2. Chapter Objectives In this chapter, you will learn:
About operating systems and their key functions
How system resources help hardware and software communicate
About the steps in the boot process
How to use Device Manager and System Information to examine the system
Chapter 2: How Hardware and Software Work Together

3. Introducing Operating Systems
An operating system (OS) is software that contains instructions that coordinate all the activities among computer hardware resources
Chapter 2: How Hardware and Software Work Together

4. Operating System Components
Every operating system has two main internal components:
A shell is the portion of the OS that relates to the user and to applications
The kernel is the part that loads when you first turn on your computer
The Windows operating system uses a database called the registry to store hardware and software configuration information, user preferences, and application settings that are used when the OS is first loaded
Some data is kept in text files called initialization files
Chapter 2: How Hardware and Software Work Together

5. Operating System Components
Chapter 2: How Hardware and Software Work Together

6. Types of Operating Systems
DOS (Disk Operating System)
Windows
Unix
Linux
OS/2
Mac OS
Chapter 2: How Hardware and Software Work Together

7. An OS Provides a User Interface
With a command-line interface, you type commands or press specific keys to enter data and commands to instruct the OS to perform operations
A menu-driven interface provides menus as a way to enter data and commands
With a graphical user interface (GUI), you issue commands by selecting icons, buttons, windows, or other graphical objects on the screen
Chapter 2: How Hardware and Software Work Together

8. An OS Manages Files and Folders
Chapter 2: How Hardware and Software Work Together

9. An OS Manages Applications
Installing and Loading Application Software
Chapter 2: How Hardware and Software Work Together

10. An OS Manages Applications
Handling Multiple Programs
Single tasking vs. Multitasking
For an operating system to support multitasking, the CPU must be running in protected mode
In protected mode, the CPU processes 32 bits of data at one time
In real mode, the CPU processes 16 bits of data at one time
With preemptive multitasking, the operating system allots CPU time to an application for a specified period, and then preempts the processing to give the CPU to another application
Chapter 2: How Hardware and Software Work Together

11. An OS Manages Hardware
Chapter 2: How Hardware and Software Work Together

12. How an OS Uses Device Drivers
Chapter 2: How Hardware and Software Work Together

13. How an OS Uses Device Drivers
Installing a device in a system that supports Plug and Play usually is a simple process
With Plug and Play (PnP), if you connect a device to your computer, the operating system recognizes that hardware has been changed since the last time the computer was started or while the computer was running
PnP is not entirely foolproof
Manufacturers often update device drivers to address bugs or provide additional features
Chapter 2: How Hardware and Software Work Together

14. How an OS Uses System BIOS to Manage Devices
Chapter 2: How Hardware and Software Work Together

15. System Resources
A system resource is a tool used by either hardware or software to communicate its requirements
There are four types of system resources:
Interrupt requests (IRQs)
Memory addresses
I/O addresses
Direct Memory Access (DMA) channels
Chapter 2: How Hardware and Software Work Together

16. System Resources
Chapter 2: How Hardware and Software Work Together

17. System Resources
All four system resources depend on certain lines on a bus on the motherboard
Chapter 2: How Hardware and Software Work Together

18. Interrupt Requests (IRQs)
When a hardware device needs the CPU to do something, it uses a hardware interrupt
The device initiates a hardware interrupt by placing voltage on the designated interrupt request (IRQ) line assigned to it
On motherboards, part of the chip set called the interrupt controller manages the IRQs for the CPU
Only 8 IRQs were supported by the interrupt controller on early motherboards. A second interrupt controller was later added, which communicates with the CPU through the first interrupt controller, and handles an additional 8 IRQs
Polling software constantly runs and has the CPU periodically check a hardware device to see if it needs service
Chapter 2: How Hardware and Software Work Together

19. Interrupt Requests (IRQs)
Chapter 2: How Hardware and Software Work Together

20. Interrupt Requests (IRQs)
Chapter 2: How Hardware and Software Work Together

21. Memory Addresses
An operating system relates to a memory location by using a memory address, a number that always uses 0 as its first digit
Chapter 2: How Hardware and Software Work Together

22. I/O Addresses
I/O addresses, also called port addresses or just ports, are numbers the CPU can use to access hardware devices
The address bus on the motherboard carries memory addresses and I/O addresses
If the address bus has been set to carry I/O addresses, then each device listens to this bus. If the address belongs to it, then it responds. Otherwise it ignores the request for information
Chapter 2: How Hardware and Software Work Together

