Chapter 2: Installing and Configuring Input Devices

Exam Objectives

Understanding keyboards

Working with the mouse

Modems and network cards

Other input devices

Understanding system resources

A computer’s job is to process information, but only after someone inputs that information into the system. In this chapter, I discuss different types of devices used to input data into the computer.

At anyone’s disposal are many forms of input devices with which you can communicate with the computer, such as modems, network cards, touch pads, and biometric devices. A keyboard and a mouse, though, are the most popular.

Minding Your Keys and Qs

The keyboard is the main device you use to interact with a computer system. Keystrokes are converted into the characters that you see onscreen, and maybe eventually print. Most keyboards have five major key parts, or groups, that contain keys grouped by specific purpose. These areas (standard desktop keyboard) are shown in Figure 2-1.

The five major groupings on a keyboard are

Alphanumeric: The alphanumeric keys are the keys on the keyboard that contain the letters of the alphabet, numerals, and punctuation.

Function: The 12 function keys on a keyboard offer special features. For example, in Windows, pressing F2 renames a file or icon.

Cursor: Use the cursor keys to move the cursor or insertion point.

Numeric: The numeric keypad has the mathematical operators and numbers for quick, single-handed access for inputting numeric information.

LEDs: The LEDs indicate whether features such as Caps Lock, Num Lock, and Scroll Lock are turned on or off.

Each key on the keyboard has a keyswitch that closes an electrical circuit on a grid when a key is pressed. When the key contacts the grid, the keyboard controller detects the keystroke and generates a keycode. The keycode is then converted into an ASCII code that is used to display the character onscreen.

Each location on the grid corresponds to a specific keycode. This is why you can’t simply move a keycap and expect to move the character as well. For example, the letter A is on the left side of the keyboard. Simply moving the A keycap to the right side of the keyboard will not allow you to press that key to type the letter A because the location on the grid that generates a keycode for letter A is on the left side of the keyboard.

Different keyboards work in different ways when you press a key. Each manufacturer decides what type of keyboard to manufacture and how the keystrokes will be interpreted by the system. The two most popular techniques used to identify what keys are being pressed are

Switch-based: Uses micro-switches for each key. The keys deteriorate with time and tend to get dirty, but these keyboards are inexpensive.

Capacitive: Also known as membrane keyboards and are more expensive than switch-based keyboards. Despite their higher cost, though, capacitive keyboards are more reliable. Each key pushes a spring, which pushes a paddle to create an impression on the capacitive surface located under the keyboard. The impression on the capacitive surface sends a signal that is interpreted by the keyboard controller. This is the most common type of keyboard in laptops and netbooks.

For a keyboard to work with a system, software must be employed that drives the keyboard actions. Two types of software routines are used to allow the keyboard to work with the system:

Keyboard device driver: Like any piece of hardware, a driver in Windows is responsible for allowing the device to work in Windows — including the keyboard.

Firmware: The keyboard firmware is typically stored in ROM in the actual keyboard (as in the case of an XT keyboard) or in a chip on the motherboard. The firmware contains low-level code to communicate with the hardware.

Identifying keyboard types

A number of different types of keyboards have been used over time. The following list identifies the different types of keyboards you need to know for the A+ Certification exam:

XT keyboard: The older XT keyboard has 83 alphanumeric keys, including 10 function keys. This keyboard has the keyboard processor located on the keyboard itself. In addition to the alphanumeric keys, it has a numeric keypad and cursor control keys on the right side of the keyboard.

AT keyboard: The older AT keyboard has 84 regular keys (an extra System Request key was added), and also features 10 function keys. The AT keyboard has a bigger Enter key than the XT keyboard, and the keyboard processor moved from the keyboard itself to the computer’s motherboard. The AT keyboard uses an AT keyboard connector, which is also known as a DIN-5 connector.

Enhanced keyboard: The enhanced keyboard is the popular keyboard used today, with 101 keys and 12 function keys. The enhanced keyboard has a numeric keypad along with cursor control keys located on the right side. The enhanced keyboard typically uses the PS/2 connection (also known as a mini-DIN 6 connector) or a USB connection.

Windows keyboard: A Windows keyboard is similar to an enhanced keyboard containing 101 keys, but the Windows keyboard contains buttons, or keys, that control features of Windows. For example, a Windows keyboard features a button to bring up the Start menu and also a key to bring up the shortcut menu (as if you had right-clicked with the mouse).

Natural, or ergonomic, keyboards: Natural, or ergonomic, keyboards are a modification of the enhanced keyboards. A natural keyboard separates the alphanumeric keys into two parts: one part for the left hand and the other for the right hand. The keyboard is bowed and might even come apart to allow for more natural hand placement. These keyboards normally also have a wrist rest to help hands sit in a more natural position. These keyboards are designed to reduce repetitive stress injuries. Figure 2-2 shows a typical natural keyboard.

