Chapter 3: Part 1 Flashcards
What is an operating system?
A collection of programs that work together to provide an interface between the user and computer
Give 3 functions of an operating system.
Three from:
- Memory management
- Resource management
- I/Output management
- Interrupt management
- Security
- User interface
- Utility software
What are the similarities and differences between
paging and segmentation?
Both: Are used when RAM space is insufficient, can cause disk thrashing
Paging: Uses equal-sized sections called pages
Segmentation: Uses variable-sized, logical sections called segments
Describe how virtual memory is used when there is
not enough RAM.
A section of the hard drive is used to act as RAM
Sections of programs not currently being used are temporarily moved into virtual memory through paging.
This frees up memory for other programs in RAM.
What is an interrupt?
A way for an external device to request the use of processor time. If an interrupt is made the processor halts the shcedule and performs the appropriate interrrupt servie routine.
Explain the stages of the Interrupt Service Routine.
-Completes the FDE cycle it is currently working on
-Saves the contents of the Program Counter and Registers onto the Stack
-Identifies The Source of the Interrupt
-Disables all interrupts of a lower priority
-Loads and runs the appropriate ISR
-Restore the Registers from the Stack
-Re-enable all Interrupts
-Resume the execution of normal service
Are the scheduling algorithms pre-emptive or non
pre-emptive?
Pre-emptive: RR, SRT, MLFQ
Non-pre-emptive: FCFS, SJF
Give one advantage and disadvantage of using
Multilevel Feedback Queues for scheduling.
Advantage: Services most urgent
interrupts first
Disadvantage: Hard to implement
Define a real-time operating system and when it may
be used.
Real-time operating systems perform a task
within a guaranteed time frame. They are used in
systems were a response within a given time
frame is critical eg. life support systems,
self-driving cars, power systems.
Describe three functions of the BIOS.
Running tests upon the computer’s start-up:
● POST (Power-on self test) which ensures that all
hardware is correctly connected and functional
● Checking the CPU clock, memory and processor
● Testing for external memory devices
What is the role of a device driver?
Enable the operating system to interact
with hardware devices.
Describe an instance in which a Virtual Machine may
be used.
● Testing programs
● Protection from malware
● Running software compatible with different versions and types of operating systems
Give one advantage and one disadvantage of
bytecode.
Advantage: Platform independent,
portable
Disadvantage: Slower execution
Describe the similarities and differences between a Page Table, Segment, Table and a Directory.
ALL 3 STORE THE PHYSICAL ADDRESSES OF DATA IN MEMORY
PAGE AND SEGMENT TABLES MAP THE LOGICAL ADDRESSES OF THE CODE TO THE PHYSICAL ADDRESSES IN PRIMARY MEMORY THAT THE PAGES OR SEGMENTS HAVE BEEN LOADED INTO
A DIRECTORY IS USED BY THE FILE MANAGER TO KEEP TRACK OF PROGRAM AND DATA IN BACKING STORAGE