23. I/O Addresses
Chapter 2: How Hardware and Software Work Together

24. I/O Addresses
Chapter 2: How Hardware and Software Work Together

25. DMA Channels
A direct memory access (DMA) channel lets an I/O device send data directly to memory, bypassing the CPU
A chip on the motherboard contains the DMA logic and manages the process
Chapter 2: How Hardware and Software Work Together

26. Booting Up Your Computer
The process of starting or restarting a computer and loading the operating system is referred to as the boot process or booting
When you turn on a computer that is powered off completely, you are performing a cold boot, or hard boot
A warm boot, or soft boot, is the process of restarting a computer that already is powered on
Uses the operating system to reboot
A cold boot is slower and more stressful on your machine
Chapter 2: How Hardware and Software Work Together

27. Startup BIOS Controls the Beginning of the Boot
The functions performed during the boot can be divided into four parts:
Startup BIOS runs a process called the power-on self test and assigns system resources
The ROM BIOS startup program searches for and loads an OS
The OS configures the system and completes its own loading
Application software is loaded and executed
Chapter 2: How Hardware and Software Work Together

28. Startup BIOS Controls the Beginning of the Boot
Chapter 2: How Hardware and Software Work Together

29. POST and Assignment of System Resources
System clock begins to generate clock pulses
CPU initializes and begins working
CPU turns to ROM BIOS Startup program
CPU runs POST
POST checks BIOS program and CMOS RAM
Test for battery failure
Hardware interrupts are disabled
Tests are run on the CPU
Check to determine if this is a cold boot
Hardware devices installed are inventoried
Video card is tested and configured
POST checks RAM
Keyboard is checked
Some devices enter sleep mode
DMA and interrupt controllers are checked
CMOS setup runs if requested
BIOS begins its search for an OS
Chapter 2: How Hardware and Software Work Together

30. How the BIOS Finds and Loads the OS
Once POST and the first pass at assignment of resources are complete, the next step is to load an OS
Startup BIOS looks to CMOS setup to find out which device is set to be the boot device
Chapter 2: How Hardware and Software Work Together

31. How the BIOS Finds and Loads the OS
Chapter 2: How Hardware and Software Work Together

32. Loading the Core of Windows XP
Chapter 2: How Hardware and Software Work Together

33. Loading the Core of Windows XP
Files needed to boot Windows XP, Windows 2000, or Windows NT successfully
Chapter 2: How Hardware and Software Work Together

34. Troubleshooting the Boot Process
A successful boot depends on the hardware, the BIOS, and the operating system all performing without errors
If a system will not boot, you may need to try to boot the computer from a floppy disk
A floppy disk with enough software to load an operating system is called a boot disk, or recovery disk
A boot disk with some utility programs to troubleshoot a failed hard drive is called a rescue disk, emergency startup disk (ESD), or startup disk
It is important to have a rescue disk available in case of emergency
These can be created in the operating sytem
Chapter 2: How Hardware and Software Work Together

35. Operating System Tools to Examine a System: Device Manager
Using Windows XP, Windows 2000, and Windows 9x, Device Manager is the primary tool used to manage hardware devices
The Device Manager will also show how the IRQs are assigned on your computer
If a device is problematic, you can use Device Manager to review the properties for that device, or update the driver
Chapter 2: How Hardware and Software Work Together

36. Operating System Tools to Examine a System: Device Manager
Chapter 2: How Hardware and Software Work Together

37. Operating System Tools to Examine a System: System Information
The System Information utility provides more detailed information than that provided by Device Manager
The System Information utility lists:
The BIOS version
The directory where the OS is installed
How system resources are used
Information about drivers and their current status
The System Information utility allows you to save or print a report listing system information
Chapter 2: How Hardware and Software Work Together

38. Operating System Tools to Examine a System: System Information
Chapter 2: How Hardware and Software Work Together

39. Chapter Summary In this chapter, you learned:
About operating systems and their key functions
How system resources help hardware and software communicate
About the steps in the boot process
How to use Device Manager and System Information to examine the system
Chapter 2: How Hardware and Software Work Together

40. Chapter 2 Complete