-to run queue rather than being placed into the running state.

22
Q

Running process- in a standard single core CPU only one process will be running at one time. Running processes can…

A
  • Complete the task and close
  • be interrupted by the scheduler
  • become blocked
  • give up CPU time
23
Q

Process swapping

A

When a process is swapped out the registers are saved and a data structure known as the PROCESS CONTROL BLOCK (PCB) is created and is used to store the contents of the register.

24
Q

The PCB (process control block) will contain…

A
  • The PC (program counter) register
  • general purpose registers
  • the ACC (accumulator)
  • variables and state of the process
  • priority and process ID
25
Q

Deadlock

A

Deadlock is when a process is waiting for a system resource that is currently held by another process, and that process is held by another process. Each process has a locked resource.

26
Q

Starvation

A

Starvation is when a process never gets the chance to run or not enough CPU time to complete in a timely manner. This normally happens due to poor scheduling.

27
Q

Main goals of a scheduler:

A
  • minimise starvation of processes
  • eliminate deadlock
  • ensure high throughput of processes
  • ensure fairness for all processes
  • ensure reasonable response time
28
Q

Round robin

A

Each process is given a fixed time to run and if it is not complete in this time it is put at the back of the ready to run queue while the next process gets its time in the CPU. This continues until all processes are complete.

29
Q

Shortest job first

A

Shortest job first relies on knowledge of how long a process requires and then it puts the shortest jobs at the start of the queue and longer processes at the end.

30
Q

Shortest remaining time

A

Shortest remaining time is when the processes with the least amount of time left to complete is put at the front of the queue.

31
Q

Multi-level feedback queues

A

Multi-level feedback queues make use of three queues and prioritise processes, so processes in level 0 will always have priority of the processor.

32
Q

Hardware drivers

A

Hardware divers are software that understands how to talk directly to a given piece of hardware. Drivers are usually made by the manufacturer of the hardware.

33
Q

Single-user OS

A

Single-user OS is very common, with windows being a classic example. Only one person at a time can have access to the systems resources.

34
Q

Multiuser OS

A

OS that run on more powerful computers or servers can allow time sharing of system resources. Common example are servers as many users can connect and use resources from the server.

35
Q

Secure shell

A

Secure shell makes use of a SSH client to connect to a server through a command line interface.

36
Q

Virtual desktop infrastructure

A

Virtual desktop infrastructure(VDI) enables users to connect to the service via a Remote Desktop. When using a VDI all processing takes place on the server.

37
Q

Real-time OS

A

Real time OS must respond within a short amount of time, that could be considered immediate. Examples of real time OS include nuclear power stations and aircraft systems. This is because a decision or action would need to be made immediately so that disaster does not occur

38
Q

Embedded OS

A

Many devices contain simple processors. Such as DVD players and washing machines, so in order to run the device an OS is required.

39
Q

Distributed OS

A

Part of a distributed os’ job is to synchronise nodes and ensure timely communication of data. Each node has a small set of features known as the microkernel.

40
Q

BIOS (basic input/output system)

A
  • initialises and tests hardware by running the POST (power-on self-test)
  • selects the first boot device based on information collected in the POST
  • tried the boot loader off that device and, if successful, runs the OS.
  • moves on to the next boot device if unsuccessful. Repeats until all boot devices have been tried.
  • if no boot devices have suitable boot loaders, the system will stop.
41
Q

Virtual machines

A

.

A-level computing - 1 (6 decks)

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