1. Chapter-1
Computer is an advanced electronic device that takes raw data as an input from the user and processes it under the control of a set of instructions (called program), produces a result (output), and saves it for future use. This tutorial explains the foundational concepts of computer hardware, software, operating systems, peripherals, etc. along with how to get the most value and impact from computer technology.
A computer is a programmable machine designed to perform arithmetic and logical operations automatically and sequentially on the input given by the user and gives the desired output after processing. Computer components are divided into two major categories namely hardware and software. Hardware is the machine itself and its connected devices such as monitor, keyboard, mouse etc. Software are the set of programs that make use of hardware for performing various functions.

2. Functional Units of Computer

3. Computer Software
Computer software is the set of programs that makes the hardware perform a set of tasks in particular order. Hardware and software are complimentary to each other. Both have to work together to produce meaningful results. Computer software is classified into two broad categories; system software and application software System Software: System software consists of a group of programs that control the operations of a computer equipment including functions like managing memory, managing peripherals, loading, storing, and is an interface between the application programs and the computer. MS DOS (Microsoft’s Disk Operating System), UNIX are examples of system software Application software: Software that can perform a specific task for the user, such as word processing, accounting, budgeting or payroll, fall under the category of application software. Word processors, spreadsheets, database management systems are all examples of general purpose application software.

4. Computer Language
Computer language or programming language is a coded syntax used by computer programmers to communicate with a computer. Computer language establishes a flow of communication between software programs. The language enables a computer user to dictate what commands the computer must perform to process data. These languages can be classified into following categories.
1. Machine language
2. Assembly language
3. High level language

5. Operating System
An operating system is a software component of a computer system that is responsible for the management of various activities of the computer and the sharing of computer resources. It hosts several applications that run on a computer and handles the operations of computer hardware. Users and application programs access the services offered by the operating systems, by means of system calls and application programming interfaces. Users interact with a computer operating system through Command Line Interfaces (CLIs) or Graphical User Interfaces known as GUIs. In short, an operating system enables user interaction with computer systems by acting as an interface between users or application programs and the computer hardware. Some of the common operating systems are LINUX, Windows, etc.

6. Important functions of an operating System.
Memory Management
Processor Management
Device Management
File Management
Security
Control over system performance
Job accounting
Error detecting aids
Coordination between other software and
users

7. Batch System
Batch Systems • Introduction of tape drives allow batching of jobs: – programmers put jobs on cards as before. – all cards read onto a tape. – operator carries input tape to computer. – results written to output tape. – output tape taken to printer. • Computer now has a resident monitor : – initially control is in monitor. – monitor reads job and transfer control. – at end of job, control transfers back to monitor. • Even better: spooling systems. – use interrupt driven I/O. – use magnetic disk to cache input tape. – fire operator. • Monitor now schedules jobs. . .

8. Multi-Programming
Use memory to cache jobs from disk ) more than one job active simultaneously.
• Two stage scheduling:
1. select jobs to load: job scheduling.
2. select resident job to run: CPU scheduling.
• Users want more interaction ) time-sharing:
• e.g. CTSS, TSO, Unix, VMS, Windows NT. . .

9. Current OS
Single user systems: cheap and cheerful. – personal computers. – no other users ) ignore protection. – e.g. DOS, Windows, Win 95/98, • RT Systems: power is nothing without control. – hard-real time: nuclear reactor safety monitor. – soft-real time: mp3 player. • Parallel Processing: the need for speed. – SMP: 2–8 processors in a box. – MIMD: super-computing. • Distributed computing: global processing? – Java: the network is the computer. – Clustering: the network is the bus. – CORBA: the computer is the network. – .NET: the network is an enabling framework. . .

10. Monolithic Operating Systems
Oldest kind of OS structure (“modern” examples are DOS, original MacOS)
• Problem: applications can e.g.
– trash OS software.
– trash another application.
– hoard CPU time.
– abuse I/O devices.
– etc. . .
• No good for fault containment (or multi-user).
• Need a better solution. . .

11. Dual-Mode Operation
Want to stop buggy (or malicious) program from doing bad things.
Provide hardware support to distinguish between (at least) two different modes of operation:
1. User Mode : when executing on behalf of a user (i.e. application programs).
2. Kernel Mode : when executing on behalf of the operating system.
• Hardware contains a mode-bit, e.g. 0 means kernel, 1 means user.
• Make certain machine instructions only possible in kernel mode. . .

12. Operating System Functions
Regardless of structure, OS needs to securely multiplex resources: 1. protect applications from each other, yet 2. share physical resources between them. • Also usually want to abstract away from grungy harware, i.e. OS provides a virtual machine: – share CPU (in time) and provide each app with a virtual processor, – allocate and protect memory, and provide applications with their own virtual address space, – present a set of (relatively) hardware independent virtual devices, – divide up storage space by using filing systems, and – do all this within the context of a security framework. • Remainder of this part of the course will look at each of the above areas in turn. . .

13. MS-WORD 2000