Installing a keyboard

Installing a keyboard is fairly straightforward. You pretty much plug just the keyboard into the system, and Windows uses a keyboard driver to communicate with the device.

For the A+ exam, know the different keyboard connectors, as described in the following list:

DIN-5 connector: A DIN connector — also known as an AT connector — is used on older systems to connect the keyboard to the computer. You can always tell the DIN connector because it is large and round.

PS/2 connector: A PS/2 connector — also known as a mini-DIN 6 connector — has been the most popular keyboard connector found on computers in the past but has been replaced by the USB connector. It is identical to what is found on a typical mouse.

Figure 2-3 compares a DIN-5 connector beside a PS/2 connector.

USB connector: Keyboards that connect to the system via a USB connector have become very popular. A number of systems today are getting away from the PS/2 connections for keyboards and mice and using USB. Figure 2-4 shows a keyboard being connected to a USB port.

Configuring keyboards and setting accessibility options

Configuring a keyboard in Windows doesn’t involve a lot of options. Typically, you just plug it in, and it works. Windows does allow you to configure the blink rate of the cursor and also change the repeat rate, which dictates how quickly a letter will repeat if you hold down a key on your keyboard.

To configure the keyboard options, follow these steps:

1. XP: Choose Start⇒Control Panel⇒Printer and Other Hardware⇒Keyboard.

Windows 7/Vista: Choose Start⇒Control Panel⇒Hardware and Sound⇒Keyboard.

The Keyboard Properties dialog box appears, as shown in Figure 2-5.

2. Adjust the settings to suit your needs.

Here, you can configure the character repeat options and the cursor blink rate. The following options are available:

• Repeat Delay: Repeat delay controls the length of time between when you first hold down a key and when the character begins to repeat onscreen.

• Repeat Rate: Repeat rate controls how quickly additional characters are displayed when the key is held down.

• Cursor Blink Rate: Cursor blink rate controls how fast the cursor blinks.

3. Click OK to apply your settings and close the dialog box.

A number of accessibility features are available in Windows that are controlled via the keyboard. Accessibility features in Windows are designed for users who have disabilities. To configure the keyboard accessibility options, follow these steps:

1. XP: Choose Start⇒Control Panel⇒Accessibility Options.

The Accessibility Options dialog box appears, as shown in Figure 2-6.

Windows 7/Vista: Choose Start⇒Control Panel⇒Ease of Access⇒Ease of Access Center⇒Make the Keyboard Easier to Use.

2. Ensure that the Keyboard tab is selected and then configure the following options as needed:

• StickyKeys: This feature aids folks with an issue pressing two keys at the same time, such as Ctrl+C. Here is how it works (with StickyKeys enabled). When you press the Shift, Ctrl, or Alt key — or, if you have a Windows keyboard, the Windows key — that key remains active, as if you were holding it down, while you choose the next keystroke. If you press a key, such as the Shift key, twice then the key stays on until you press it again. Because pressing the key keeps the key held after you let go, if you wanted to perform a keystroke operation such as Ctrl-Alt-Delete with sticky keys you would simply press Ctrl, then press Alt and finally press the Delete key on its own.

• FilterKeys: Use FilterKeys to tell Windows to ignore repeated keystrokes. For example, if you hold down a key too long with FilterKeys enabled, the repeat rate of the keystroke is reduced. This prevents a character from appearing many times at a quick rate.

• ToggleKeys: Enabling the ToggleKeys option triggers audible tones when the Caps Lock, Num Lock, or Scroll Lock keys are pressed.

3. Click OK.

Catching the Mouse

The other popular input device found on computer systems today is the mouse. The mouse is one of the primary input devices because of the graphical user interface (GUI) features of today’s operating systems. The following sections identify the different types of mice and how to install them.

Types of mice

You can find three types of mice on today’s desktop computer systems: mechanical mice, opto-mechanical mice, and optical mice.

Mechanical: A mechanical mouse was the only type of mouse used with computers for many years. The mechanical mouse uses a rubber ball that moves a pair of wheels inside the mouse. The internal wheels capture the horizontal and vertical movements of the mouse and then send that information to the computer. The movement is then displayed onscreen.

Opto-mechanical: The opto-mechanical mouse is a very popular mouse today. It uses a rubber ball that moves rollers that control the movement of a disc — the encoding disc — which has holes along the side of it.

The prefix “opto” comes into play because LEDs and sensors use an infrared light beam to determine the movement of the mouse. See Figure 2-7. When the rubber ball moves the encoding disc, the infrared beam passes through the holes on the encoding disc, indicating that the mouse has moved and in which direction.

Optical: An optical mouse differs from an opto-mechanical mouse because an optical mouse has no moving parts. The rubber ball and wheels are replaced with an optical scanning system that works on pretty much any surface.

The optical scanning system is made up of optical sensors and a Digital Signal Processor (DSP). An optical mouse captures images of the surface at a rate of 1,500 images per second. The DSP then analyzes and compares the images to detect the mouse movement.

