Chapter 1: Introduction to the Personal Computer

1.0 Introduction

Information technology (IT) is the design, development, implementation, support, and management of computer hardware and software applications. An IT professional is knowledgeable about computer systems and operating systems. This chapter will review IT certifications and the components of a basic personal computer system.

After completing this chapter, you will meet these objectives:

• Explain IT industry certifications.
• Describe a computer system.
• Identify the names, purposes, and characteristics of cases and power supplies.
• Identify the names, purposes, and characteristics of internal components.
• Identify the names, purposes, and characteristics of ports and cables.
• Identify the names, purposes, and characteristics of input devices.
• Identify the names, purposes, and characteristics of output devices.
• Explain system resources and their purposes.

1.1 Explain IT industry certification

This course will focus on desktop and laptop computers. It will also discuss electronic devices, such as personal digital assistants and cell phones.

Training and experience will qualify a technician to service these computers and personal electronic devices. You will gain the specialized technical skills needed to install, maintain, and repair computers. Earning an industry standard certification will give you confidence and increase your opportunities in IT.

This course is focused on the following two industry standard certifications:

• The CompTIA A+
• The European Certification of Informatics Professional (EUCIP) IT Administrator Certification (Modules 1- 3)

After completing this section, you will meet these objectives:

• Identify education and certifications.
• Describe the A+ Certification.
• Describe the EUCIP Certification.

1.1.1 Identify education and certifications

Information Technology (IT) is a term that encompasses the relationship between hardware, software, networks, and technical assistance provided to users. IT Essentials: PC Hardware and Software covers the information that a technician needs to be successful in IT. This course covers the following topics:

• Personal computers
• Safe lab procedures
• Troubleshooting
• Operating systems
• Laptop computers
• Printers and scanners
• Networks
• Security
• Communication skills

The IT Essentials course focuses on two hardware and software skills-based industry certifications: CompTIA A+ and EUCIP. This course is only an introduction into the world of IT. A technician may continue to study and earn the following certifications:

• CCNA \x96 Cisco Certified Networking Associate
• CCNP \x96 Cisco Certified Networking Professional
• CCIE \x96 Cisco Certified Internetworking Expert
• CISSP \x96 Certified Information Systems Security Professional
• MCP \x96 Microsoft Certified Professional
• MCSA \x96 Microsoft Certified Systems Administrator
• MCSE \x96 Microsoft Certified Systems Engineer
• Network+ \x96 CompTIA Network Certification
• Linux+ \x96 CompTIA Linux Certification

IT certifications can be used as credits for university and college degrees in areas such as computer science and telecommunications.

1.1.2 Describe the A+ certification

Computing Technology Industry Association (CompTIA) developed the A+ Certification program. A CompTIA A+ certification, as shown in Figure 1, signifies that a candidate is a qualified PC hardware and software technician. CompTIA certifications are known throughout the IT community as one of the best ways to enter the information technology field and build a solid career.

The latest version of CompTIA A+ is CompTIA A+ 2009 Edition. Two exams are necessary to be certified: CompTIA A+ Essentials, exam code 220-701; and CompTIA A+ Practical Application, exam code 220-702.

CompTIA A+ Essentials measures the necessary competencies of an entry-level IT professional with at least 500 hours of hands-on experience in the lab or field. It tests for the fundamentals of computer technology, networking and security, as well as the communication skills and professionalism now required of all entry-level IT professionals.

CompTIA A+ Practical Application is an extension of the knowledge and skills identified in CompTIA A+ Essentials, with more of a hands-on orientation focused on scenarios in which troubleshooting and tools must be applied to resolve problems.

Worksheet: Job Opportunities

1.1.3 Describe the EUCIP certification

The EUCIP IT Administrator program offers a recognized certification of competence in IT. The certification covers the standards prescribed by the Council of European Professional Informatics Societies (CEPIS). The EUCIP IT Administrator Certification consists of five modules, with a corresponding exam for each module. This course will prepare you for Modules 1\x963.

Module 1: Computer Hardware

The Computer Hardware module requires that the candidate understand the basic makeup of a personal computer and the functions of the components. The candidate should be able to effectively diagnose and repair hardware problems. The candidate should be able to advise customers of appropriate hardware to buy.

Module 2: Operating Systems

The Operating Systems module requires that the candidate be familiar with the procedures for installing and updating most common operating systems and applications. The candidate should know how to use system tools for troubleshooting and repairing operating systems.

Module 3: Local Area Network and Network Services

The Local Area Network and Network Services module requires that the candidate be familiar with the procedure of installing, using, and managing local area networks. The candidate should be able to add and remove users and shared resources. The candidate should know how to use system tools for troubleshooting and repairing networks.

Module 4: Expert Network Use

This module is beyond the scope of the IT Essentials course, although some of the topics are covered. The Expert Network Use module requires that the candidate understand LAN communication.

Module 5: IT Security

This module is beyond the scope of the IT Essentials course, although some of the topics are covered. The IT Security module requires that the candidate be familiar with security methods and features that are available for a standalone or networked computer.

1.2 Describe a computer system

A computer system consists of hardware and software components. Hardware is the physical equipment such as the case, storage drives, keyboards, monitors, cables, speakers, and printers. The term software includes the operating system and programs. The operating system instructs the computer how to operate. These operations may include identifying, accessing, and processing information. Programs or applications perform different functions. Programs vary widely depending on the type of information that will be accessed or generated. For example, instructions for balancing a checkbook are very different from instructions for simulating a virtual reality world on the Internet.

The rest of this chapter discusses the hardware components found in a computer system.

1.3 Identify the names, purposes, and characteristics of cases and power supplies

The computer case provides protection and support for the internal components of the computer. All computers need a power supply to convert alternating-current (AC) power from the wall socket into direct-current (DC) power. The size and shape of the computer case is usually determined by the motherboard and other internal components.

