SLR4 Flashcards
What does the operating system allow the user to do
Talk to the hardware
What does application software do
Talk to a specific application. E.g. Word, PowerPoint.
What is a utility Program
A program designed to protect your computer from malware
What is multitasking
When a computer is running multiple programs at the same time
How does a computer handle multitasking
A processor allocates a small amount of time to each program and as it happens so quickly it appears instant
Where in a computer is data stored
In files
How does the operating system know which type of application a file is
There is an extension at the end of the file name declaring what it is
Name 3 benefits of having user management
- Having multiple users on one machine
- Having a roaming machine
- Each user has a different access ability
What are the two main ways of having memory management
Paging & Segmentation
What are the 4 main traits of paging
- All pages are a fixed-size
- Pages are physical divisions
- Could separate instructions making the code inefficient
- It is better to keep the instructions together
What are the 3 main traits of segmentation
- Segments are different sizes
- Segments are logical divisions
- Can lead to small amounts of memory unallocated
What is it called when a device requires the processor’s attention
An interrupt
What will the processor do if an interrupt presents a problem
The processor will stop executing its current instruction and focus on the interrupt
How does a processor handle an interrupt
The processor will activate the interrupt service routine
What is the interrupt service routine
A program with a set of instructions that need to be fetched, decoded, and executed to continue
What happens to the current process when an interrupt is received
The current process gets moved into the stack which stores the contents of the registers
Why do we have interrupts
Other devices may require the CPUs attention and their priority is greater than the current instruction
Give the 5 types of interrupt and an example of each
- Hardware (Power)
- Timer (screen record)
- Input / output (USB)
- User (mouse)
- Software (illegal instruction)
What happens when the interrupt is complete
The original instruction is popped back off the stack into the registers to be executed
What does a scheduler manage
Which process to execute next and how much time to spend on it
How is time messured in a computer
In ticks
What does running state mean
Running state is when a process is running
How does a process get to the CPU
A process will enter the queue and once it reaches the front of the queue it will enter the CPU
What happens if the process is blocked
This means that the user is required to input something
What happens when a process in the CPU takes more time than the allocated number of ticks
The process gets suspended and rejoins the back of the queue until it re-enters the CPU
What happens when a process is finished
It leaves the CPU
What does FCSC stand for
First Come First Serve
In what order does FCSC execute a process in
The first process to arrive in the queue gets executed before everything else
What does not get used in FCSC
- Blocking
- Priority
- Time suspending
What does SJF stand for
Shortest Job First
In what order does SJF execute processes in
When a job joins the queue its place will be in the order of whichever job is the shortest meaning the shortest job will always get executed first
How is the length of the job decided
The number of ticks it takes to complete
What does RR stand for
Round Robin
What other form of scheduling is RR similar too
FCSC
In what way does RR differ from FCSC
Includes a quantum time slice
What is a Quantum time slice
Each process has a set number of ticks it can be executed for before being put back in the queue again and again until it is completed
What does STR stand for
Shortest Time Remaining
Which other form of scheduling is STR similar too
SJF
How does SJR differ from SJF
If a new process joins the queue that has less ticks remaining then the process in the CPU will be kicked into quantum
What happens when a process is blocked
- It is removed from the CPU
- Until the user has confirmed it can continue
- Other processes are carried out in this time
What does MLFQ stand for
Multi-Level Feedback Queue
What is a MLFQ
Where there are multiple cores and therefore multiple levels in the queue
How can different queues spread the load of the processes
Some queues can just manage small tick time processes and other just manage large tick time processes
Can processes move between queues and cores
Yes
What are the 5 different operating systems
- Multi-tasking operating system
- Multi-user operating system
- Distributed operating system
- Embedded operating system
- Real-time operating system
What is the main feature of a multitasking OS
It is able to run multiple programs at the same time
Can a multi-tasking OS multi-task
No it just does things incredibly quickly
What are the 3 main features of a multi-user OS
- Can have multiple accounts across multiple computers
- Can login anywhere
- All ran off one server
What are the 2 main features of a distributed OS
- Combines the processing power of multiple computers
- Appears as one system
What are the 3 main features of an embedded OS
- Often designed for very specific tasks and often quite slow
- Small memory
- Low power
Where are embedded OSs found
TVs, Traffic Lights, Car engine management system
What are the 2 main features of a real-time OS
- The OS responds in real-time
- Designed around the safety of the user
What does BIOS stand for
Basic Input Output System
What is the BIOS responsible for
Loading the OS when the computer is switched on
Where is the BIOS stored
ROM as you don’t need to change it
What is a device driver
Software that tells the OS how to communicate with a device
What is a virtual machine
a program that does a physical machine job
What does an emulator do
Tricks a program into thinking it running on its native hardware whilst on an entirely different machine
What are the positives and negatives of emulators
- Brings life back to old games
- Saves money as it allows the user to test a program on another device without actually having the machine
- Does not pay the creator
- It is illegal
How can you save money with virtual machines
You can spin servers up and down based of off the demand required. Meaning if one server fails the others can pick up the load.
What is Java code
An intermediate code
How is an intermediate code designed to work
To run on many different platforms
How does Java compile its code
Into halfway code known as bytecode
Name a benefit of Java intermediate code
It is highly portable
