Computer Memory and Operating Systems

Session 3

Memory and Operating System

Session Objectives

• Explain the concept of computer memory
• Describe the logical structure of computer memory
• List the different units for measurement of computer memory
• Explain the concept of operating system

Describe EDP cycle in detail

Session Objectives [Contd…]

• Describe the CPU Architecture.
• Describe about the CPU registers
• Name the categories of operating system
• Explain the features of GUI systems

List the features of an OS

Archie, please return My $1000

• Which money Tom,
• I can’t remember!!!

Need for Memory

Computer Memory

The capacity of the computer to store data at an instant and its ability to retrieve the same data at another point of time is termed as the computer memory.

• Memory is used to store both data and information

Computer’s memory can be visualized as a contiguous block of rectangular holes.

Visualisation of Computer Memory

• Look at the Shelf Tom,
• Cell
• Block of Memory

Contents(Data or Information)

Dictionary of Bits and Bytes

Data given by the user is either decimal numbers or alphabets. So, a step of conversion is necessary before the inputs get accepted by the computer.

Hey!!! I can understand only 0s and 1s

Dictionary of Bits and Bytes contd…

• 2
• Numbers and alphabets get converted into binary numbers
• 0 1 0

Bit(Binary Digit)

Conversion program

Dictionary of Bits and Bytes contd…

• 8 Bits= 1 Byte
• 1 TB

1024MB=1GB

• 1024 KB=1MB
• 1024 Bytes= 1KB

Tera Byte

Introduction To Operating System

Office Environment

• I want the Year End financial report !!

Yes Sir,

Introduction To Operating System contd…

• User
• Take these numbers and give me their sum.
• OS
• Ok Sir, It will be done

Computer Environment

Definition of OS

OS is a system software which acts as an interface between the user and the computer hardware.

Functions of Operating System

• Booting
• loads the user program into the computer memory
• The data required by the program is also loaded into the memory.

Gives instruction to the computer to display the result on the monitor

Functions of Operating System [Contd…]

Provides the means for the proper use of the resources like input,output and storage devices.

Thus it acts as a manager of various computer resources.

Functions of Operating System [Contd…]

The operating system software controls the computer hardware. It co-ordinates the flow of data from the storage unit to the processor and vice versa.

Therefore

An OS is responsible for forwarding the inputs to the processor, get the computation done, and display the result This process is popularly also known as the EDP cycle.

EDP CYCLE

• INPUT

DEVICES

• CPU

BUFFER

OUTPUT DEVICES

PRIMARY MEMORY

Components of the CPU

• CPU

CPU Registers

This unit is for storing any data that comes into the CPU while processing.

ALU

The Arithmetic and Logic Unit or the ALU takes care of all the mathematical and logical Operations to be done during calculations.

Control Unit (CU)

This unit controls the whole process of data transfer from one place to the other while computations are going on

Classification Of Operating Systems

• Operating Systems can be categorized into two types.

Single User Operating System

• Example: MS DOS
• User

Processor

Classification Of Operating Systems [Contd…]

Multi – User Operating System

A computer system, when acts as an interface for more than one user, it becomes a multi user environment system Example: Windows -NT

Classification Of Operating Systems [Contd…]

• 4
• OS is carrying User1’s Work to the processor
• I have some work for you Mr. OS
• The OS puts User2’s work in queue
• I have some work for you Mr. OS
• 1
• USER1
• USER2
• 3
• 5
• User’s 1 job can be collected back and hence User2’s work is taken up
• 6
• Processor
• OS

2

OTHER CLASSIFICATION OF OS

By Device & Use Case

• Desktop/Laptop OS: Windows, macOS, Linux (Ubuntu, Fedora), ChromeOS.
• Mobile OS: Android, iOS (for iPhones/iPads).

Server OS: Linux distributions (Ubuntu Server, Red Hat), Windows Server.

Embedded OS: For specialized devices like smart TVs, cars, ATMs (often proprietary or stripped-down Linux/RTOS).

Real-Time OS (RTOS): Critical for precise timing, used in medical devices, robotics, automotive systems (e.g., VxWorks, QNX).

By Functionality

Multi-Tasking: Runs multiple applications at once (Windows, macOS, Linux).

Multi-User: Allows multiple users to access the system simultaneously (Linux, Windows Server).

• Time-Sharing: Divides CPU time among users for quick response (modern multitasking OS).
• Distributed: Manages multiple computers as one system over a network.
• Network OS (NOS): Manages network resources and communication.

Batch OS: Processes jobs in batches without direct user interaction (older systems).

Modern ExamplesOF OS

• Windows: Most popular on desktops, known for broad software compatibility.

macOS: Apple's OS for Macs, known for user experience and ecosystem integration.

Linux: Open-source, dominant in servers and supercomputers, many variations (distributions).

• Android: Open-source, highly customizable, powers most smartphones.

iOS: Apple's mobile OS, known for security and simplicity on iPhones/iPads.

Graphical User Interface Systems

• OS which use pictures on its interface to
• abstract functionalities are GUI(Graphical

user Interface) OS

Hence the user can just point and select appropriate pictures to invoke the required functionality of the OS Example :

Windows OS : Win ’95 and Win NT.

Components Of GUI System

Desktop

This is an area on the screen, which displays the various components of a GUI. It is always the starting screen to the OS environment.

Components Of GUI System [Contd…]

Desktop

Components Of GUI System [Contd…]

Windows

Every group under a GUI operating system has a number of icons. These are enclosed in a frame called window

Menu Bar

• The menu bar at the top of the display which shows the various menu options.

Menu Pad

Menu Bar

Components Of GUI System [Contd…]

• Menu
• Menus hold a list of commands that usually are related in some way
• Menu options

Ellipses

Components Of GUI System [Contd…]

Menu Options

• The menu options are displayed as a list when the user selects the menu

Ellipse

An ellipse indicates that the command will display a dialog box to make additional choices and complete the data for the command execution

Components Of GUI System [Contd…]

• Toggle
• Some commands are preceded by a check mark as Save settings on exit
• Check marks are on/off indicators. They are called toggle options

Dialog Boxes

They are used to choose options for the commands…

Components Of GUI System [Contd…]

• Check box

List Box

Text Box

Radio button

Components Of GUI System [Contd…]

List Boxes

• The list box contains more than one option, which can be traversed by the scroll bar

Text Boxes

• It shows an insertion point to enter the text

Radio Buttons

only one item from the group is to be selected

Components Of GUI System [Contd…]

Control Menu

Every window has a control menu, which has menu options to maximize, minimize or resize a window. In addition, it has options to close the window

Session Summary

Memory is the capability of a computer to store and retrieve data.

Bit is the basic unit of computer memory measurement and tera byte is the largest amongst the memory measurement units today.

OS is an agent that facilitates the execution of user defined job from the computer.

Session Summary

• OS can be either single user or multi user.

GUI features have gained popularity for the OS.