You can select a large computer case to accommodate additional components that may be required in the future. Other users may select a smaller case that requires minimal space. In general, the computer case should be durable, easy to service, and have enough room for expansion.

The power supply must provide enough power for the components that are currently installed and allow for additional components that may be added at a later time. If you choose a power supply that powers only the current components, it may be necessary to replace the power supply when other components are upgraded.

After completing this section, you will meet these objectives:

• Describe cases.
• Describe power supplies.

1.3.1 Describe cases

A computer case contains the framework to support the internal components of a computer while providing an enclosure for added protection. Computer cases are typically made of plastic, steel, and aluminum and are available in a variety of styles.

The size and layout of a case is called a form factor. There are many types of cases, but the basic form factors for computer cases include desktop and tower. Desktop cases may be slimline or full-sized, and tower cases may be mini or full-sized, as shown in Figure 1. ((Types of Computer Cases))

Computer cases are referred to in a number of ways:

• Computer chassis
• Cabinet
• Tower
• Box
• Housing

In addition to providing protection and support, cases also provide an environment designed to keep the internal components cool. Case fans are used to move air through the computer case. As the air passes warm components, it absorbs heat and then exits the case. This process keeps the components of the computer from overheating.

There are many factors that must be considered when choosing a case:

• The size of the motherboard
• The number of external or internal drive locations called bays
• Available space

See Figure 2 for a list of features. ((Choosing a Case))

In addition to providing protection from the environment, cases help to prevent damage from static electricity. Internal components of the computer are grounded by attachment to the case.

NOTE: You should select a case that matches the physical dimensions of the power supply and motherboard.

1.3.2 Describe power supplies

((Figure 1 Power Supply))

The power supply, shown in Figure 1, converts alternating-current (AC) power coming from a wall outlet into direct-current (DC) power, which is a lower voltage. DC power is required for all of the components inside the computer.

A computer can tolerate slight fluctuations in power, but a significant deviation can cause the power supply to fail. An uninterruptible power supply (UPS) can protect a computer from problems caused by changes in power. A UPS provides power for a computer using a power inverter. A power inverter provides AC power to the computer from a built-in battery by converting the DC current of the UPS battery into AC power.

Connectors

Most connectors today are keyed connectors. Keyed connectors are designed to be inserted in only one direction. Each part of the connector has a colored wire with a different voltage running through it, as seen in Figure 2:

Power Color Code
Voltage	Wire Color	Use	Power Supply Forms
.	.	.	AT	ATX	ATXv12
+12V	Yellow	Diskdrive motors, fans, cooling devices and the system bus slots	*	*	*
-12V	Blue	Some types of serial port circuits and early programmable read only memory (PROM)	*	*	*
+3.3V	Orange	Most newer CPUs, some types of system memory and AGP video cards		*	*
+5	Red	Motherboard, Baby AT and earlier CPUs and many motherboard components	*	*	*
-5V	White	ISA bus cards and early PROMS	*	*	*
0V	Black	Ground - Used to complete circuits with the other voltages	*	*	*

Different connectors are used to connect specific components and various locations on the motherboard:

• A Molex connector is a keyed connector used to connect to an optical drive or a hard drive.
• A Berg connector is a keyed connector used to connect to a floppy drive. A Berg connector is smaller than a Molex connector.
• A 20-pin or 24-pin slotted connector is used to connect to the motherboard. The 24-pin slotted connector has two rows of 12-pins each, and the 20-pin slotted connector has two rows of 10-pins each.
• A 4-pin to 8-pin auxiliary power connector has two rows of two to four pins and supplies power to all areas of the motherboard. The 4-pin to 8-pin auxiliary power connector is the same shape as the main power connector, but smaller.
• Older standard power supplies used two connectors called P8 and P9 to connect to the motherboard. P8 and P9 were unkeyed connectors. They could be installed backwards, potentially damaging the motherboard or power supply. The installation required that the connectors were lined up with the black wires together in the middle.

NOTE: If you have a difficult time inserting a connector, try a different way, or check to make sure that there are no bent pins or foreign objects in the way. Remember, if it seems difficult to plug in any cable or other part, there is something wrong. Cables, connectors, and components are designed to fit together snugly. Never force any connector or component. The connectors that are plugged in incorrectly will damage the plug and the connector. Take your time and make sure that you are handling the hardware correctly.

Electricity and Ohm's Law

These are the four basic units of electricity:

• Voltage (V)
• Current (I)
• Power (P)
• Resistance (R)

Voltage, current, power, and resistance are electronic terms that a computer technician must know:

• Voltage is a measure of the force required to push electrons through a circuit.
• Voltage is measured in volts (V). A computer power supply usually produces several different voltages.
• Current is a measure of the amount of electrons going through a circuit.
• Current is measured in amperes, or amps (A). Computer power supplies deliver different amperages for each output voltage.
• Power is a measure of the pressure required to push electrons through a circuit, called voltage, multiplied by the number of electrons going through that circuit, called current. The measurement is called watts (W). Computer power supplies are rated in watts.
• Resistance is the opposition to the flow of current in a circuit. Resistance is measured in ohms. Lower resistance allows more current, and therefore more power, to flow through a circuit. A good fuse will have low resistance or a measurement of almost 0 ohms.

There is a basic equation that expresses how three of the terms relate to each other. It states that voltage is equal to the current multiplied by the resistance. This is known as Ohm's Law.

V = IR

In an electrical system, power (P) is equal to the voltage multiplied by the current.

P = VI

In an electrical circuit, increasing the current or the voltage will result in higher power.

