Systems Software Flashcards
1
Q
What is the interupt process?
A
- Interupt request
- Importance of interupt is decided
- Coressponnding Interupt Service Routine (ISR) is found
- ISR execution
- Interupt exit
2
Q
What happens if the interupt is more important than the current task?
A
- FDE cannot be stopped halfway so current FDE cycle is completed
- Contents of registers is temporarily saved to memory
- Processor hands control to coressponding ISR which completes response
- Contents of registers is restored
3
Q
What is interupt prioritisation and nesting?
A
- Interupt prioristisation is the processors ability to switch to higher priority interupts
- Nesting is the processors ability to deal with interupts within interups
- Proper management of nesting allows the system to remain stable
4
Q
What is scheduling?
A
- Deciding which tasks to process, for how long and in which order is achieved through scheduling
- A CPU is responsible for processing tasks as fast as possible
- Different algorithms are used to prioritise different tasks in different ways
5
Q
What is round robin scheduling?
A
- Equally distributes processing time amongst all tasks
- All tasks put in a queue
- If the task hasn’t been completed by the end of its time quantam (allocated time) it is moved to the back of the queue
6
Q
What is multi-level feedback queue scheduling?
A
- Shorter and more critical tasks are processed first
- All tasks join the highest priority but trickle down to lower priorities if they exceed the time quantam
7
Q
Why is memory management necessary?
A
- When a user opens an application, its data is loaded from storage into active memory so that it can run smoothly
- Primary memory is a limited resource so must be carefuly managed to allow efficient multi-tasking
8
Q
What 3 techniques are used in memory management?
A
- Paging
- Segmentation
- Virtual memory
9
Q
What is paging and how does it work?
A
- Method of chunking memory into equal-size blocks
- These chunks are known as pages
- Pages will be taken away from applications not in use and allocated to active applications
- Paging can lead to internal fragmenation
- Internal fragmentation will lead to unused memory
10
Q
What is memory segmentation and how does it work?
A
- Chunking memory into blocks that correspond to different types of data needed by an application
- Segments are not all the same size and are sized depending on the allocated data
- Segmentation can lead to external fragmentation
- This is because once an application finishes, data is moved out and the space left will be of an uneven size
11
Q
What is virutal memory and how does it work?
A
- If a computer is running low on memory, it can use secondary storage as an “extension” to its primary memory
- Vram creates an illusion of a larger memory and enables applciations to continue multi-tasking
- Accessing data in vram is slower than primary memory
12
Q
What is a distributed OS?
A
- Tasks run on multiple different machines appearing as one unit
- Used for efficient task distribution
13
Q
What is an embedded OS?
A
- The system running inside a device that is not primarily a computer system
14
Q
What is the BIOS and boot sequence?
A
- The BIOS is the first system to run and tells the computer how to boot
- It completes the POST tests
- If no errors are encountered during the POST tests, the bootstrap sequence is run
15
Q
What is a device driver?
A
- A piece of software that enable communication between the operating system and specific hardware devices
- Allows the OS to control and interact with hardware devices
16
Q
What is a virtual machine?
A
- Virtual machines are entire operating systems running inside another operating system
- VM management software includes a hypervisor that monitors all activity happening inside the VM
17
Q
When are virtual machines used?
A
- Cross platform compatability: not all software is compatible to run on all operating system. You can use a virtual machine to emulate a different operating system
- Software testing: isolate test environments, leaves the host computer unaffected. Can test multiple operating systems on one computer for greater compatability
18
Q
Consequences of using virtual machines
A
- VMs share the same hardware as the host computer; over-use of VMs can exhaust the host computer
19
Q
Different types of operating systems
A
- Embedded OS: designed for a specific task, running within a device that is not specifically a computer system
- Distributed OS: tasks are run on multiple machines appearing as a single unit
- Real time OS: designed for immediate data processing and responses
- Multi-user OS: supports multiple users accessing computer resources concurrently