Installing a mouse

Installing a mouse is very similar and just as easy as installing a keyboard. You pretty much just plug in the mouse, and the Windows mouse driver controls the device. The following is a list of the different types of interfaces you may use to connect a mouse to the system:

Serial: A serial mouse connects to the serial port on the computer. The serial port is the male 9-pin or 25-pin port on the back of the computer that sends data one bit at a time. Serial mice are not as popular as they once were.

PS/2: One of the most popular interfaces for a mouse on desktop computers is a PS/2 connection. A PS/2 connection is also known as a mini-DIN 6 connector.

USB: The most popular type of connection for mice today is the USB connector. Simply plug the mouse into the USB port and click away! As you find out in many chapters of this book, USB is hot-swappable — meaning that you can plug and unplug a USB device without shutting down the system. USB can transfer data at 12 Mbps (USB 1.1) or 480 Mbps (USB 2.0).

More and more, today’s systems are using wireless keyboards and mice, which use a USB wireless adapter that connects to the computer that is responsible for receiving the signals from the wireless keyboard or mouse. The wireless signal is sent through radio frequency or via infrared depending on the keyboard or mouse. For more information on wireless, check out Book VIII, Chapter 2.

Communicating with Modems and Network Adapters

In this section, you find out about installing modems and network cards that allow computer systems to communicate with other systems on the network.

Working with modems

A modem is a communication device that modulates, or converts, the digital signal from the computer into an analog signal so that it can travel over an analog line, such as telephone wire. The signal is then demodulated back into a digital signal at the modem on the receiving system. The process of modulating and demodulating is where the amalgam word modem comes from.

A modem allows a computer to send data over an analog line and is useful when you want to dial up another computer over a phone line or access the Internet.

Modem characteristics

A modem is either internal or external:

An internal modem is installed in an expansion slot within the computer housing as either an older ISA card or, more popular today, a PCI card.

An external modem sits on the desk beside the computer and plugs into the computer’s serial port.

Both internal and external modems plug into a telephone jack via a standard telephone cable.

Another very important characteristic of the modem is its speed. The speed of the modem is measured in bits per second (bps) — and like anything else, the more bits the better! When it comes to modem speed, you’re looking at 56 Kbps (56,000 bps) as the standard. This is known as a 56K modem.

AT commands

For the A+ exam, you need to be familiar with what an AT command is. AT is short for ATtention, and AT commands are the modem commands that are called by software to perform communication. You typically don’t need to use these commands unless you’re troubleshooting why a computer cannot dial up. Your first question is always, “Is it the modem or the application I am using?” By using these low-level AT commands, you can determine whether the modem is working.

The AT commands that you should be comfortable with for the A+ exam are listed in Table 2-1.

Table 2-1 AT Modem Commands

Command	Description
ATDT <number>	Dial a number using touch-tone dialing.
ATDP <number>	Dial a number using pulse or rotary dialing.
ATA	Instruct the modem to answer.
ATH	Instruct the modem to hang up.
ATL	Set the speaker loudness.
ATZ	Reset the modem to the default settings.

Here are sequential-hint tricks to remembering these commands for the A+ exam.

1. Each command starts with the AT prefix

2. Then you have a character, such as D for dial, A for answer, or H for hang-up. The “L” stands for loudness and the “Z” is used for default ­settings.

3. Because there are two types of dial tones, the dial command has another character representing the type of dial tone to use and requires the telephone number to dial.

For example, to call my friend Ed’s house with touch-tone dialing, the AT command would be

ATDT 555-5555

Okay, this isn’t Ed’s phone number. He wouldn’t like it too much if I put his personal phone number in the book. But you get the idea of how the command works. There are more AT commands than just what I show here, but these are the ones you need to be familiar with for the exam.

Installing a modem

Most modems today ship as PCI cards and are inserted into a PCI slot in the computer: the very definition of an internal modem. You can install an internal modem by following these steps:

1. Power-off the computer and be sure to ground yourself.

2. Remove the cover from the computer.

3. If necessary, remove the blanking plate that allows access to the modem from the back of the PC.

This allows the modem card to fit in the slot.

4. Place the modem card into the appropriate expansion slot.

For example, you will most likely have a PCI card, so place the PCI modem card into an available PCI slot.

5. Screw the modem card into place and put the cover back on the PC.

6. The modem has two ports on it that both take RJ-11 connections. Connect the incoming phone line to the appropriate port and then connect the phone to the modem’s second port.

7. Power-on the PC.

Configuring a modem

After you install the modem and Windows starts up, Plug and Play should kick in and detect the new device. If a driver is not present in Windows for the device, you will be asked for the driver. If you do not have the driver, you can choose to cancel adding the driver at this time and go to Device Manager at a later time to update the driver after you have it. See Book VI, Chapter 1, to find out how to load and configure drivers via Device Manager.