As an example of how this works, imagine a simple circuit that has a 9 V light bulb hooked up to a 9-V battery. The power output of the light bulb is 100-W. Using the equation above, we can calculate how much current in amps would be required to get 100-W out of this 9-V bulb.

To solve this equation, we know the following information:

• P = 100 W
• V = 9 V
• I = 100 W/9 V = 11.11 A

What happens if a 12-V battery and a 12-V light bulb are used to get 100 W of power?

100 W / 12 V = 8.33 amps

This system produces the same power, but with less current.

Computers normally use power supplies ranging from 250W to 650W output capacity. However, some computers may need 850W and higher capacity power supplies. When building a computer, select a power supply with sufficient wattage to power all of the components. Each component inside the computer uses a certain amount of power. Obtain the wattage information for the components from the manufacturer's documentation. When deciding on a power supply, make sure to choose a power supply that has more than enough power for the current components. A power supply with a higher wattage rating has more capacity; therefore, it can handle more devices.

On the back of the power supply is a small switch called the voltage selector switch. This switch sets the input voltage to the power supply to either 110V / 115V or 220V / 230V. The correct voltage setting is determined by the country where the power supply will be used. Setting the voltage switch to the incorrect input voltage could damage the power supply and other parts of your computer. If a power supply does not have the voltage selector switch, your power supply will automatically detect and set the correct voltage.

CAUTION: Do not open a power supply. Electronic capacitors located inside of a power supply, shown in Figure 3, can hold a charge for extended periods of time.

((Figure 3: Netzteil von innen mit markierten Kondensatoren)

1.4 Identify the names, purposes, and characteristics of internal components

This section discusses the names, purposes, and characteristics of the internal components of a computer.

After completing this section, you will meet these objectives:

• Identify the names, purposes, and characteristics of motherboards.
• Explain the names, purposes, and characteristics of CPUs.
• Identify the names, purposes, and characteristics of cooling systems.
• Identify the names, purposes, and characteristics of ROM and RAM.
• Identify the names, purposes, and characteristics of adapter cards.
• Identify the names, purposes, and characteristics of storage drives.
• Identify the names, purposes, and characteristics of internal cables.

1.4.1 Identify the names, purposes, and characteristics of motherboards

The motherboard is the main printed circuit board and contains the buses, or electrical pathways, found in a computer. These buses allow data to travel between the various components that comprise a computer. Figure 1 shows a variety of motherboards. A motherboard is also known as the system board, the backplane, or the main board.

The motherboard accommodates the central processing unit (CPU), RAM, expansion slots, heat sink/fan assembly, BIOS chip, chip set, and the embedded wires that interconnect the motherboard components. Sockets, internal and external connectors, and various ports are also placed on the motherboard.

The form factor of motherboards pertains to the size and shape of the board. It also describes the physical layout of the different components and devices on the motherboard. The form factor determines how individual components attach to the motherboard and the shape of the computer case. Various form factors exist for motherboards, as shown in Figure 2: (Motherboard Form Factors)

Form Factors
AT	Advanced Technology
ATX	Advanced Technology Extended
Mini-ATX	Smaller footprint of Advanced Technology Extended
Micro-ATX	Smaller footprint of Advanced Technology Extended
LPX	Low-Profile Extended
NLX	New Low-Profile Extended
BTX	Balance technology Extended

The most common form factor in desktop computers was the AT, based on the IBM AT motherboard. The AT motherboard can be up to approximately one foot wide. This cumbersome size led to the development of smaller form factors. The placement of heat sinks and fans often interferes with the use of expansion slots in smaller form factors.

A newer motherboard form factor, ATX, improved on the AT design. The ATX case is designed to accommodate the integrated I/O ports on the ATX motherboard. The ATX power supply connects to the motherboard via a single 20-pin connector instead of the confusing P8 and P9 connectors used with some earlier form factors. Instead of using a physical toggle switch, the ATX power supply can be powered on and off using signaling from the motherboard.

Some manufacturers have proprietary form factors based on the ATX design. This causes some motherboards, power supplies, and other components to be incompatible with standard ATX cases.

An important set of components on the motherboard is the chipset. The chipset is composed of various integrated circuits attached to the motherboard that control how system hardware interacts with the CPU and motherboard. The CPU is installed into a slot or socket on the motherboard. The socket on the motherboard determines the type of CPU that can be installed.

The chipset of a motherboard allows the CPU to communicate and interact with the other components of the computer, and to exchange data with system memory, or RAM, hard disk drives, video cards, and other output devices. The chipset establishes how much memory can be added to a motherboard. The chipset also determines the type of connectors on the motherboard.

Most chipsets are divided into two distinct components, Northbridge and Southbridge. What each component does varies from manufacturer to manufacturer. In general, the Northbridge controls access to the RAM, video card, and the speeds at which the CPU can communicate with them. The video card is sometimes integrated into the Northbridge. AMD and Intel have chips that integrate the memory controller onto the CPU die, which improves performance and power consumption. The Southbridge, in most cases, allows the CPU to communicate with the hard drives, sound card, USB ports, and other I/O ports.

1.4.2 Identify the names, purposes, and characteristics of CPUs

The central processing unit (CPU) is considered the brain of the computer. It is sometimes referred to as the processor. Most calculations take place in the CPU. In terms of computing power, the CPU is the most important element of a computer system. CPUs come in different form factors, each style requiring a particular slot or socket on the motherboard. Common CPU manufacturers include Intel and AMD.

