The document provides an overview of operating systems, detailing their role as intermediaries between software and hardware, types of software (system and application), and key characteristics of various operating systems such as single-tasking and multi-tasking designs. It discusses different multitasking approaches including cooperative and preemptive multitasking, as well as concepts like multi-threading and symmetric multiprocessing. Additionally, it covers user interfaces, the historical development of notable operating systems including Unix, MS-DOS, Mac OS, and Windows, emphasizing their evolution and features.

1. OPERATING SYSTEM

2. OS – The Operating System
 Agent between Software and H/W
 User intervention is not required
 Two types of Computer S/W;
 System Software
 Application S/W
 OS make sure resources are available for all
the processes.
 OS supports a particular type of processor
 What is your OS ?

3. OS and CPU
 Single tasking OS
 Run only one application at a time.
 MS-DOS
 Multi Tasking OS
 User can work on multiple program simultaneously at single time.
 CPU don’t run programs together; it switches as needed
 Active Program: Foreground Prog. Inactive Prog: Background Prog
 Multi-tasking is different than time-sharing
 Cooperative Multi-tasking
 Different program controls CPU at different time
 Foreground program gains CPU hold
 If the Foreground Prog is crashed then OS will hang
 Mac OS and Windows earlier version used this way
 Preemptive Multi Tasking
 Enable OS to regain hold of CPU even if one program is crashed
 Each process is given a slice of time
 When time expires the OS preempts the process and slice is given to another process
 Linux, Windows 95, Windows 98, Windows NT
 Multi Threading
 Extended concept og Multi-Tasking
 Allows idividual programs to caerry out multi-ple task simultaneously
 Each task is called thread
 Computer can execute more than one task in a single program
 Ex web page takes long time to load, you click to close it, then a seerate thread cclose the wiindow
 Symmetric Multi Processing
 User of two or more processor ata a time
 Linux, windows NT and Mac OS 8

4. User Interface
 Command Line User Interface
 Character based user interface
 Promt is shown to user to make a command
 It have predefined set of rules called syntax
 Mostly used in system administrative task
 Menu driven User Interface
 Interface provides range of options to choose
command and then enter to prompt
 Graphical User Interface
 Desktop, Pointer, Pointing Device, icons and
windows

5. Types of OS
 UNIX
 Developed in early 70’s at Bell Labs
 UNIX was written in C language
 Main motive was to enable programmers to access
system and share resources simultaneously.
 It lacks in incompatibility with different versions,
cryptic commands and lack of user-friendliness
 MS DOS
 Disk Operating System
 MS developed DOS for IBM compatible computers
 Character based and single tasking OS

6. Types of OS ( contd.)
 Mac OS
 Macinstosh OS was developed by Apple Inc.
 This OS featured GUI for the first time
 Released in 1984
 First time easiest OS for first time PC users
Windows 3.X
Released in 1990
Enabled users to take advantage of Intel’s 32-bit
processor
Intel newly offered protected mode – acess virtually
unlimitaed amount of memory
Windows 3.1, 3.11 – collectively called Windows 3.X

7.  Windows 3.0
 SDK – the new feature
 Windows 3.1
 Mouse was introduced as input device
 Windows 3.11
 Peer-to-peer workgroups
 Workgroups were introduced

8.  Windows 95 & 98
 Windows Me
 September 2001