When the driver is loaded, you can go to the properties of the device in Device Manager and query the modem to verify that the modem is functioning properly. In short, querying the modem describes sending AT commands to the modem and verifying that the modem responds to the commands. The nice thing is that you don’t need to type each command listed earlier in Table 2-1; use the Query button in the properties of the modem to do this for you. To verify that the modem is working, follow these troubleshooting steps:

1. In Windows XP, click Start and right-click My Computer.

In Windows 7/Vista, click Start and right-click Computer.

2. Choose Properties from the pop-up menu.

3. In Windows XP, in the System Properties window, click the Hardware tab and then click the Device Manager button.

In Windows 7/Vista, in the System Properties window, click the Device Manager link from the Tasks list on the left side.

4. In Device Manager, expand the modems node, right-click your modem, and then choose Properties.

5. In the Properties window of the modem, click the Diagnostics tab (shown in Figure 2-8) and then click the Query Modem button to perform a diagnostic on your modem using the AT commands.

You should notice a list of AT commands that have been issued against the modem as a diagnostic test and whether the test was successful.

6. Close all windows.

Working with network adapters

The most popular communication device found in computers today is a network card. A network card is a device that allows you to connect your computer to a network or the Internet, and is responsible for sending and receiving data on the network. Not only are network cards popular in systems found in the corporate world, but because of the popularity of high-speed Internet, you can also find them in a lot of home computers as well.

Network cards are categorized by their transfer rates. For example, a network card that can transfer 100 million bits of data per second is a 100 Mbps network card, and a network card that can transfer 1000 million bits per second is a 1000 Mbps network card.

The card will run at the highest common speed available between the two communicating devices. For example, if you connect your system to a 100 Mbps network switch but your system has a 1000 Mbps network card, your card will run at only 100 Mbps. This is why most systems have what is called a 100/1000 network card — the card can talk at either 100 Mbps or 1000 Mbps.

Installing a network adapter (card)

When installing a network card, you first need to determine what type of interface you wish to use. There are a number of types of network cards that could be installed into the system. For example, you could install a USB network card, an old ISA card for older computers, or the more popular PCI network card (shown in Figure 2-9) that is inserted into a PCI slot.

To install a network adapter, follow these steps:

1. Power-off the computer and be sure to ground yourself.

2. Remove the cover from the computer.

3. If necessary, remove the blanking plate that allows access to the modem from the back of the PC.

This allows the network card to fit in the slot.

4. Place the network card into the appropriate expansion slot.

For example, you will most likely have a PCI card, so place the PCI network card into an available PCI slot.

5. Screw the network card into place and put the cover back on the PC.

6. Connect the network cable to the back of the network card.

7. Power-on the PC.

Configuring a network card

After you install the network card, Plug and Play should kick in and either load the driver for you or prompt you for the driver. When the driver is loaded, you can specify settings for the network card in Windows. For example, if you want to force your network card to run at a particular speed, you can do that through the properties of the network card.

To configure your network card in XP, follow these steps:

1. Click Start and right-click My Computer.

2. Choose Properties from the pop-up menu.

3. In the System Properties window, click the Hardware tab and then click the Device Manager button.

4. In Device Manager, expand the Network Adapters category on the left, right-click your network card, and then choose Properties.

5. In the Properties dialog box for the network card, click the Advanced tab to see settings that can be configured for the network card (shown in Figure 2-10).

The advanced settings are different for each make and model of network card because the settings are particular to the driver that is loaded. A very popular setting is the link speed, which specifies what speed you wish to run the card at. Most network cards are set to Auto, which means the card will detect the best speed. When troubleshooting, though, you can force a particular speed.

Typically, you may also choose which type of connector on the network card will be used — if it has multiple connector styles. For example, a number of network cards ship with both an RJ-45 port and a BNC (bayonet-type) port — this is called a combo card. If you want to ensure that the system is using the RJ-45 port, you set that in the device properties.

To configure the network card in Windows 7/Vista, you perform the same steps with the exception of how you start Device Manager. To start Device Manager in Windows 7/Vista

1. Click the Start button.

2. Right-click the Computer menu item and choose Properties.

3. In System properties, click the Device Manager link in the tasks list on the left side of the screen.

After Device Manager launches, you can change the settings the same way as mentioned earlier in Windows XP by going to the network card properties.

Other Input Devices

As technology moves on, new input devices appear. For example, laptops use a touch pad as an input device, whereas hand-held devices use a pen-like stylus. The following is a list of input devices you might encounter:

Touch pad: A number of laptop systems today use a touch pad as an alternative way to control the mouse pointer in Windows. The touch pad — that rectangular area found below the keyboard that you move your finger(s) across to move the mouse pointer — also usually bears two buttons below the square to perform left- and right-click operations. A touch pad is displayed in Figure 2-11.

Touch screens: You see touch screens used a lot at public terminals for things like information booths and bank machines. Touch screens require that you actually touch the screen to choose different options.

Bar code reader: A bar code reader is a type of scanner that reads bar codes and then converts the bar code into data stored on a computer and used in applications. An inventory application is an example of an application that uses a bar code reader as an input device.