The CPU socket or slot is the connector that interfaces between the motherboard and the processor. Most CPU sockets and processors in use today are built around the pin grid array (PGA) architecture, in which the pins on the underside of the processor are inserted into the socket, usually with zero insertion force (ZIF). ZIF refers to the amount of force needed to install a CPU into the motherboard socket or slot. Slot-based processors are cartridge-shaped and fit into a slot that looks similar to an expansion slot. Figure 1 lists common CPU socket specifications: (CPU Types and Socket Specifications)

CPU Socket Specifications
Intel/AMD 486 class
Socket	Pins	Layout	Voltage	Supported Processors
Socket 1	169	17x17 PGA	5V	486 SX/SX2, DX/DX2, DX4 OD
Socket 2	238	19x19 PGA	5V	486 SX/SX2, DX/DX2, DX4 OD, 486 Pentium OD
Socket 3	237	19x19 PGA	5V/3.3V	486 SX/SX2, DX/DX2, DX4 OD, 486 Pentium OD, AMD 5x86
Socket 6	235	19x19 PGA	3.3V	486 DX4, 486 Pentium OD
Intel/AMD 586 (Pentium) class
Socket	Pins	Layout	Voltage	Supported Processors
Socket 4	273	21x21 PGA	5V	Pentium 60/66, OD
Socket 5	320	37x37 SPGA	5V/3.3V	Pentium 25-133, OD
Socket 7	321	37x37 SPGA	VRM	Pentium 75-233+, MMX, OD, AMD K5/K6, Cyrix M1/II
Intel 686 (Pentium II/III) class
Socket	Pins	Layout	Voltage	Supported Processors
Socket 8	387	Dual-pattern SPGA	Auto VRM	Pentium Pro, OD
Slot 1 (SC242)	242	Slot	Auto VRM	Pentium II/III, Celeron SECC
Socket 370	370	37x37 SPGA	Auto VRM	Celeron/Pentium III PPGA/FC-PGA
Pentium 4 class
Socket	Pins	Layout	Voltage	Supported Processors
Socket 423	423	39x39 SPGA	Auto VRM	Pentium 4 FC-PGA
Socket 478	478	26x26 mPGA	Auto VRM	Pentium 4/Celeron FC-PGA2
Socket 775	775	30x33 LGA	Auto VRM	Pentium 4/Celeron LGA775
AMD K7 class
Socket	Pins	Layout	Voltage	Supported Processors
Slot A	242	Slot	Auto VRM	AMD Athlon SECC
Socket A (462)	462	37x37 SPGA	Auto VRM	AMD Athlon/Athlon XP/Duron PGA/FC-PGA
AMD K8 class[2]
Socket	Pins	Layout	Voltage	Supported Processors
Socket 754	743	29x29 mPGA	Auto VRM	AMD Athlon 64,
Socket 939	939	31x31 mPGA	Auto VRM	AMD Athlon 64 v.2,
Socket 940	940	31x31 mPGA	Auto VRM	AMD Athlon 64FX, Opteron
Intel/AMD Server & Workstation class
Socket	Pins	Layout	Voltage	Supported Processors
Slot 2 (SC330)	330	Slot	Auto VRM	Pentium II/III Xeon
Socket 603	603	31x25 mPGA	Auto VRM	Xeon (P4)
PAC418 Socket	611	25x28 mPGA	Auto VRM	Itanium 2
PAC611 Socket 940	940	31x31 mPGA	Auto VRM	AMD Athlon 64FX, Opteron

---

The CPU executes a program, which is a sequence of stored instructions. Each model of processor has an instruction set, which it executes. The CPU executes the program by processing each piece of data as directed by the program and the instruction set. While the CPU is executing one step of the program, the remaining instructions and the data are stored nearby in a special memory called cache. There are two major CPU architectures related to instruction sets:

• Reduced Instruction Set Computer (RISC) \x96 Architectures use a relatively small set of instructions, and RISC chips are designed to execute these instructions very rapidly.
• Complex Instruction Set Computer (CISC) \x96 Architectures use a broad set of instructions, resulting in fewer steps per operation.

Some CPUs incorporate hyperthreading to enhance the performance of the CPU. With hyperthreading, the CPU has multiple pieces of code being executed simultaneously on each pipeline. To an operating system, a single CPU with hyperthreading performs as though there are two CPUs.

The power of a CPU is measured by the speed and the amount of data that it can process. The speed of a CPU is rated in cycles per second. The speed of current CPUs is measured in millions of cycles per second, called megahertz (MHz), or billions of cycles per second, called gigahertz (GHz). The amount of data that a CPU can process at one time depends on the size of the processor data bus. This is also called the CPU bus or the front side bus (FSB). The wider the processor data bus width, the more powerful the processor is. Current processors have a 32-bit or a 64-bit processor data bus.

Overclocking is a technique used to make a processor work at a faster speed than its original specification. Overclocking is not a reliable way to improve computer performance and can result in damage to the CPU. The opposite of overclocking is CPU throttling. CPU throttling is a technique used when the processor runs at less than the rated speed to conserve power or produce less heat. Throttling is commonly used on laptops and other mobile devices.

MMX is a set of multimedia instructions built into Intel processors. MMX enabled microprocessors can handle many common multimedia operations that are normally handled by a separate sound or video card. However, only software specifically written to call MMX instructions can use the MMX instruction set. In Intel CPUs, MMX has been replaced by Streaming Single-instruction-multi-data Extensions (SSE), which is an enhancement to the instruction set. There are many versions of SSE, each of which includes additional instructions.

