1. COURSE: COMPUTER PLATFORMS

2. Topic: INTRODUCTION TO SOFTWARE AND OPERATING SYSTEMS

3. OBJECTIVES Components of a computer system
Interpret the basic functions of Operating System
Files and directory structure
Client-Server Model
Network Operating System

4. COMPONENTS OF A COMPUTER SYSTEM
The computer system is basically
divided into 4 components:
Hardware
Operating System
Application programs
Users

5. ABSTRACT OVERVIEW Users Application Programs Operating system
Computer Hardware

6. HARDWARE
This provides the Basic system
resources.

7. SYSTEM SOFTWARE
Refers to the Operating system and all utility programs that manage computer resources at a low level.
It includes compilers, loaders, linkers and debuggers.

8. APPLICATION PROGRAMS A program or group of programs
designed for end users.
Examples: Word processing, Graphics,
Spreadsheets, Databases,
Games.

9. GOALS OF AN OPERATING SYSTEM
To make the computer system convenient to use.
To use the computer hardware in an efficient manner.

10. PURPOSE OF AN OPERATING SYSTEM
The purpose of an operating system is to provide an environment in which a user may execute programs.

11. WHAT IS AN OPERATING SYSTEM?
An Operating System is an interface between user and hardware of a computer system.
The most important program that runs on a computer. Every general-purpose computer must have an operating system to run other programs. Operating systems perform basic tasks, such as recognizing input from the keyboard, sending output to the display screen, keeping track of files and directories on the disk, and controlling peripheral devices such as disk drives and printers.
For large systems, the operating system has even greater responsibilities and powers. It is like a traffic cop -- it makes sure that different programs and users running at the same time do not interfere with each other. The operating system is also responsible for security, ensuring that unauthorized users do not access the system.
Operating systems can be classified as follows:
multi-user : Allows two or more users to run programs at the same time. Some operating systems permit hundreds or even thousands of concurrent users.
multiprocessing : Supports running a program on more than one CPU.
multitasking : Allows more than one program to run concurrently.
multithreading : Allows different parts of a single program to run concurrently.
real-time real_time: Responds to input instantly. General-purpose operating systems, such as DOS and UNIX, are not real-time.
Operating systems provide a software platform on top of which other programs, called application programs, can run. The application programs must be written to run on top of a particular operating system. Your choice of operating system, therefore, determines to a great extent the applications you can run. For PCs, the most popular operating systems are DOS, OS/2, and Windows, but others are available, such as Linux.
As a user, you normally interact with the operating system through a set of commands. For example, the DOS operating system contains commands such as COPY and RENAME for copying files and changing the names of files, respectively. The commands are accepted and executed by a part of the operating system called the command processor or command line interpreter. Graphical user interfaces allow you to enter commands by pointing and clicking at objects that appear on the screen.

12. WHAT IS AN OPERATING SYSTEM?
An Operating System is a system software which may be viewed as an organized collection of software consisting of procedures for operating a computer and providing an environment for execution of programs.

13. OTHER DEFINITIONS An Operating System is a control program.
An Operating System is similar to a Government.
An Operating System can be defined as a Resource Manager.

14. OTHER DEFINITIONS
An Operating System is the layer between the H/W and the S/W
An Operating System is a virtual computer manager
Operating System is the first program run on a computer when the computer boots up

15. USER INTERFACE A set of commands or menus through
which user communicates with the
program.

16. TYPES OF INTERFACES Command driven Menu driven
Graphical user interface(GUI)
The junction between a user and a computer program. An interface is a set of commands or menus through which a user communicates with a program. A command-driven interface is one in which you enter commands. A menu-driven interface is one in which you select command choices from various menus displayed on the screen.
The user interface is one of the most important parts of any program because it determines how easily you can make the program do what you want. A powerful program with a poorly designed user interface has little value. Graphical user interfaces (GUIs) that use windows, icons, and pop-up menus have become standard on personal computers.

17. WAYS TO INTERACT WITH OPERATING SYSTEM
OPERATING SYSTEM CALLS
OPERATING SYSTEM COMMANDS
Programs rely on facilities provided by the o/s to gain access to computer system resources. There are two ways one can interact with o/s namely, system calls and system commands.