Biometric devices: Biometric devices are used to authenticate, or log, people onto a system by using biological characteristics of that person, such as a fingerprint or a retinal scan. Biometric devices are very popular in high-security environments because of how difficult it is to impersonate someone when dealing with authentication methods such as a fingerprint scan. Some laptop makers are even starting to include fingerprint scanners in consumer-level laptops as security devices and theft deterrents.

Scanner: A scanner is used to capture the contents of a document or real-life object and generate an image of the object on the computer that is connected to the scanner. You find out more about scanners in Book III, Chapter 5.

KVM: A KVM switch is a device that allows you to connect a single keyboard, mouse, and monitor to the KVM switch. The KVM switch is then connected to multiple computers so that you can use the one set of keyboard, mouse, and monitor to switch among multiple computers.

I use this in my office because I have three computers but do not want to have to physically use three different keyboards, mice, and monitors. I simply press the toggle button on the KVM switch and it changes which computer I am viewing on the screen and managing with the keyboard and mouse.

Microphone: The microphone is used to create audio input on the system. The microphone is connected to the microphone port on the system and can be used with recording software to record your voice.

Game pads and joysticks: A game pad is also known as a control pad and is a device similar to a controller for a video game console like an Xbox or PlayStation. Just as those controllers allow you to navigate through the games on a console, a game pad can provide input to a computer as well. Another common input device with games on the computer is the joystick: a device that has a stick used to navigate and typically has a button on the base.

Digitizer: A digitizer is a device that is used to create a digital form of information that is not on the computer. For example, if you have some old books or documents, you can create electronic documents out of them with a digitizer. You can also find digitizers to convert old reel-to-reel movies, VHS movies, and cassette tapes to electronic files.

This chapter has discussed installing a network card into the system, but a number of other types of cards can be installed. The process to install any kind of expansion card into the system is the same as installing a network card. The following are other types of expansion cards you may need to install:

Serial and parallel cards: You can install a card in the system that has serial ports or parallel ports on the back of the card. This is typically referred to as an I/O card.

USB cards: If you are running out of USB ports on the system, you can install an expansion card that has additional USB ports on the back to allow you to connect USB devices to the computer.

FireWire cards: If your system did not come with FireWire ports and you have a device such as a digital video camera that uses FireWire, you will need to install a FireWire card in the system that has the appropriate ports.

Storage cards: Many computers today have a way to connect storage cards or memory cards to the system. If your system did not come with card readers, you can purchase and install a storage card reader to allow you to insert different types of memory cards.

Modem cards: You read about modems earlier. If your system did not come with a modem and you need one, you can purchase an internal modem and install it in an expansion slot.

Wireless/cellular cards: Just as you can add a network card to the system for a wired network, you can also install a wireless network card in the system to get wireless network access or cellular network access.

Riser cards: A riser card is connected directly to the motherboard and “rises up” from the motherboard. It is its own board that has a number of expansion slots on it so that you can add other types of cards to the system.

Understanding System Resources

As far as this chapter is concerned, when you see the term system resource, think of it as a setting assigned to a device that allows it to function within the computer. A device is any piece of hardware that you can install on the computer, for example, a network card, modem, or sound card.

The three major system resources that can be assigned to devices are I/O addresses, IRQ addresses, and DMA addresses. A fourth system resource — a memory address — can sometimes be assigned to devices as well. In the following sections, I discuss each of these system resources.

I/O addresses

The CPU (processor) is the traffic cop of the entire system. If something is going to happen on the system, the CPU usually enables the action. All devices in the computer need to communicate with the processor from time to time, and the processor needs a method of separating and prioritizing all these communications.

Because the processor needs to send information to a number of different devices, and because those devices need to know which messages coming from the CPU are for them, each device is assigned an I/O (input/output) address. The I/O address is a special port address that represents a pathway between the CPU and the device. So, for example, if the processor needs to send information to LPT1, it can send the information to pathway 0378–037F, which is the pathway address that leads to LPT1. (For more on the standard I/O address assignments, see Table 2-2, later in this chapter.) Think of these pathways as tunnels; each device has its own tunnel that extends from the device to the processor and is used for communication between the device and the processor.

Figure 2-12 shows a number of devices that are configured with I/O addresses. (Note that the addresses in the figure are not necessarily the actual addresses that are used by those devices. I made up these addresses simply to get the point across.) In this example, if the processor needs to send information to the sound card, it knows that if it sends the information down I/O port address 220, the sound card will receive the information. Conversely, when the processor receives information from I/O port address 220, it knows that the information came from the sound card because the address of 220 is assigned to only one device — the sound card!

There are 65,536 different I/O port addresses available on a system. (Actually fewer usable addresses than that are available, because when you assign an I/O address to a device, you are really assigning a range of addresses.) The trick to troubleshooting system resources is to make sure that you do not assign the same I/O port address to two different devices. If you do, you get a resource conflict — two devices using the same resource, such as an I/O address, an IRQ, or a DMA channel.