The latest processor technology has resulted in CPU manufacturers finding ways to incorporate more than one CPU core onto a single chip. Figure 2 lists the most common multiple core processors: (Dual, Triple and Quad Core Processors)

Multiple Core Processors
Dual Intel
Socket	Pins	Layout	Voltage	Supported Processors
Socket T (LGA775)	775	30X33LGA	Auto VRM	Pentium XE, Intel Core 2 Duo, Intel Core 2 Extreme
Socket M	478	Micro FCPGA	Auto VRM	Intel Core Solo, Intel Core Duo, Intel Core 2 Duo (T5x00, T7x00 and T8x00), Intel Celeron M
Dual AMD
Socket	Pins	Layout	Voltage	Supported Processors
Socket S1 (Replaced Socket 754)	638	PGA-ZIF	Auto	Athlon 64 X2, Turion 64 X2, Mobile Sempron, Turion 64 (MK series only)
Socket AM2 (Supports DDR2 but not DDR Memory)	940	PGA-ZIF	Auto	Athlon 64, Athlon 64 X2, Athlon 64 FX, Opteron, Sempron, Phenom
Socket AM2+ (Added Support for DDR3)	940	PGA-ZIF	Auto	Athlon 64, Athlon 64 X2, Opteron, Phenom series: Phenom X2
Socket AM3	941	PGA-ZIF	Auto	Phenom II (excluding 940 and 920), Athlon II
Triple AMD
Socket	Pins	Layout	Voltage	Supported Processors
Socket AM3	941	PGA-ZIF	Auto	Phenom X3
Quad Intel
Socket	Pins	Layout	Voltage	Supported Processors
LGA775	775	30X33LGA	Auto	Intel Core2 Quad
Quad AMD
Socket	Pins	Layout	Voltage	Supported Processors
Socket F	1207	LGA	Auto	Opteron 2xxx, 8xxx series, Athlon 64 FX FX-7x series
Socket AM3	941	PGA-ZIF	Auto	Phenom X4 series

These CPUs are capable of processing multiple instructions concurrently:

• Single Core CPU \x96 One core inside a single CPU chip that handles all of the processing capability. A motherboard manufacturer may provide sockets for more than one single processor, providing the ability to build a powerful, multi-processor computer.
• Dual Core CPU \x96 Two cores inside a single CPU chip in which both cores can process information at the same time.
• Triple Core CPU \x96 Three cores inside a single CPU that is actually a quad-core processor with one of the cores disabled.
• Quad Core CPU \x96 Four cores inside a single CPU in which all cores can process information simultaneously for enhanced software applications.

1.4.3 Identify the names, purposes, and characteristics of cooling systems

Electronic components generate heat. Heat is caused by the flow of current within the components. Computer components perform better when kept cool. If the heat is not removed, the computer may run slower. If too much heat builds up, computer components can be damaged.

Increasing the air flow in the computer case allows more heat to be removed. A case fan, shown in Figure 1 (Case Fan), is installed in the computer case to make the cooling process more efficient.

In addition to case fans, a heat sink draws heat away from the core of the CPU. A fan on top of the heat sink, shown in Figure 2 (CPU Fan), moves the heat away from the CPU.

Other components are also susceptible to heat damage and are sometimes equipped with fans. Video adapter cards also produce a great deal of heat. Fans are dedicated to cool the graphics-processing unit (GPU), as seen in Figure 3 (Graphic Card Cooling System).

Computers with extremely fast CPUs and GPUs may use a water-cooling system. A metal plate is placed over the processor and water is pumped over the top to collect the heat that the CPU creates. The water is pumped to a radiator to be cooled by the air, and then re-circulated.

1.4.4 Identify the names, purposes, and characteristics of ROM and RAM

ROM

Read-only memory (ROM) chips are located on the motherboard. ROM chips contain instructions that can be directly accessed by the CPU. Basic instructions for booting the computer and loading the operating system are stored in ROM. ROM chips retain their contents even when the computer is powered down. The contents cannot be erased or changed by normal means. The different types of ROM are shown in Figure 1 (ROM Types).

ROM Types
ROM	Read-only memory chips. Information is written to a ROM chip when it is manufactured. A ROM chip cannot be erased or re-written and is osolete.
PROM	Programmable read-only memory. Information is written to a PROM chip after it is manufactured. A PROM chip cannot be erased or re-written.
EPROM	Erasable programmable read-only memory. Information is written to an EPROM chip after it is manufactured. An EPROM chip can be erased with exposure to UV light. Special equipment is required.
EEPRROM	Electrically erasable programmable read-only memory. Information is written to an EEPROM chip after it is manufactured. EEPROM chips are also called Flash ROMs. An EEPROM chip can be erased and re-written without having to remove the chip from the computer.

NOTE: ROM is sometimes called firmware. This is misleading because firmware is actually the software that is stored in a ROM chip.

RAM

Random access memory (RAM) is the temporary storage for data and programs that are being accessed by the CPU. RAM is volatile memory, which means that the contents are erased when the computer is powered off. The more RAM in a computer, the more capacity the computer has to hold and process large programs and files, as well as enhance system performance. The different types of RAM are shown in Figure 2: (RAM Types)

RAM Types
DRAM	Dynamic RAM is a memory chip that is used as a main memory. DRAM must be constantly refreshed with pulses of electricity in order to maintain the data stored within the chip
SRAM	Static RAM is a memory chip that is used as cache memory. SRAM is much faster than DRAM does not have to be refreshed as often.
FPM Memory	Fast Page Mode DRAM is memory that supports paging. Paging enables faster access to the data than regular DRAM. Most 486 and Pentium systems from 1995 and earlier use FPM memory.
EDO Memory	Extended Data Out RAM is memory that overlaps consecutive data accesses. This speeds up the access time to retrieve data from memory, because the CPU does not have to wait for one data access cycle to end before another data access cycle beginns.
SDRAM	Synchronous DRAM is DRAM that operates in synchronization with the memory bus. The memory bus is the data path between the CPU and the main memory.
DDR SDRAM	Double Data Rate SDRAM is memory that transfers data twice as fast as SDRAM. DDR SDRAM increases performance by transferring data twice per cycle.
DDR2 SDRAM	Double Data Rate 2 SDRAM is a fasterthan DDR-SDRAM memory. DDR2 SDRAM improves performance over DDR SDRAM by decreasing noise and crosstalk betwen the signal wires.
DDR3 SDRAM	Double Data Rate 3 SDRAM expands memory bandwith by doubling the clock rate of DDR2 SDRAM. DDR3 SDRAM consumes less power and generate less heat than DDR2 SDRAM
RDRAM	RAMBus DRAM is a memory chip that was developed to communicate at very high rates of speed. RDRAM chips are not commonly used.