18. OPERATING SYSTEM COMMANDS
SYSTEM CALLS
System Calls provide the interface to a
running program and the O/S.
OPERATING SYSTEM COMMANDS
Users nay interact with the O/S directly
by means of O/S commands.
User program receives o/s services through the set of system calls. The following system calls will be generated by the o/s:
Prompt messages for inputting file names and reading it from terminal.
Open source and destination file
Prompt error messages.
Read the source file.
Write into the destination file.
Sysem commands can be given directly. For example to display directories in MSDOS we give the command “dir”

19. MULTIPROGRAMMING
Multiprogramming was used as a technique to enhance the throughput efficiency.
Overlapping interleaving computing of different jobs.
More than one job is “ready” at the same time.
The ability to execute more than one task at the same time, a task being a program. The terms multitasking and multiprocessing are often used interchangeably, although multiprocessing sometimes implies that more than one CPU is involved.
In multitasking, only one CPU is involved, but it switches from one program to another so quickly that it gives the appearance of executing all of the programs at the same time.
There are two basic types of multitasking: preemptive and cooperative. In preemptive multitasking, the operating system parcels out CPU time slices to each program. In cooperative multitasking, each program can control the CPU for as long as it needs it. If a program is not using the CPU, however, it can allow another program to use it temporarily. OS/2, Windows 95, Windows NT, the Amiga operating system and UNIX use preemptive multitasking, whereas Microsoft Windows 3.x and the MultiFinder (for Macintosh computers) use cooperative multitasking.

20. Different types of Multiprogramming Operating System
Multitasking operating system
Multiprocessing operating system
Multi-user operating system
Operating systems can be classified as follows:
multi-user : Allows two or more users to run programs at the same time. Some operating systems permit hundreds or even thousands of concurrent users.
multiprocessing : Supports running a program on more than one CPU.
multitasking : Allows more than one program to run concurrently.
multithreading : Allows different parts of a single program to run concurrently.
real-time real_time: Responds to input instantly. General-purpose operating systems, such as DOS and UNIX, are not real-time.

21. FUNCTIONS OF OPERATING SYSTEM
Memory management 
Process management 
Device management 
Information management 
Protection 
Error Handling

22. FUNCTIONS OF OPERATING SYSTEM
Memory management 
Process management
The o/s keeps track of
the memory, what parts are
in use and by whom. 
Device management 
Information management
Memory management is primarily concerned with allocation of main memory of united capacity to requesting processes.Two important features of memory management function are protection and sharing. 
Protection 
Error Handling

23. FUNCTIONS OF OPERATING SYSTEM
Memory management 
Process management 
Device management
The o/s keeps track of
processors and the status
of processes. It decides
who will have a chance to
use the processor. 
Information management
Process management is concerned with the management of physical processors(CPU’s) I.e., allocation of processes to a processor. A process is a program under execution. 
Protection 
Error Handling

24. FUNCTIONS OF OPERATING SYSTEM
Memory management 
Process management 
Device management 
Information management
The o/s keeps track of the devices,
channels, control units and
decides what is an efficient
way to allocate the device. 
Protection 
Error Handling

25. FUNCTIONS OF OPERATING SYSTEM
O/S keeps track of the information,
its location, use, status etc.
and decides who gets use
of the resources,
enforce protection requirements. 
Memory management 
Process management 
Device management 
Information management
File management is one of the most visible services of an operating system.File management deals with the management of data program which reside on secondary storage device. File mapping is done by file management.File management includes:
1.Mapping of logical file address to physical disk address.
2.Management of disk space and allocation and dellocation
3.Keeping track of all files in the system.
4.Support for protection and sharing of files recoveryl. 
Protection 
Error Handling

26. FUNCTIONS OF OPERATING SYSTEM
An o/s is to protect the user
from unauthorized access
of his files or data.
And also it should protect
itself from users 
Memory management 
Process management 
Device management 
Information management 
Protection 
Error Handling

27. FUNCTIONS OF OPERATING SYSTEM
An o/s must respond to
errors by taking the
appropriate actions. 
Memory management 
Process management 
Device management 
Information management 
Protection 
Error Handling

28. FILE CONCEPT File is a collection of related information.
It is named and is referred by its name.
Files are organized into directories for
easy access.
These are commonly store on secondary storage devices. File mapping is done by file management. File often appears as as sequence of bits,bytes, lines or records whose meaning is defined by programmer.

29. DIRECTORY STRUCTURE
ROOT D0 D1 D2 D3 F1
F31
F21
D21
D31
F311
D311

30. CLIENT-SERVER MODEL User process(client process) sends the
request to a server process, which
when does the work and sends back
the answer.

31. CLIENT-SERVER ARCHITECTURE
CLIENT is an application that runs on a
personal computer or on a workstation
and relies on SERVER to perform some
operations such as managing files,
disk drives, printers or network traffic.

32. NETWORK OPERATING SYSTEM
The Software that enhances a basic
Operating System by adding Networking
Features.
Examples: Novell Netware, WINDOWS NT

33. Operating system is an essential component of system software which consists of procedures for managing computer resources.
Operating system functions primarily includes Memory, Process,Device, File management.