The I/O address assigned to a device is really a range of values, such as 0378–037F. Most people refer to the address block by the first value in the range, in this example, 0378.

To prevent resource conflicts, each device should have a unique I/O address. But how do you know which I/O addresses are already being used by existing devices? One way is to use Device Manager to view I/O addresses being used on the system.

When troubleshooting Windows XP, you can use Device Manager to obtain a list of resources in use. To view I/O addresses in use with these operating systems, follow the steps below:

1. Click Start.

2. Right-click My Computer and choose Properties.

3. Click the Hardware tab.

4. Click the Device Manager button.

5. Choose View⇒Resources by Type.

The screen should look similar to the one shown in Figure 2-13.

6. Expand Input/Output (I/O) and view the list of I/O addresses being used (shown in Figure 2-14).

To navigate to the Device Manager program in Windows 7/Vista, follow similar steps:

1. Click Start.

2. Right-click Computer and choose Properties.

3. Click the Device Manager link on the left in the task list.

4. Choose Continue from the User Account Control dialog box.

5. In Device Manager, choose View⇒Resources by Type.

The A+ Certification exams used to test heavily on the different I/O addresses, but you are no longer required to know them for the exam. Table 2-2 lists the I/O addresses for general knowledge and your reference.

Table 2-2 Standard I/O Address Assignments

Device	I/O Address Range
COM1	03F8–03FF
COM2	02F8–002FF
COM3	03E8–003EF
COM4	02E8–002EF
LPT1	0378–0037F
LPT2	0278–0027F
Math coprocessor	00F8–000FF
Primary hard disk controller	01F0–001F7
Secondary hard disk controller	0170–00177
Sound cards	0220–0022F
Floppy disk	03F0–003F7

Interrupt request (IRQ)

Each device has its own tunnel for sending and receiving information to and from the processor, which is the function of the I/O port address discussed in the previous section. But the processor is busy doing something important nearly all the time. How does the processor know when a device has information to communicate to the processor? Too much overhead would be created if the processor had to continuously poll each device to see whether it had data to send to the processor; instead, each device is responsible for notifying the processor if it has information to send. Because devices are responsible for notifying the processor that they have information, the devices need a way to interrupt the processor from its current work to ask it to service their requests. The method that is used to interrupt the processor is an interrupt request (IRQ) line.

If you were standing beside someone involved in a conversation and you really wanted to talk to that person, what would you do? Most people would tap the person on the shoulder and say something like, “Excuse me, sir, can I send you data?” Okay, maybe you wouldn’t say that, but you get the idea. Tapping the person on the shoulder is similar to what a device does with the processor when it wants to send the processor some information. The device sends a signal down the IRQ line, which virtually taps the processor on the shoulder. As a result, the device grabs the processor’s attention, and the processor is ready to receive information via the I/O address.

When a device taps the processor on the shoulder, the processor needs to know which device needs attention. This is why each device is assigned a unique IRQ line number. When a device sends a signal down the IRQ line to interrupt the processor, the processor checks which line the signal originated from and then attends to that device. For example, in Figure 2-15 (remember that the values shown in the figure are for discussion purposes only — use Table 2-3, later in this section, to find out which IRQs are used by devices). In this example, if the network card wants to send information to the processor, the network card must first get the processor’s attention by sending a signal down IRQ 10. Once the network card has the processor’s attention it is ready to send it information.

When information is sent to the processor, it is sent through the I/O address (the tunnel), not the IRQ line. The IRQ just grabs the processor’s attention, but the I/O address is used for the actual delivery of the information.

Cascading IRQs

Originally only eight IRQs were available on XT (before 286) systems, but now, 16 IRQs are available on AT (after 286) systems. To get 16 IRQs, another IRQ controller was added to the system. Having two sets of IRQs managed by two different controllers presented some technical problems, so to help the two IRQ controllers act as one unit, they are cascaded (linked) together by IRQ 2 and IRQ 9. The second controller goes through the first controller to send requests. Figure 2-16 shows the two controllers linked.

Here is how cascading controllers work. In Figure 2-16, the path that the math coprocessor (which uses IRQ 13) takes to send an interrupt request to the processor is shown in three steps:

1. The math coprocessor attempts to send a signal to the CPU. However, because the second interrupt controller handles the math coprocessor, the signal is passed to IRQ 9, which forwards all signals for the second interrupt controller.

2. IRQ 9 passes the signal to its linked partner, IRQ 2, which is managed by the first interrupt controller.

3. IRQ 2 then passes the signal through the first interrupt controller, which then sends the signal to the CPU.

Because older systems only had one set of eight IRQs, when the additional eight IRQs came along, only the first interrupt controller was allowed to send information to the CPU. This means that when interrupts 8 through 15 send an interrupt request, they must pass it to the first controller, which in turn passes it to the processor on their behalf.