Memory Modules

Early computers had RAM installed on the motherboard as individual chips. The individual memory chips, called dual inline package (DIP) chips, were difficult to install and often became loose on the motherboard. To solve this problem, designers soldered the memory chips on a special circuit board called a memory module. The different types of memory modules are shown in Figure 3: (Memory Modules)

Memory Modules
DIP	Dual Inline Package is an invidual memory chip. A DIP had dual rows of pins used to attach it to the motherboard.
SIMM	Single Inline Memory Module is a small circuit board that holds several memory chips. SIMMs have 30-pin and 72-pin configurations.
DIMM	Dual Inline Memory Module is a circuit board that holds SDRAM, DDR SDRAM and DDR2 SDRAM chips. There are 168-pin SDRAM DIMMs, 184-pin DDR DIMMs and 240-pin DDR2 DIMMs.
RIMM	RAM Bus Inline Memory Module is a circuit board that holds RDRAM chips. A typical RIMM has a 184-pin configuration.
SODIMM	Small Outline DIMM has a 72-pin configuration for support of 32-bit transfers or a 144-pin configuration for support of 64-bit transfers. This smaller, more condensed version of DIMM provides random access data storage that is ideal for use in laptops, printers and other devices where conserving space is desirable.

NOTE: Memory modules can be single-sided or double-sided. Single-sided memory modules only contain RAM on one side of the module. Double-sided memory modules contain RAM on both sides of the module.

The speed of memory has a direct impact on how much data a processor can process because faster memory improves the performance of the processor. As processor speed increases, memory speed must also increase. For example, single-channel memory is capable of transferring data at 64 bits. Dual-channel memory increases speed by using a second channel of memory, creating a data transfer rate of 128 bits.

Double Data Rate (DDR) technology doubles the maximum bandwidth of SDRAM. DDR2 offers faster performance while using less energy. DDR3 operates at even higher speeds than DDR2; however, none of these DDR technologies are backward- or forward-compatible. See Figure 4 for a chart comparing different memory types and speeds: (Memory Types and Speeds)

Memory Types and Speeds
Memory Type	Industry Name	Peak Transfer Rate	Front Side Bus
PC100 SDRAM	PC-100	800 MB/s	100 Mhz
PC133 SDRAM	PC-133	1060 MB/s	133 MHz
DDR-333	PC-2700	2700 MB/s	166 MHz
DDR-400	PC-3200	3200 MB/s	200 MHz
DDR2-667	PC-5300	5333 MB/s	667 MHz
DDR3-1600	PC-12800	12800 MB/s	1600 MHz

Cache

SRAM is used as cache memory to store the most frequently used data. SRAM provides the processor with faster access to the data than retrieving it from the slower DRAM, or main memory. The three types of cache memory are shown in Figure 5: (Cache Memory)

Cache Memory
L1	L1 cache is internal cache and is integrated into the CPU
L2	L2 cache is external cache and was originally mounted on the motherboard near the CPU. L2 cache is now integrated into the CPU.
L3	L3 cache is used on some high end workstations and server CPUs.

Error Checking

Memory errors occur when the data is not stored correctly in the RAM chips. The computer uses different methods to detect and correct data errors in memory. Figure 6 shows three different methods of memory error checking: (Memory Errors)

Memory Errors
Nonparity:	Nonparity memory does not check for errors in memory.
Parity:	Parity memory contains eight bits for data and one bit for error checking. The error-checking bit is called a parity bit.
ECC:	Error Correction Code memory can detect multiple bit errors in memory and correct single bit errors in memory.

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1.4.5 Identify the names, purposes, and characteristics of adapter cards

Adapter cards increase the functionality of a computer by adding controllers for specific devices or by replacing malfunctioning ports. Figure 1 shows several types of adapter cards. Adapter cards are used to expand and customize the capability of the computer:

• Network Interface Card (NIC) \x96 Connects a computer to a network using a network cable
• Wireless NIC \x96 Connects a computer to a network using radio frequencies
• Sound adapter \x96 Provides audio capability
• Video adapter \x96 Provides graphic capability
• Capture card \x96 Sends a video signal to a computer so that the signal can be recorded to the computer hard drive with Video Capture software
• TV tuner \x96 Provides the ability to watch and record TV signals on a PC by connecting a TV source, such as cable TV, satellite, or an antenna, to the installed tuner card
• Modem adapter \x96 Connects a computer to the Internet using a phone line
• Small Computer System Interface (SCSI) adapter \x96 Connects SCSI devices, such as hard drives or tape drives, to a computer
• Redundant Array of Independent Disks (RAID) adapter \x96 Connects multiple hard drives to a computer to provide redundancy and to improve performance
• Universal Serial Bus (USB) port \x96 Connects a computer to peripheral devices
• Parallel port \x96 Connects a computer to peripheral devices
• Serial port \x96 Connects a computer to peripheral devices

Computers have expansion slots on the motherboard to install adapter cards. The type of adapter card connector must match the expansion slot. A riser card was used in computer systems with the LPX form factor to allow adapter cards to be installed horizontally. The riser card was mainly used in slim-line desktop computers. The different types of expansion slots are shown in Figure 2.

