1.2.1 Systems Software

  • Created by: Zruixx
  • Created on: 23-03-23 11:37
What is an Operating System?
An Operating System is an essential piece of software that is loaded when a computer boots up.
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What is the purpose of the OS?
The OS controls the hardware within a computer by using “Managers” and also provides a API (Application Programming Interface).
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What is the API?
The Application Programming Interface is a set of code libraries that software developers can use to write applications for that operating system
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What are the 5 Managers?
1. Memory Manager
2. Process Manager
3. Device Manager
4. File Manager
5. Network Manager
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What are Distributed Operating Systems?
Distributed Operating Systems run across multiple devices, allowing the load to be spread across multiple computer processors when a task is run.
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What are Embedded Operating Systems?
Built to perform a small range of specific tasks, this operating system is catered towards a specific device. They are limited in their functionality and hard to update although they consume significantly less.
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What are Multi-tasking Operating Systems?
Multi-tasking operating systems enable the user to carry out task seemingly simultaneously. This is done by using time slicing to switch quickly between programs and applications in memory.
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What are Multi-User Operating Systems?
Multiple Users make use of one computer, typically a supercomputer, within a multi-user system. Therefore a scheduling algorithm must be used to ensure processor time is shared fairly between jobs.
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What are Real Time Operating Systems?
Commonly used in time-critical computer systems, a real time OS is designed to perform a task within a guaranteed time frame.
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What are the BIOS?
Basic Input Output System is the first program that runs when a computer system is switch on. The Program Counter points to the location of the BIOS upon each start up
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What is a POST?
Power on Self Test, which insures that all hardware connected is functioning correctly
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What is the purpose of The Memory Manager?
- The Memory Manager controls the allocation of RAM to each running process.
- If the memory manger fails to manage memory effectively, then the computer may slow down or crash.
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What is the Process Manager?
The Process Manager controls access to shared resources and manages the scheduling and execution of applications
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What is Multitasking?
Modern operating systems allow multiple applications to run at once. This is known as Multitasking
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What is Paging?
Paging splits the main memory into 4 kb sections known as pages. When programs run they are allowed a set number of pages to run in, these can be non-contiguous.
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What is Segmentation?
Segmentation is the splitting up of memory into logical sized divisions, known as segments, which vary in size. These are representative of the structure and logical flow of the program.
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What is Virtual Memory?
Virtual Memory uses a section of the hard drive to act as RAM when the space in main memory is insufficient to store programs being used. Sections of programs that are not currently being used are temporarily moved into virtual memory.
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What are Device Drivers?
Device Drivers are computer programs which are provided by the operating system and allow the operating system to interact with hardware. Device drivers are specific to the computer architecture, therefore different drivers must be used for different devi
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How do Drivers work?
When a piece of hardware is used, such as a keyboard, it is the device driver that communicates this request to the operating system which can then produce the relevant output.
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What are Virtual Machines?
A virtual machine is a theoretical computer in that it is a software implementation of a computer system. It provides an environment with a translator for intermediate code to run.
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What is Intermediate Code?
Code that is halfway between machine code and object code is called intermediate code. This is independent of the processor architecture so can be used across different machines and operating systems.
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What are Interrupts?
Interrupts are signals generated by software or hardware to indicate to the processor that a process needs attention.
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How are Interrupts Stored?
Interrupts are stored in order of their priority within an abstract data structure called a priority queue in the interrupt register.
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When do the Interrupts get checked?
The processor checks the contents of the interrupt register at the end of each Fetch-Decode-Execute cycle.
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What happens during the ISR?
1. Higher Priority Interrupt Exists
2. Contents of Registers moved into a Stack
3. Correct ISR loaded into RAM
4. Previous Register Contents loaded back
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What is Scheduling?
Scheduling is a core function of operating systems that ensures all sections of programs being run (or jobs) receive a fair amount of processing time. This is done by implementing various scheduling algorithms.
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What is Pre-emptive Scheduling?
Jobs are actively made to start and stop by the operating system. Examples: Multilevel Feedback Queues, Shortest Remaining Time, Round Robin.
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What is Non Pre-emptive Scheduling?
Once a job is started, it is left alone until it is completed. Examples: First Come First Served, Shortest Job First.
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What happens during Round Robin Scheduling?
1. Each Job Given a Time Slice
2. Once all Jobs have used their time slice, they are granted an equal slice of time.
3. Continues until a job has completed
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What are Multilevel Feedback Queues?
Multilevel Feedback Queues makes use of multiple queues, each of which is ordered based on a different priority.
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What is Shortest Remaining Time?
The queue storing jobs processed is ordered according to the time left for completion, with the jobs with the least time to completion being serviced first.
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What is First Come First Served Scheduling?
Jobs are processed in chronological order by which they entered the queue.
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What is Shortest Job First?
The queue storing jobs to be processed is ordered according to the time required for completion, with the longest jobs being serviced at the end.
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Other cards in this set

Card 2


What is the purpose of the OS?


The OS controls the hardware within a computer by using “Managers” and also provides a API (Application Programming Interface).

Card 3


What is the API?


Preview of the front of card 3

Card 4


What are the 5 Managers?


Preview of the front of card 4

Card 5


What are Distributed Operating Systems?


Preview of the front of card 5
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