Like I/O addresses, if you assign two devices the same IRQ value, you get a resource conflict that results in at least one (and maybe both) of the devices not working. To prevent assigning two devices the same resource, you need to understand which IRQ values are already being used by your system.

To view a list of IRQs in use on a Windows XP or Windows Server 2003 system, follow these steps:

1. Right-click My Computer and choose Properties.

2. Click the Hardware tab.

3. Click the Device Manager button.

4. Choose View⇒Resources by Type.

5. Expand Interrupt Request (IRQ) and view the list of IRQs being used.

The screen should look similar to the one shown in Figure 2-17.

Because of the low number of IRQs available on a system, Intel has been incorporating a newer technology in its new processors: Advanced Programmable Interrupt Controller (APIC). Intel currently has APIC supporting up to 24 IRQs.

Viewing the list of IRQs in Windows 7/Vista is very similar. You need to locate the Device Manager by choosing Start, right-clicking Computer, and then choosing Properties. When you are in the System Properties, click the Device Manager link in the Tasks section on the left side. When you are in Device Manager, choose View⇒Resources by Type to view the system resources, such as I/O addresses and IRQs.

Table 2-3 shows a listing of the standard IRQs and their use. You do not need to memorize this table for the A+ Certification exams.

Table 2-3 Standard IRQ Assignments

IRQ Value	Device
0	System timer
1	Keyboard
2	Link to second IRQ controller
3	COM2, COM4
4	COM1, COM3
5	LPT2
6	Floppy disk drive
7	LPT1
8	Real-time clock
9	Available, but should not be used if IRQ 2 is being used
10	Available
11	Available
12	Available if not used by PS/2 mouse
13	Math coprocessor
14	Hard disk controller
15	Available

The lower the IRQ value, the higher the priority the device will have with the processor. Here are a few important points about IRQ assignments:

IRQs 10, 11, 12, and 15 are generally available. If you are installing a new device into a computer and need to assign an IRQ, try one of these IRQ values first.

IRQ 3 and IRQ 5 are used by COM2 and LPT2, respectively. If you are not actually using COM2 or LPT2, you can consider IRQ 3 and IRQ 5 as being available.

When discussing IRQs, I like to ask, “What is the IRQ of a modem plugged into a COM port?” Know that an IRQ is not really assigned to a modem when it is plugged into a COM port but rather the COM port the modem is using is assigned the resource. You will also want to have an idea of where infrared and USB devices will sit as far as IRQs are concerned. Infrared ports attach themselves to virtual COM or LPT ports, which means that your infrared device will probably end up using IRQ 3 or 4. USB ports use the IRQ associated with the PCI bus, which can be anywhere from IRQ 9 on up.

Direct memory access (DMA)

A number of different devices today require constant access to system memory. Normally, devices must go through the CPU to write information to system memory, but using such a scheme can cause a lot of unnecessary overhead, so why not allow a device to access memory directly?

To increase performance and to offload some of the work from the CPU, you can assign some devices a direct memory access (DMA) channel. A DMA channel is a special pathway that allows the device to read and write information directly to system memory without passing the data to the processor.

For example, in Figure 2-18, you can see that the modem has been assigned DMA channel 6 and the printer has been assigned DMA channel 5. (Like I/O addresses, these addresses may be different on each system. The values I use in the figure are fictitious.) In this example, the modem and the printer can write information to memory directly, whereas the network card and the sound card must pass through the CPU.

Only eight DMA channels are available on your system, which should not be a huge problem because not all devices use DMA channels. Some examples of the different devices that you might run into that use DMA channels are sound cards, network cards, and occasionally CD-ROM drives. Table 2-4 shows a listing of common DMA channels.

Table 2-4 Common DMA Channel Assignments

DMA Channel	Device
0	Available
1	Sound or Available
2	Floppy drive
3	Available
4	Cascade
5	Sound or Available
6	Available
7	Available

Like IRQs, two DMA controllers are linked by a cascading DMA channel: DMA channel 4. DMA channels 0–3 are used for 8-bit boards and cards; DMA channels 5–7 are used for 16- and 32-bit cards.

To view the DMA channels in use on your system, you can use the Windows Device Manager utility. The following steps demonstrate how to view the DMA channels in use within Windows XP and Windows Server 2003 systems:

1. Right-click My Computer and choose Properties.

2. Click the Hardware tab.

3. Click the Device Manager button.

4. Choose View⇒Resources by Type.

5. Expand Direct Memory Access (DMA) and view the list of DMA channels being used (shown in Figure 2-19).

Viewing the list of DMA channels in Windows 7 or Windows Vista is very similar. You need to locate the Device Manager by choosing Start, right- clicking Computer, and then choosing Properties. When you are in the System Properties, click the Device Manager link in the Tasks section on the left side. When you are in Device Manager, choose View⇒Resources by Type to view the system resources, such as DMA channels, I/O addresses, and IRQs.

