Download Presentation

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
Hardware and Software Interaction: An
Overview
Software
 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)
 Controls hardware components that make up a
computer
 Provides an interface for users
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
 DOS
 Windows 9x
 Windows NT,
Windows 2000, and
Windows XP
 Unix
 Linux
 OS/2
 Mac OS
Categories of PC Software
 BIOS and device drivers
 Operating system
 Application software
Categories of PC Software
System Resources
System Bus Components
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
16-Bit ISA Bus
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
Second Interrupt Controller Chip on 16Bit ISA Bus
How IRQs Are Assigned
Accessing Device Manager to View
System Resources
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 Addresses
How the CPU Communicates Memory
Addresses
Division of Memory Under DOS
Assigning Memory Addresses
Shadowing ROM
 Process of copying programs from ROM to
RAM for execution
I/O Addresses
 Numbers the CPU can use to access hardware
devices
 Also called port addresses or ports
I/O Addresses
IRQs and I/O Addresses
continued…
IRQs and I/O Addresses
for Devices
DMA Channels
 Provide a shortcut for a device to send data
directly to memory, bypassing the CPU
How an OS Relates
to 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 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
Protected Mode
Real Mode and Protected Mode
Compared
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

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
 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 BIOS
How an OS Uses System BIOS
How Device Drivers Control Hardware
 Stored on the hard drive
 Usually written for a particular OS
Device Drivers
Device Drivers
Windows 9x Device Drivers
Device Drivers under
Windows 2000
 Uses only 32-bit drivers
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
 From the Start menu
 Shortcut icon on the desktop
 Run dialog box
 Windows Explorer or My Computer
Using a Shortcut Icon
Using the Run Dialog Box to Execute
Software
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