Systems Software

Question 1

What is the role of an Operating System?

Answer 1

The operating system acts as an interface between the hardware and software.

Question 2

What is the kernel?

Answer 2

The kernel is part of the OS that is responsible for the most low-level hardware operations (e.g: managing CPU, memory devices, etc)

Question 3

What are the 4 main functions of an OS?

Answer 3

• User Interface
• Memory Management
• Peripheral Management
• Multitasking

Question 4

Why is memory management necessary?

Answer 4

• Allows programs larger than memory to run
• Protects programs from overwriting each other

Question 4

What are the two main methods for an OS to manage memory?

Answer 4

Memory Paging and Memory Segmentation

Question 5

What is memory paging?

Answer 5

Data is split up physically into equally-sized pages and placed in non-contiguous memory spots.

Question 6

How does the OS know where to locate specific memory pages?

Answer 6

Given an address, the Operating System(OS)/Memory Management Unit(MMU) translates it to a primary memory location.

Question 7

What is memory segmentation?

Answer 7

Memory is split up logically into modules/functions, and are placed in non-contiguous memory locations.

Question 8

What is virtual memory?

Answer 8

Using secondary storage as a temporary store when RAM is full. Programs/data not in use are moved to and from virtual memory via paging.

Question 9

What is an issue with paging/segmentation/virtual memory?

Answer 9

Disk thrashing is when pages are swapped between virtual memory and RAM too much, and less time is spent actually running programs.

Question 10

What is a Distributed OS?

Answer 10

A distributed OS coordinates multiple computers to act as one or to contribute resources to a task.

Question 11

What is an Embedded OS?

Answer 11

An embedded OS is designed for specific hardware/functions, typically can’t be changed, and uses the device hardware/power efficiently.

Question 12

What are the five main types of OS?

Answer 12

• Distributed OS
• Embedded OS
• Multi-Tasking OS
• Multi-User OS
• Real-Time OS

Question 13

What is a Multi-User OS?

Answer 13

Allows multiple users to use the computer at the same time. Typically found in servers, but must use a scheduling algorithm so users get enough CPU time.

Question 14

What is a Multi-Tasking OS?

Answer 14

Makes it seem as though processes are done in parallel by giving different processes different amounts of CPU time and quickly going through them. Used in most PCs.

Question 15

What is an interrupt?

Answer 15

A signal is generated by software or hardware to indicate to the processor that a process needs attention.

Question 15

What is a Real-Time OS?

Answer 15

A real-time OS is designed to process certain data within a guaranteed time frame, and is found in time-sensitive systems like self-driving cars.

They typically have fail-safe features such as backup hardware.

Question 15

Why does an OS need scheduling?

Answer 15

The OS needs scheduling so that processes are given a fair amount of CPU time, and appear to be operating in parallel.

Question 16

What is the Interrupt Service Routine?

Answer 16

When the CPU receives an interrupt, the ISR will evaluate the interrupt’s importance, storing it in a queue or servicing it if need be.

Question 17

What are the 5 main scheduling algorithms?

Answer 17

• Round Robin
• First Come, First Serve
• Shortest Job First
• Shortest Remaining Time First
• Multi-level Feedback Queue

Question 18

What is the Round Robin algorithm?

Answer 18

Each job is given an equal amount of CPU time, and if not finished, is sent to the back of the queue.

Question 19

What is the First Come, First Serve algorithm?

Answer 19

The first task is the queue is completely processed, then the second, etc.

Question 20

What is the Shortest Job First algorithm?

Answer 20

The shortest job in the queue is given priority. The current job is completed fully even if a shorter job now exists.

Question 21

What is the Shortest Remaining Time algorithm?

Answer 21

The job with the least amount of time left before it MUST be finished is given priority. Jobs that don’t need to be done immediately are given low priority.

Question 21

What is the Multi-level Feedback Queue?

Answer 21

The OS makes use of multiple queues, each with different functions/priorities (e.g.: peripheral queue) that the CPU can schedule separately to ensure CPU time is used efficiently.

Question 22

What is the BIOS?

Answer 22

The Basic Input Output System is the program first run upon powering on a computer before the OS is loaded.

Question 22

What problem may arise from certain scheduling algorithms?

Answer 22

Some algorithms can lead to process starvation, where certain jobs are never processed.

Question 23

What is the role of the BIOS?

Answer 23

The BIOS has a Power-On Self-Test (POST) that ensures all hardware is connected and functioning, and checks if the CPU and external memory are functional.

Question 24

What is a device driver, and why are they needed?

Answer 24

A driver is a piece of software for a piece of hardware that allows it to communicate with the operating system.

Question 25

What is a virtual machine?

Answer 25

A virtual machine is software that emulates a computer/operating system within a computer.

Question 26

What is intermediate code and why is it good?

Answer 26

Intermediate code is portable, partially translated code that can run across devices and operating systems and is used in virtual machines. It is slightly slower than running compiled code tho.

Question 27

What are the common uses of virtual machines? [4]

Answer 27

• Can be used by programmers to test code across devices/OSs
• Multiple VMs can be run off of one physical computer, giving the illusion of having multiple PCs
• VMs can be used to emulate certain devices like consoles
• Malware will affect the VM and not the host PC.

Question 28

What is a buffer and why does the OS need it?

Answer 28

The buffer is a small partition of secondary storage that the OS uses to manage slow peripheral operations more efficiently.

Question 29

What is spooling?

Answer 29

Spooling is where peripheral requests are added to a queue/buffer, with each request being seen in turn, so that the CPU is free to deal with other requests.