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Expansion Slots

PCI:	Peripheral Component Interconnect is a 32-bit or 64-bit expansion slot. PCI is the standard slot currently used in most computers.
AGP:	Advanced Graphics Port is a 32-bit expansion slot. AGP is designed for video adapters.
PCIe	PCI-Express is a serial bus expansion slot. PCI Express is software campatible with PCI slots. PCI-Express has x1, x4, x8 and x16 slots.
ISA:	Industry Standard Architecture is an 8-bit or 16-bit expansion slot. This is older technology and is seldom used.
EISA:	Extended Industry Standard Architecture is a 32-bit expansion slot. This is older technology and is seldom used.
MCA:	Microchannel Architecture is an IBM-proprietary 32-bit expansion slot. This is older technology and is seldom used.

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1.4.6 Identify the names, purposes, and characteristics of storage drives

A storage drive reads or writes information to magnetic or optical storage media. The drive can be used to store data permanently or to retrieve information from a media disk. Storage drives can be installed inside the computer case, such as a hard drive. For portability, some storage drives can connect to the computer using a USB port, a FireWire port, or an SCSI port. These portable storage drives are sometimes referred to as removable drives and can be used on multiple computers. Here are some common types of storage drives:

• Floppy drive
• Hard drive
• Optical drive
• Flash drive
• Network drive

Floppy Drive

A floppy drive, or floppy disk drive, is a storage device that uses removable 3.5-inch floppy disks. These magnetic floppy disks can store 720 KB or 1.44 MB of data. In a computer, the floppy drive is usually configured as the A: drive. The floppy drive can be used to boot the computer if it contains a bootable floppy disk. A 5.25-inch floppy drive is older technology and is seldom used.

Hard Drive

A hard drive, or hard disk drive, is a magnetic storage device that is installed inside the computer. The hard drive is used as permanent storage for data. In a Windows computer, the hard drive is usually configured as the C: drive and contains the operating system and applications. The hard drive is often configured as the first drive in the boot sequence. The storage capacity of a hard drive is measured in billions of bytes, or gigabytes (GB). The speed of a hard drive is measured in revolutions per minute (RPM). Multiple hard drives can be added to increase storage capacity.

Traditional hard drives are magnetic. Magnetic hard drives have drive motors designed to spin magnetic platters and the drive heads. In contrast, the newer solid state drives (SSDs) do not have moving parts. Because there are no drive motors and moving parts, the SSD uses far less energy than the magnetic hard drive. Non-volatile flash memory chips manage all storage on an SSD, which results in faster access to data, higher reliability, and reduced power usage. SSDs have the same form factor as magnetic hard drives and use ATA or SATA interfaces. SSDs can be installed as a replacement for magnetic drives.

Optical Drive

An optical drive is a storage device that uses lasers to read data on the optical media. There are two types of optical drives:

• Compact disc (CD)
• Digital versatile disc (DVD)

CD and DVD media can be pre-recorded (read-only), recordable (write once), or re-recordable (read and write multiple times). CDs have a data storage capacity of approximately 700 MB. DVDs have a data storage capacity of approximately 8.5 GB on one side of the disc.

An optical drive is a storage device that uses lasers to read data on the optical media. There are three types of optical drives:

• Compact Disc (CD)
• Digital versatile Disc (DVD)
• Blu-ray Disc (BD)

CD, DVD, and BD media can be pre-recorded (read-only), recordable (write once), or re-recordable (read and write multiple times). CDs have a data storage capacity of approximately 700 MB. DVDs have a data storage capacity of approximately 4.3 GB on a single-layer disc, and approximately 8.5 GB on a dual-layer disc. BDs have a storage capacity of 25 GB on a single-layer disc, and 50 GB on a dual-layer disc.

There are several types of optical media:

• CD-ROM \x96 CD read-only memory media that is pre-recorded.
• CD-R \x96 CD recordable media that can be recorded one time.
• CD-RW \x96 CD rewritable media that can be recorded, erased, and re-recorded.
• DVD-ROM \x96 DVD read-only memory media that is pre-recorded.
• DVD-RAM \x96 DVD random access memory media that can be recorded, erased, and re-recorded.
• DVD+/-R \x96 DVD recordable media that can be recorded one time.
• DVD+/-RW \x96 DVD rewritable media that can be recorded, erased, and re-recorded.
• BD-ROM \x96 BD read-only media that is pre-recorded with movies, games, or software.
• BD-R \x96 BD recordable media that can record HD video and PC data storage one time.
• BD-RE \x96 BD rewritable format for HD video recording and PC data storage.

External Flash Drive

An external flash drive, also known as a thumb drive, is a removable storage device that connects to a USB port. An external flash drive uses the same type of non-volatile memory chips as solid state drives and does not require power to maintain the data. These drives can be accessed by the operating system in the same way that other types of drives are accessed.

Types of Drive Interfaces

Hard drives and optical drives are manufactured with different interfaces that are used to connect the drive to the computer. To install a storage drive in a computer, the connection interface on the drive must be the same as the controller on the motherboard. Here are some common drive interfaces:

• IDE \x96 Integrated Drive Electronics, also called Advanced Technology Attachment (ATA) is an early drive controller interface that connects computers and hard disk drives. An IDE interface uses a 40-pin connector.
• EIDE \x96 Enhanced Integrated Drive Electronics, also called ATA-2, is an updated version of the IDE drive controller interface. EIDE supports hard drives larger than 512 MB, enables Direct Memory Access (DMA) for speed, and uses the AT Attachment Packet Interface (ATAPI) to accommodate optical drives and tape drives on the EIDE bus. An EIDE interface uses a 40-pin connector.
• PATA \x96 Parallel ATA refers to the parallel version of the ATA drive controller interface.
• SATA \x96 Serial ATA refers to the serial version of the ATA drive controller interface. A SATA interface uses a 7-pin data connector.
• eSATA \x96 External Serial ATA provides a hot-swappable, external interface for SATA drives. The eSATA interface connects an external SATA drive using a 7-pin connector. The cable can be up to two meters (6.56 ft.) in length.
• SCSI \x96 Small Computer System Interface is a drive controller interface that can connect up to 15 drives. SCSI can connect both internal and external drives. An SCSI interface uses a 50-pin, 68-pin, or 80-pin connector.

