Software. Operating systems (lecture 3)

1. Lecture 3 Topic: Software. Operating Systems

2.

Software is a generic term for
organized collections of computer
data and instructions, often broken
into two major categories:
system software that provides the
basic non-task-specific functions of
the computer,
application software which is used
by users to accomplish specific tasks.

3. Software classification

4. What is an Operating System?

a set of programs that provide
management of computer equipment,
planning efficient use of its resources and
the tasks for user tasks.
OS goals:
Control/execute user/application programs.
Make the computer system convenient to use.
Ease the solving of user problems.
Use the computer hardware in an efficient
manner.

5. The Three Elements of an OS

User Interface – The part of the OS that you
interface with.
Kernel – The core of the OS. Interacts with
the BIOS (at one end), and the UI (at the
other end).
File Management System – Organizes and
manages files.

6. Where does the OS fit in?

7. Basic functions of the operating system

Device configuration
Controls peripheral devices connected to the computer
File management
Operating
System
Transfers files between main memory and secondary
storage, manages file folders, allocates the secondary
storage space, and provides file protection and
recovery
Memory management
Allocates the use of random access memory (RAM) to
requesting processes
Interface platform
Allows the computer to run other applications

8. Common Operating Systems and Their Differences

Network Operating System
Desktop Operating System
UNIX / Linux / MS Windows2000 Server
MS Windows 9X/Me / Mac OS / DOS
Mobile Operating System
Palm OS and Pocket PC

9. Types of OS:

Operating System can also be classified as
Single User Systems
Multi User Systems

10. Single User Systems:

Provides a platform for only one user at a
time.
They are popularly associated with Desktop
operating system which run on standalone
systems where no user accounts are
required
Example: DOS

11. Multi-User Systems:

Provides regulated access for a number of users
by maintaining a database of known users
Refers to computer systems that support two or
more simultaneous users

12. Examples of Multiuser Operating Systems

Linux/UNIX
MAC OS X
Red Hat Linux
SUN UNIX
Microsoft NT, 2000
And many others, mostly on mainframes and minicomputers
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13. Advantages/Disadvantages of Multiuser Operating Systems

Advantages
Central location for the
installation and administration
of all software and data
More cost effective - less
expensive than multiple
computers (PCs, Macs)
Disadvantages
Single source for possible
problems
Loss of individual user control
of their own software, data,
and peripherals
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14. Virtual Memory

Virtual Memory (VM) = the ability of the CPU and the operating
system software to use the hard disk drive as additional RAM when
needed (safety net)
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15. Type of Operating System

Batch processing
Real time processing
Time sharing processing

16. Batch processing

Jobs, together with input data, are fed
into the system in a batch.
The jobs are run one after another.
No job can be started until previous job
is completed

17. Real time processing

immediate response is needed
For example
anti-missile defense system (в
противоракетной обороне)
airplane landing control system (система
управления посадки самолета)

18. Time sharing processing

Each user is given a time slice to interact
with the CPU (Каждый пользователь
получает время, чтобы
взаимодействовать с процессором).
The size of the time slice will depend on
the system.
Each user is served in sequence.

19. Time-sharing between process A and process B

20. Processes

Process: The activity of executing a program
(NOT THE SAME THING AS A PROGRAM!!!)
Program – static set of directions (instructions)
Process – dynamic entity whose properties change
as time progresses. It is an instance in execution
of a program.
Process State: Current status of the activity
Program counter
General purpose registers
Related portion of main memory

21. Different Types of Operating System

22. Memory Manager

Has the task of coordinating the use of main
memory – allocates/deallocates space in main
memory
When the total required memory space
exceeds the physical available space.
May create the illusion that the machine has more
memory than it actually does (virtual memory)
by playing a “shell game” in which blocks of data
(pages) are shifted back and forth between main
memory and mass storage

23. Operating System Structure

Multiprogramming needed for efficiency
Single user cannot keep CPU and I/O devices busy at all
times
Multiprogramming organizes jobs (code and data) so CPU
always has one to execute
A subset of total jobs in system is kept in memory
One job selected and run via job scheduling
When it has to wait (for I/O for example), OS switches to
another job
Unlike sitting idle in a non-multiprogrammed system
The idea is common in other life situations (e.g., lawyers)
as long as at least one job needs to execute, the CPU is never idle…

24. Utility is

a program that performs a very specific
task, usually related to managing
system resources.
Operating systems contain a number of
utilities for managing disk drives,
printers, and other devices.

25. Questions:

1.Classification of software
2. Operating system is …
3. Elements of operating system
4. Classifications of operating system
5. Virtual memory is …
6. Utility is…
7. Examples of utility