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Chapter 2. How Hardware and Software Work Together. You Will Learn…. How hardware and software interact How system resources help hardware and software communicate How an OS relates to BIOS, device drivers, and applications Different ways an OS can launch applications.

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Chapter 2

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Chapter 2

Chapter 2

How Hardware and Software Work Together

You will learn

You Will Learn…

  • How hardware and software interact

  • How system resources help hardware and software communicate

  • How an OS relates to BIOS, device drivers, and applications

  • Different ways an OS can launch applications

Hardware and software interaction an overview

Hardware and Software Interaction: An Overview



  • The intelligence of the computer

  • Determines what hardware is present

  • Decides how it is configured and used

  • Uses hardware to perform tasks

Operating system os

Operating System (OS)

  • Controls hardware components that make up a computer

  • Provides an interface for users

Functions of an os

Functions of an OS

  • Uses BIOS

  • Manages secondary and primary storage

  • Helps diagnose problems with hardware and software

  • Interfaces between hardware and software

  • Performs tasks the user requests

Available operating systems


Windows 9x

Windows NT, Windows 2000, and Windows XP




Mac OS

Available Operating Systems

Categories of pc software

Categories of PC Software

  • BIOS and device drivers

  • Operating system

  • Application software

Categories of pc software1

Categories of PC Software

System resources

System Resources

System bus components

System Bus Components

The 8 bit and 16 bit isa slots

The 8-Bit and 16-Bit ISA Slots

  • 8-bit ISA bus

    • Older bus used on early PCs (1980s)

    • Had eight lines for data

  • 16-bit

    • Provide more memory addresses, DMA channels, and IRQs

8 bit isa bus

8-Bit ISA Bus

16 bit isa bus

16-Bit ISA Bus

Interrupt request number irq

Interrupt Request Number (IRQ)

  • Line on a bus that a device needing service uses to alert the CPU

  • COM and LPT are preconfigured assignments of system resources that a device can use

Irq numbers

IRQ Numbers

Second interrupt controller chip on 16 bit isa bus

Second Interrupt Controller Chip on 16-Bit ISA Bus

How irqs are assigned

How IRQs Are Assigned

Accessing device manager to view system resources

Accessing Device Manager to View System Resources

Memory addresses

Memory Addresses

  • Number assignments for memory locations

  • Hexadecimal numbers, often written in segment:offset form, assigned to RAM and ROM so that the CPU can access both

  • Example: C800:5, which is 819,205 in decimal

Memory addresses1

Memory Addresses

How the cpu communicates memory addresses

How the CPU Communicates Memory Addresses

Division of memory under dos

Division of Memory Under DOS

Assigning memory addresses

Assigning Memory Addresses

Shadowing rom

Shadowing ROM

  • Process of copying programs from ROM to RAM for execution

I o addresses

I/O Addresses

  • Numbers the CPU can use to access hardware devices

  • Also called port addresses or ports

I o addresses1

I/O Addresses

Irqs and i o addresses

IRQs and I/O Addresses


Irqs and i o addresses for devices

IRQs and I/O Addressesfor Devices

Dma channels

DMA Channels

  • Provide a shortcut for a device to send data directly to memory, bypassing the CPU

How an os relates to other software

How an OS Relatesto Other Software

  • All interaction between software and hardware is by way of the CPU

  • CPU operates in two modes:

    • 16-bit (real mode)

    • 32-bit (protected mode)

  • OS must use same mode the CPU uses

Real 16 bit and protected 32 bit operating modes

Real (16-Bit) and Protected (32-Bit) Operating Modes

  • Real mode

    • Single-tasking

    • 16-bit data path; 1 MB of memory addresses

  • Protected mode

    • Multitasking

    • 32-bit data data path; at least 4 GB of memory addresses

    • OS manages access to RAM and does not allow a program direct access to it

Real mode

Real Mode

Protected mode

Protected Mode

Real mode and protected mode compared

Real Mode and Protected Mode Compared

How an os uses real and protected modes

How an OS Uses Real and Protected Modes

  • OS must be in sync with the CPU

  • Applications must be compiled to run in either real or protected mode

  • Hybrid of real and protected mode used by older software written for Windows 3.x

General types of software that run on pcs

General Types of Software That Run on PCs

  • 16-bit DOS software

    • Designed to run in real mode as only program running and expecting direct access to hardware

  • 16-bit Windows software

    • Designed for Windows 3.x to run where other programs might also be running

  • 32-bit Windows software

    • Designed to run in protected mode with other software and can be loaded into extended memory

How an os uses system bios

How an OS Uses System BIOS

  • Contains programming instructions to run simple hardware devices (eg, keyboard and floppy disk drive)

  • Can be used to access the hard drive

  • Stored on ROM chips

How an os uses system bios1

How an OS Uses System BIOS

How an os uses system bios2

How an OS Uses System BIOS

How device drivers control hardware

How Device Drivers Control Hardware

  • Stored on the hard drive

  • Usually written for a particular OS

Device drivers

Device Drivers

Device drivers1

Device Drivers

Windows 9x device drivers

Windows 9x Device Drivers

Device drivers under windows 2000

Device Drivers underWindows 2000

  • Uses only 32-bit drivers

How an os launches applications

How an OS Launches Applications

  • Applications depend on an OS to:

    • Provide access to hardware resources

    • Manage its data in memory and secondary storage

    • Perform many background tasks

Loading application software using the windows desktop

Loading Application Software Using the Windows Desktop

  • From the Start menu

  • Shortcut icon on the desktop

  • Run dialog box

  • Windows Explorer or My Computer

Using a shortcut icon

Using a Shortcut Icon

Using the run dialog box to execute software

Using the Run Dialog Box to Execute Software

Chapter summary

Chapter Summary

  • How operating system software controls several significant hardware devices

  • How an OS provides the interface that applications need to command and use hardware devices

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