Week 11 - Operating Systems #1

Question 1

1. ) Define Application Software.
2. ) Define System Software.
3. ) What does System software provide?

Answer 1

1. Software written to address the needs of the user.
2. Software written to manage the hardware of the computer system. For example, The Operating System and BIOS.
3. An Interface Between the User and System.

Question 2

1. What is the function of The Boot Program?
2. The BIOS is managed by the CPU for what purpose?

3 Drivers Are Used By The OS, But What For?

Answer 2

1. ) To load The OS into memory (RAM)
2. ) The BIOS manages the data flow between the peripherals and primary memory (E.g. The HDD, The Mouse, The Keyboard ETC.)

Question 3

What are the three main functions of the operating system (Remember! MII)

Answer 3

• Manage the Hardware and system resources (CPU, I/O devices)
• Provides and interface for the user to interact with the computer.
• Allows the application to interact with system resources.

Question 4

1. ) A modern OS can support which feature?

2. ) The Operating System must perform which action to ensure each process has sufficient time to run on the CPU?

Answer 4

1. ) Multi-tasking

2. ) Scheduling.

Question 5

1. ) Define a Physical Address

2. ) Define a Logical Address.

Answer 5

1. ) A Physical Address is the ACTUAL location in memory.

2. ) A Logical Address is the location of the memory RELATIVE to the start of the program.

Question 6

What is The Name For Converting A Logical Address To A Physical Address?

Answer 6

Address Binding

Question 7

1. ) How does The Single Contiguous Memory Management Technique Function? (What can be loaded into memory?)
2. ) How is the Physical Address Of A Section Of Code In The Program Calculated?
3. ) What is The Advantage Of Single Contiguous Memory? (1 Answer)
4. ) What Are The Two Main Disadvantages Of Single Contiguous Memory?

Answer 7

1. ) Single Contiguous Memory Stores Only Has Operating System and A Single Application In Memory At Any One Time.
2. ) The Logical Address of The Code Is Added To The Physical Address Of The Starting Point Of The Program.
3. ) Single Contiguous Memory is Simple To Implement And Manage.
4. )
   - Single Contiguous Memory Can Only Run One Program At A Time.
   - Single Contiguous Memory Is Wasteful In Terms Of Memory And CPU resources (all of it gets dedicated to a single program regardless of its size).

Question 8

1. ) How Many Programs Can Run At A Time In Partitioned Memory?
2. ) Define A Fixed Partitioning.
3. ) Define a Dynamic Partitioning.
4. ) The Operating System Maintains Two Registers Containing Two Fields For Each Partition. What are These Fields, And What Do They Represent?

Answer 8

1. ) Multiple Programs (as long as there’s space)
2. ) A Fixed Partition Is Where A Fixed Number of Partitions In Which Programs Can Be Loaded. Any Space Left Over By A Program In A Fixed Partition Cannot Be Used To Create A New Partition.
3. ) A Dynamic Partition Is Where Partitions Of Varying Size Are Created As And When Needed. Any Space Left Over By A Program In A Dynamic Partitions Can Be Used To Create Another Partition.

4.)
Base - Physical Address Of The Beginning Of The Partition.

Boundary - Physical Address Of The Length Of The Partition.

Question 9

Portioned Memory Management Uses Three Management Algorithms To Assign Memory - What are they, and how do they work?

Answer 9

Best Fit - Programs Are Stored In The Smallest Available Partition That Is Large Enough To Hold It.

Worst Fit - Programs Are Stored In The Largest Partition Available That Is Large Enough To Store The Program.

First Fit - Programs Are Stored In The First Partition That Is Large Enough To Hold The Program.

Question 10

Explain Which Memory Allocation Method Works Best For Both Dynamic And Fixed Partitioning And Why.

Answer 10

Dynamic Partitioning - Worst Fit, as more portions are created using the Space Left Over Which means more Programs can be allocated to memory.

Fixed Partitioning- Best Fit, Any unused space Cannot be reallocated as another Partition. As such, to minimise wasted memory, the smallest program is fitted into the smallest slot.

Question 11

1. ) What is the main advantage of using partitioned memory?

2. ) What are the Two Main Disadvantages To Using Partitioned Memory?

Answer 11

1.) Makes Efficient Use Of Memory By Allowing More Than One Program To Run At Once.

2. )
   - A Program That Is Large Enough To Fit Into The Memory Might In Fact Be Too Large To Fit Into An Individual Partition.

• Fixed Partitions Are Easier To Manage Than Dynamic Partitions, But Are Very Restrictive.

Question 12

What Are The Steps For Calculating The Physical Location Of A Program Using It’s Logical Address And It’s Page Number?

Answer 12

1. )
   - Divide The Logical Address By The Size Of Each Page.
   - Calculate Any Remainder To Calculate The Offset.
   - Use The PMT Table To See Which Frame Holds The Page Number You Have Calculated.
   - Multiply The Frame Size By The Frame Number That Holds The Page And Add The Offset.

Question 13

1. ) What Is Page Swapping
2. ) What Is Dynamic Page Swapping?
3. ) What Is Page Thrashing?

Answer 13

1. ) Page Swapping Is Moving A Stored Page From The Hard Drive To RAM (or Vice Versa)
2. ) Moving A Stored Page From The Hard Drive To RAM ONLY WHEN NEEDED.
3. ) Page Thrashing Is Where Multiple Programs Are Ran With Insufficient Memory. Pages Are Rapidly Swapped Backwards And Forwards Resulting In Lower Performance.