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DOS with Windows 3.1 and 3.11 Operating Environments

Designed to allow applications to have a graphical interface• DOS runs in the background as the true

OS and uses Windows 3.x as the middle layer between the application and DOS

Has been replaced with Windows 9x

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DOS with Windows 3.x

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Windows 95 and 98

Do not completely eliminate DOS Windows 95

• Windows for Workgroups (Windows 3.11) plus DOS 7.0

• Introduced Plug and Play capability Windows 98

• Supports larger hard drives and more hardware devices

• Includes more software utilities• Faster than Windows 95• The last Microsoft OS with a DOS foundation

Windows 9x

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UNIX

Originally written for mainframe computers in the early 1970s

Now a popular OS for networking Linux

• A variation of UNIX that is free to everyone

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UNIX

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Windows NT

Completely eliminates the underlying relationship with DOS

Supports preemptive multitasking and multiprocessing

Designed to work within a powerful networked environment (client/server)

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Windows NT

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Windows 2000

A suite of operating systems, each designed for a different sized computer system• Windows 2000 Professional• Windows 2000 Server• Windows 2000 Advanced Server• Windows 2000 Datacenter Server

Built on Windows NT architecture Designed to ultimately replace both Windows

9x for low-end systems and Windows NT for midrange and high-end systems

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Windows 2000

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OS/2

Written by IBM in cooperation with Microsoft Corporation

Provides an altogether different OS in place of DOS

Slow to gain popularity due to:• Errors in earlier versions• Large computer hardware requirements

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OS/2

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Macintosh Operating System

Available only on Macintosh computers Offers easy access to the Internet Allows any Macintosh computer to

become a Web server for a small network

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Macintosh Operating System

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How an Operating System Manages an Application

DOS naming conventions• Filename (up to 8 characters)• File extension (3 characters)

Memory addressing under DOS

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Operating System Modes

Real mode• Single-tasking operating mode whereby programs:

Only have 1024K of memory addresses Have direct access to RAM Use a 16-bit data path

Protected mode• Supports multitasking whereby:

The OS manages memory Programs have more than 1024K of memory addresses Programs can use a 32-bit data path

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Real Mode

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Protected Mode

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Applications Software

Designed to work on top of a particular OS

Comes written on floppy disks or CD-ROMs; usually must be installed on a hard drive in order to run

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Categories of Applications Software

Word processing Spreadsheet Database management Graphics Communications Games Mathematical modeling Software development tools

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How Applications Software is Loaded and Initialized

1. OS receives command to execute application2. OS locates program file for the application3. OS loads program file into memory4. OS gives control to the program5. Program requests memory addresses from OS

for its data6. Program initializes itself; it may request that

data from secondary storage be loaded into memory

7. Program turns to user for its first instruction

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How Applications Software is Loaded and Initialized

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How Applications Software is Loaded and Initialized

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Launching a Program File

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Rules DOS Uses to Search for Executable Program Files

1. If no path is given before the filename, DOS looks in the current directory

2. If no path is given and the file is not in current directory, DOS looks in paths given to it by the last PATH command executed

3. If there is a path given in front of filename in the command line, DOS looks in that path

4. If there is a path given but the file is not found in that path, DOS looks in paths given to it by the last PATH command executed

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Copying the Program into Memory

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Loading Application Software Using Windows 9x

Place shortcut icon directly on desktop Click Start button; select Programs;

select program from list of installed software

Use Run command, after clicking Start button on the taskbar

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Loading Application Software Using Windows 9x

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Loading Application Software Using Windows 9x

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Applications Software Summary

Applications software is executed by either the operating environment (Windows 3.x) or the OS software (DOS or Windows 9x)

When an application is executing, you are interacting with the application

Applications software interacts with OS software that is executing it

OS software interacts with hardware OS software might interact with the hardware

through BIOS or the device driver

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Chapter Summary

Individual components that make up a computer system: hardware and software

Hardware• Devices used for input, output, processing, and

storage of data• Components that make up the electrical system• Components used for communicating data and

instructions from one device to another Importance of buses on the system board

continued

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Chapter Summary

CPU• Central processing point for all data and

instructions• Both data and instructions must be stored

in memory with assigned memory addresses before processing can begin

continued

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Chapter Summary

Software• Works in layers

Lowest layer (BIOS and device drivers) interfaces with hardware

Highest layer (applications software) interfaces with user

• OS is the middleman layer that coordinates everything