Memory addresses

A less common resource that might be assigned to devices is a memory address, which is an area of memory where the device is allowed to store information.

If multiple devices have been assigned access to the same memory address, a device conflict will occur, and one or both devices might not function. When troubleshooting devices, you need to look out for memory address conflicts. The following steps demonstrate how to view memory addresses in use within XP and Windows Server 2003:

1. Right-click My Computer and choose Properties.

2. Click the Hardware tab.

3. Click the Device Manager button.

4. Choose View⇒Resources by Type.

5. Expand Memory and view the list of memory addresses being used (shown in Figure 2-20).

Viewing the list of DMA channels in Windows 7 or Windows Vista is very similar. You need to locate the Device Manager by choosing Start, right-­clicking Computer, and then choosing Properties. When you are in the System Properties, click the Device Manager link in the Tasks section on the left side. When you are in Device Manager, choose View⇒Resources by Type to view the system resources, such as memory addresses.

It is important to note that today you will typically not work with I/O addresses, IRQs, and DMA channels because the devices are automatically assigned these through plug-and-play (PNP). PNP is a big feature of today’s hardware and operating systems that allows the system to assign these resources automatically. It was not always this way. I remember years ago running software that came with the network card that allowed me to change the resources. The challenge was trying to find a resource that was not already in use.

The information presented in this chapter on system resources is only here so that you understand the terminology when you hear the terms. The A+ exams no longer expect you to memorize all the system resources, and you realistically may never need to try to change a resource setting unless you are working with much older hardware.

Getting an A+

In this chapter, you find out about different types of input devices. The following list outlines some of the key points to remember for the exam:

Keyboards usually connect to the system with a PS/2 connection or a USB connection with today’s systems.

Older keyboards use a DIN-5 to connect to the motherboard.

Most mice today connect to the system via a USB port or a PS/2 port.

A serial mouse connects to the serial port, but this type of mouse isn’t very common anymore.

Modems are used to convert digital signals to analog and vice versa so that digital data can be delivered over an analog line.

Network cards are the most popular type of communication device in today’s systems. Be sure to review the networking chapters to fully understand how to network a system.

Know that when you install hardware in the system that the hardware uses system resources such as an IRQ, I/O address, and possibly a DMA channel. Also, know that those resources are assigned through plug-and-play, which means that the OS detects the hardware and assigns these resources automatically.

Prep Test

1 Which two formats do serial ports come in?

A 9-pin

B 15-pin

C 20-pin

D 25-pin

2 At what speed does USB 1.1 transfer information?

A 10 Mbps

B 12 Mbps

C 100 Mbps

D 480 Mbps

3 Which type of keyboard is designed to reduce repetitive stress injuries?

A AT keyboard

B Natural keyboard

C Windows keyboard

D Enhanced keyboard

4 Which type of mouse uses a rubber ball and sensors connected to two wheels to determine mouse movement?

A Mechanical

B Opto-mechanical

C Optical

D Wheel

5 What is the AT command to hang up the connection?

A ATDT

B ATA

C ATH

D ATDP

6 At what speed does USB 2.0 transfer information?

A 10 Mbps

B 12 Mbps

C 100 Mbps

D 480 Mbps

7 Which two popular connector types are used with a mouse?

A USB

B Parallel

C PS/2

D OS/2

8 Which two types of interfaces are typically used to connect a network card to the system?

A Parallel

B USB

C PCI

D Serial

9 What is the AT command to call 555-5555?

A ATDT 555-5555

B ATA 555-5555

C ATH 555-5555

D ATZ 555-5555

10 What type of input device is used by a warehousing application to take inventory of all the products?

A Touch pad

B Touch screen

C Touch mouse

D Bar code reader

Answers

1 A, D. Serial ports, which are used by serial mice, come in two formats: 9-pin and 25-pin. See “Installing a mouse.”

2 B. USB 1.1 devices run at 12 Mbps, and USB 2.0 devices run at 480 Mbps. Review “Installing a mouse.”

3 B. Natural keyboards are a form of ergonomic keyboard that reduces repetitive stress injuries. Check out “Identifying keyboard types.”

4 A. A mechanical mouse uses all moving parts, such as a rubber ball that moves wheels that are picked up by sensors to detect mouse movements. Peruse “Types of mice.”

5 C. The AT command used by modems to hang up a connection is ATH — the H stands for hang up. Take a look at “AT commands.”

6 D. USB 2.0 runs at 480 Mbps, and USB 1.1 runs at a lower speed of 12 Mbps. Peek at “Installing a mouse.”

7 A, C. Popular connections used by the mouse today are the USB connector and the PS/2 connector. Look over “Installing a mouse.”

8 B, C. Network cards connect to the system as either a USB or PCI device. Study “Installing a network adapter (card).”

9 A. The ATDT command is used to dial a number. Refer to “AT commands.”

10 D. A bar code reader is a type of device that reads bar codes and converts the code into data to be used on the computer. Examine “Other Input Devices.”