Mid-term 1

Question 1

Bootstrap

Answer 1

Loads operating system kernel and stored in ROM. Initializes all aspects of system

Question 2

Caching

Answer 2

Copying information into faster storage system; main memory can be viewed as a cache for secondary storage

Question 3

Advantages of multiprocessors

Answer 3

1. Increased throughput
2. Economy of scale
3. Increased reliability

Question 4

Dual-mode

Answer 4

User mode, Kernel mode - allows OS to protect itself. Allows ability to distinguish between kernel code and user code. Some instructions are ‘privelaged’: only run in kernel mode.

Question 5

API

Answer 5

Application Programming Interface - provides interface for application programmers.

1. Program portability (same code runs on any machine with same API)
2. Less detailed, more abstracted

Question 6

System Call

Answer 6

Provides an interface to the services made available my an operating system

Question 7

Types of system calls

Answer 7

1. Process control
2. File manipulation
3. Device manipulation
4. Info maintenance
5. Communications
6. Protection

Question 8

Command Interpreters

Answer 8

CLI’s (Command Line Interface). Systems with multiple interpreters call them shells. Main function is to get and execute the next user-specified command

Question 9

OS Structures - Simple

Answer 9

Only one or two levels of code - provides most functionality in least space, but is vulnerable

Question 10

OS Structures - Layered

Answer 10

Lower levels independent of upper levels - More secure, but more overhead since layers can only communicate with one directly below it

Question 11

OS Structures - Microkernels

Answer 11

OS built from many user processes - moves as many processes as possible to the ‘user’ space, small kernel. More reliable and secure, suffers performance overhead from user to kernel

Question 12

OS Structures - Modules

Answer 12

Core kernel with dynamically loadable modules - Uses OO approach. Similar to layers, but more flexible

Question 13

Virtual Machine

Answer 13

Software implementation of a computer that executes programs like a physical machine. System Machines exist independently on hardware, Process Machines run as an app inside an OS

Question 14

Process Parts

Answer 14

1. Program Code
2. Program Counter
3. Stack
4. Data Section
5. Heap

Question 15

Process States

Answer 15

Question 16

PCB

Answer 16

Info associated with each process.

State, counter, CPU registers, scheduling, memory info, accounting info, I/O status

Question 17

Process Scheduling

Answer 17

Scheduler selects among available processes for next execution on CPU.

Long-term - selects processes to be brought into ready queue. Short-term - Selects which program to execute next on CPU

Question 18

Scheduling Queues

Answer 18

1. Job Queue - Set of all processes on system
2. Ready Queue - set of all processes residing in main memory, ready and waiting to execute
3. Device Queues - set of processes waiting for an I/O device

Question 19

Context Switch

Answer 19

When CPU switches to another process, the system must save the state of the old process and load the saved state for the new process

Question 20

Process Creation

Answer 20

Parent process create children processes, which, in turn create other processes, forming a tree of processes. Managed via process id (pid)

Question 21

Process Termination

Answer 21

Process executes last statement and asks the operating system to delete it (exit).

Question 22

Interprocess Communication (IPC)

Answer 22

1. Independent process cannot affect or be affected by the execution of another process
2. Cooperating process can affect or be affected by the execution of another process

Question 23

Two types of IPC

Answer 23

1. Shared Memory - Less overhead
2. Message Passing - Safer

Question 24

Buffering (Producer-Consumer problem)

Answer 24

1. Zero capacity – 0 messages (no buffering) Sender must wait for receiver (rendezvous)
2. Bounded capacity – finite length of n messages. Sender must wait if link full
3. Unbounded capacity – infinite length. Sender never waits

Question 25

Socket

Answer 25

An endpoint for communication, a concatenation of the IP address and port number. Ex. 192.168.1.12:1352

Question 26

Heavywight/Lightweight Process

Answer 26

Heavyweight - Process with single thread of control

Lightweight - A single thread