Operating Systems

Question 1

What is an Operating System?

Answer 1

A software that acts as an intermaiedary between users and hardware

Question 2

Functions of operating systems

Answer 2

-Oversee operation of computer
-Store and retrieve files
-Schedule programs for execution
-Coordinate the execution of programs

Question 3

OS as …..
OS as …..

Answer 3

OS as extended machine (resource allocator)
OS as a resource manager (control program)

Question 4

Components of Computer System

Answer 4

Computer Hardware>Operating Systems>Sytem and Application Programs>Users

Question 5

Evolution of shared computing

Answer 5

Batch processing : Add to queue and wait
Interactive processing : Requires real-time processing
Time-sharing/Multitasking : Implemented by multiprogramming
Multiprocessor machines :

Question 6

Types of Software

Answer 6

Application Software : Specific tasks for users
System Software : Provides infrastructure for application software and consists of “operating system and utility software”

Question 7

Software Classification

Answer 7

Software - Application
\
System - Utility
\
Operating System - User interface
\
Kernel

Question 8

Operation System Components

Answer 8

User interface : Communicates with users
+Text based (Shell)
+Graphical user interface (GUI)
Kernel : Performs basic required functions
+File manager
+Device drivers
+Memory manager
+Schedular and dispatcher

Question 9

File Manager

Answer 9

Directory (or Folder) : A user-created bundle of files and other directories (subdirectories)
Directory path : A sequence of directories within directories

Question 10

Memory Manager

Answer 10

+Allocates space in main memory
+Virtual memory by playing a “shell game” in which blocks of data (pages) are shifted back and forh between main memory and mass storage

Question 11

Getting it started

Answer 11

=Bootstrapping
Boot loader : Program in ROM (example of firmware)
-Run by the CPU when power is turned on
-Transfers operating system from mass storage to main memory
-Executes jump to operating system

Question 12

Processes

Answer 12

Process : The activity of executing a program
Process state : Current status of the activity
-Program counter
-General purpose registers
-Related portion of main memory

Question 13

Process administration

Answer 13

Schedular : Adds new processes to the process table and removes completed ones
Dispatcher : Controls the allocaation of time slices to the processes in the process table *the end of a time slice is signaled by an interrupt

Question 14

Handling Competition for Resources

Answer 14

Semaphore : A “control flag”
Critical Region : A group of instructions that should be executed by only one process at a time
Mutual exclusion : Requirement for proper implementation (yürütme) of a critical region

Question 15

Deadlock

Answer 15

Processes block each other from continuing
Conditions required for deadlock
1-Competition for non-sharable resources
2-Resources requested on a partial basis
3-An allocated resource cannot be forcibly retieved

Question 16

Dining Philosophers Problem

Answer 16

The sleeping barber problem

Question 17

Security

Answer 17

+Attacks from outside
-Problems :
>Insecure passwords
>Sniffing software
-Counter measures
>Auditing software
+Attacks from within
-Problem : unrurly processes
-Counter measures : Control process activities via priviliged modes and priviliged instructions