Operating Systems

Question 1

What is an operating system?

Answer 1

An operating system is software that manages resources

Question 2

What are the 2 main responsibilites of an OS?

Answer 2

1. To manage the resources of a system
2. To provide an execution environment for programs

Question 3

What are the 3 main components of an OS’s structure?

Answer 3

1. UI (GUI, CLI)
2. System Call Module
3. Kernel (resource management, program execution, file system, etc.)

Question 4

What is a kernel?

Answer 4

A kernel is the core component of an operating system. A kernel is composed of services such as resource management, program execution, file system, protection and security, etc. The kernel is what communicates with the hardware of a system

Question 5

What are the 4 main hardware devices of a system?

Answer 5

1. CPU
2. Memory
3. Storage
4. I/O devices

Question 6

What is the purpose of a CPU?

Answer 6

The purpose of a CPU is to execute the instructions of a program that has been loaded into memory

Question 7

What is the difference between a single-core and multicore CPU?

Answer 7

A single-core CPU can only execute 1 process/thread at a time. A multicore CPU with N cores can execute N processes/threads at a time. Multicore CPUs make parallel execution possible

Question 8

How does CPU cache make a system more efficient?

Answer 8

CPU cache makes a system more efficient by storing future instructions so that the CPU does not have to retrieve it from memory

Question 9

What data structure is normally used to represent memory?

Answer 9

An array of bytes where each byte is indexed to a memory address

Question 10

What are the 3 attributes that you should keep in mind when comparing memory and storage?

Answer 10

1. Speed
2. Size
3. Volatility

Question 11

What is a process?

Answer 11

A process is a program (executable) that has been loaded into memory for execution

Question 12

Give an illustration of the structure of a single-threaded process

Answer 12

• Heap (allocated memory)
• Stack (function call memory)
• Global data (initialized/uninitialized variables)
• Code (executable code)
• Thread (basic unit of executaion by the CPU)

Question 13

Give an illustration of the structure of a multithreaded process

Answer 13

• Heap (allocated memory) shared
• Stack (function call memory) not shared
• Global data (initialized/uninitialized variables) shared
• Code (executable code) shared
• Threads (basic unit of executaion by the CPU)

Question 14

When a process is created what data structure does the OS create to represent that process and where is it stored?

Answer 14

A process control block which contains the process ID, process state, and other information needed by the OS. This data structure is stored in kernel space

Question 15

Can 2 processes communicate with one another?

Answer 15

Yes, but this is not the default setting. If 2 processes agree to communicate with one another, they can do so by either shared memory or message passing

Question 16

What is a thread?

Answer 16

A thread is the basic unit of execution by the CPU

Question 17

When a thread is created, what data structure does the OS create to represent that thread and where is it stored?

Answer 17

A thread control block which contains the thread ID, thread state, and other information needed by the OS. This data structure is stored in kernel space

Question 18

Can threads communicate with one another?

Answer 18

Yes. Since threads share the same code, global data, and heap of the current process, they can communicate faster than a process communicates with another process

Question 19

What is a thread pool?

Answer 19

A thread pool is a set of threads created by a program at start up. The logic is the same for connection pools, it is more efficient to have a pool of threads ready for use than to create and terminate a thread whenever it is needed

Question 20

What are the 2 main reasons why applications are operating-system specific?

Question 21

How can an application be made available to run on multiple operating systems?