1.2.1. Systems Software

Question 1

What is an operating system?

Answer 1

a collection of programs that work together, to provide an interface between the user and computer

Question 2

What are the functions of an operating system?

Answer 2

1. memory management
2. user interface
3. utility software
4. file management

5.interrupt service routine

6.I/O management

7.security

Question 3

What is a similarity of paging and segmentation?

Answer 3

both are used when RAM space is insufficient, which can cause disk thrashing

Question 4

What is a difference between paging and segmentation? (2 things)

Answer 4

• paging uses equal sized sections called pages
• segmentation uses variable sized, logical sections call segments

Question 5

How is virtual memory used when there is not enough RAM? (3 things)

Answer 5

1. a section of the hard drive is used to act as RAM
2. sections of programs not currently being used are temporarily moved into virtual memory through paging
3. freeing up memory for other programs in RAM

Question 6

What is an interrupt?

Answer 6

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

Question 7

What is the process of the interrupt service routine? (6 steps)

Answer 7

1. interrupt register is checked at the end of each fetch-decode-execute cycle
2. if there is an interrupt that exists with a higher priority compared to the current process, the current contents of the registers in the CPU are transferred into a stack
3. the relevent interrupt service routine is loaded into RAM
4. a flag is set to signal that the ISR has begun and is reset once the ISR has finished
5. the interrupt register is checked again, if there are interrupts of a higher priority, the process is repeated
6. if there are no interrupts with a high priority, the contents of the stack are popped and placed back into the special memory registers

Question 8

Which of these scheduling algorithm are pre-emptive or non pre-emptive?
FCFS, SRT, SJF, MLFQ, RR

Answer 8

pre-emptive - RR, SRT, MLFQ
non-preemptive - FCFS, SJF

Question 9

What is an advantage of using multilevel feedback queues for scheduling?

Answer 9

Makes use of mutiple queues to properly distrubute priority

Question 10

What is a disadvantage of using multilevel feedback queues for scheduling?

Answer 10

hard to implement

Question 11

What is the defenition of a real-time operating system?

Answer 11

real-time operating systems perform a task within a guaranteed time frame

Question 12

Where are real-time operating systems used?

Answer 12

in systems where a response within a given time frame is critical

Question 13

What are the 3 functions of the BIOS when running tests upon computer start up?

Answer 13

1. POST which ensures all hardware is correctly connected and functional
2. checks the CPU clock, memory and processor
3. tests for external memory devices

Question 14

What is the role of a device driver?

Answer 14

to enable the OS to interact with hardware devices

Question 15

What are 3 examples where a virtual machine may be used?

Answer 15

1. creating development envrionments testing programs
2. protection from malware
3. running software, compatible with different versions and types of operating systems

Question 16

What is an advantage of intermediate code?

Answer 16

Code that is halfway between machine code and object code, independent of the processor architecture

Question 17

What is an disadvantage of intermediate code?

Answer 17

considerably slower compared to running low-level code on the device it was designed for

Question 18

What are 3 examples of where real-time operating systems are used?

Answer 18

1. self driving cars
2. life support sytems
3. power systems

Question 19

What does POST stand for?

Answer 19

power on self test