A+ Guide to Managing
and Maintaining Your PC
Fifth Edition
Chapter 2
How Hardware and Software
Work Together
You Will Learn…

About operating systems, what they are, and
what they do

How an OS interfaces with users, applications,
and hardware

How system resources help hardware and
software communicate
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Introducing Operating Systems

Software that controls a computer

Acts as a middleman between applications and
hardware

Two main internal components

Shell

Kernel
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OS as a Middleman
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The Shell and the Kernel
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Common Operating Systems







DOS
Windows 9x
Windows NT, Windows 2000, and
Windows XP
Unix
Linux
OS/2
Mac OS
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What an Operating System
Does

Provides user interface

Stores, retrieves, and manipulates files and
folders

Manages applications

Manages hardware
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How an OS Provides a User
Interface

Command-driven interfaces

Menu-driven interfaces

Icon-driven interfaces
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A Menu-Driven Interface
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How an OS Manages Files and
Folders

Uses file system (FAT or NTFS) to track how
clusters are used for each stored file

Uses directories, subdirectories, and files

Uses partitions and logical drives on hard drive
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Tracks, Sectors, and Clusters
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Files and Directories
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Partitions and Logical Drives
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How an OS Manages
Applications

Provides access to hardware resources

Manages data in memory and in secondary
storage

Performs other background tasks
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Loading Application Software
Using the Windows Desktop

Shortcut icon

Start menu

Run command

Windows Explorer or My Computer
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Using a Shortcut Icon to Load
Software
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Real and Protected Operating
Modes


Real (16-bit) operating mode

CPU processes 16 bits of data at one time

Software has “real” access to hardware
Protected (32-bit) operating mode

CPU processes 32 bits of data at one time

More than one program can be running, each one
“protected” from others

Uses preemptive multitasking
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16-Bit and 32-Bit Software


16-bit software

Written for Windows 3.x

Accesses data 16 bits at a time

Programs should not infringe on resources of other
programs that are running
32-bit software

Written for Windows 95 and later Windows OSs
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How an OS Manages Hardware

Uses device drivers or the BIOS (system
BIOS, startup BIOS, or CMOS setup) to
interface with hardware

Trend is to manage devices with device drivers
rather than BIOS
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How an OS Manages Hardware
(continued)
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How an OS Uses Device
Drivers to Manage Hardware

Device drivers provide OS with software
necessary to control devices

16-bit read-mode drivers


Supported by Windows 95/98
32-bit protected-mode drivers

Supported by Windows 95/98, Windows Me, and
Windows NT/2000/XP
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How an OS Uses System BIOS
to Manage Devices

To communicate with simple devices (eg,
floppy drives or keyboards)

To access the hard drive
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Using System BIOS
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Using System BIOS (continued)
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System Resources
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System Resources (continued)

Depend on certain lines on a bus on
motherboard

System bus components

Data bus carries data

Address bus communicates addresses (memory
addresses and I/O addresses)

Control bus controls communication (IRQs and
DMA channels)
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System Bus Components
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Interrupt Request Number (IRQ)

Line on a bus that device needing service uses
to alert the CPU

Managed by interrupt controller on
motherboard

Early motherboards: eight IRQs

Second group of IRQs and second interrupt
controller have been added to accommodate need
for more devices
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Common Assignments for First
Eight IRQs
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Second IRQ Controller
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Viewing IRQ Assignments

Microsoft Diagnostic Utility (MSD) for DOS

Device Manager for Windows 2000/XP and
Windows 9x
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Viewing IRQ Assignments
(continued)
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Viewing IRQ Assignments
(continued)
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Memory Addresses

Hexadecimal numbers assigned to RAM and
ROM so the CPU can access both

Used to access physical memory

Often written in segment:offset form
(eg, C800:5)
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Memory Addresses (continued)
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I/O Addresses

Numbers CPU can use to access hardware
devices
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I/O Addresses (continued)
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Common Assignments for I/O
Addresses
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Direct Memory Access (DMA)
Channels

Shortcut method that lets an I/O device send
data directly to memory, bypassing the CPU
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DMA Channels
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OS Tools to Examine a System

Device Manager

System Information utility

Microsoft Diagnostic Utility (MSD)
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Device Manager

Primary tool used to manage hardware devices
under Windows 2000/XP and Windows 9x
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Device Manager ( continued)
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System Information Utility

Gives similar, but more, information than
Device Manager

BIOS version in use

Directory where OS is installed

How system resources are used

Information about drivers and their status

Additional information about software
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Using Windows System
Information
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Microsoft Diagnostic Utility
(MSD)

Useful for viewing information about the
system, including:

Memory

Video

Ports

Device drivers

System resources
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Using MSD
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Summary

How hardware and software work together

Different operating systems


What they do

How they work to control hardware devices
How an OS provides the interface that users
and applications need to command and use
hardware devices
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