RAID provides a way to store data across multiple hard disks for redundancy. To the operating system, RAID appears as one logical disk. See Figure 2 for a comparison of the different RAID levels. The following terms describe how RAID stores data on the various disks:

• Parity \x96 A method used to detect data errors.
• Striping \x96 A method used to write data across multiple drives.
• Mirroring \x96 A method of storing duplicate data to a second drive.

1.4.7 Identify the names, purposes, and characteristics of internal cables

Drives require both a power cable and a data cable. A power supply will have a SATA power connector for SATA drives, a Molex power connector for PATA drives, and a Berg 4-pin connector for floppy drives. The buttons and the LED lights on the front of the case connect to the motherboard with the front panel cables.

Data cables connect drives to the drive controller, which is located on an adapter card or on the motherboard. Here are some common types of data cables:

• Floppy disk drive (FDD) data cable \x96 Data cable has up to two 34-pin drive connectors and one 34-pin connector for the drive controller.
• PATA (IDE/EIDE) 40-conductor data cable \x96 Originally, the IDE interface supported two devices on a single controller. With the introduction of Extended IDE, two controllers capable of supporting two devices each were introduced. The 40-conductor ribbon cable uses 40-pin connectors. The cable has two connectors for the drives and one connector for the controller.
• PATA (EIDE) 80-conductor data cable \x96 As the data rates available over the EIDE interface increased, the chance of data corruption during transmission increased. An 80-conductor cable was introduced for devices transmitting at 33.3 MB/s and over, allowing for a more reliable balanced data transmission. The 80-conductor cable uses 40-pin connectors.
• SATA data cable \x96 This cable has seven conductors, one keyed connector for the drive, and one keyed connector the drive controller.
• eSATA data cable \x96 The eSATA external disk connects to the eSATA interface using a 7-pin data cable. This cable does not supply any power to the eSATA external disk. A separate power cable provides power to the disk.
• SCSI data cable \x96 There are three types of SCSI data cables. A narrow SCSI data cable has 50 conductors, up to seven 50-pin connectors for drives, and one 50-pin connector for the drive controller, also called the host adapter. A wide SCSI data cable has 68 conductors, up to 15 68-pin connectors for drives, and one 68-pin connector for the host adapter. An Alt-4 SCSI data cable has 80 conductors, up to 15 80-pin connectors for drives, and one 80-pin connector for the host adapter.

NOTE: A colored stripe on a cable identifies Pin 1 on the cable. When installing a data cable, always ensure that Pin 1 on the cable aligns with Pin 1 on the drive or drive controller. Some cables may be keyed and therefore they can only be connected one way to the drive and drive controller.

Worksheet

Computer Components Research computer components

1.5 Identify the names, purposes, and characteristics of ports and cables

Input/output (I/O) ports on a computer connect peripheral devices, such as printers, scanners, and portable drives. The following ports and cables are commonly used:

• Serial
• USB
• FireWire
• Parallel
• SCSI
• Network
• PS/2
• Audio
• Video

Serial Ports and Cables

A serial port can be either a DB-9, as shown in Figure 1, or a DB-25 male connector. Serial ports transmit one bit of data at a time. To connect a serial device, such as a modem or printer, a serial cable must be used. A serial cable has a maximum length of 50 feet (15.2 m).

Modem Ports and Cables

In addition to the serial cable used to connect an external modem to a computer, a telephone cable is used to connect a modem to a telephone outlet. This cable uses an RJ-11 connector, as shown in Figure 2. A traditional setup of an external modem using a serial cable and a telephone cable is shown in Figure 3.

USB Ports and Cables

The Universal Serial Bus (USB) is a standard interface that connects peripheral devices to a computer. It was originally designed to replace serial and parallel connections. USB devices are hot-swappable, which means that users can connect and disconnect the devices while the computer is powered on. USB connections can be found on computers, cameras, printers, scanners, storage devices, and many other electronic devices. A USB hub is used to connect multiple USB devices. A single USB port in a computer can support up to 127 separate devices with the use of multiple USB hubs. Some devices can also be powered through the USB port, eliminating the need for an external power source. Figure 4 shows USB cables with connectors.

USB 1.1 allowed transmission rates of up to 12 Mbps in full-speed mode and 1.5 Mbps in low-speed mode. USB 2.0 allows transmission speeds up to 480 Mbps. USB devices can only transfer data up to the maximum speed allowed by the specific port.

FireWire Ports and Cables

FireWire is a high-speed, hot-swappable interface that connects peripheral devices to a computer. A single FireWire port in a computer can support up to 63 devices. Some devices can also be powered through the FireWire port, eliminating the need for an external power source. FireWire uses the IEEE 1394 standard and is also known as i.Link.

The IEEE 1394a standard supports data rates up to 400 Mbps and cable lengths up to 15 feet (4.5 m). This standard uses a 6-pin connector or a 4-pin connector. The IEEE 1394b standard allows for a greater range of connections, including CAT5 UTP and optical fiber. Depending on the media used, data rates are supported up to 3.2 Gbps over a 100m distance. Figure 5 shows FireWire cables with connectors.

Parallel Ports and Cables

A parallel port on a computer is a standard Type A DB-25 female connector. The parallel connector on a printer is a standard Type B 36-pin Centronics connector. Some newer printers may use a Type C high-density 36-pin connector. Parallel ports can transmit 8 bits of data at one time and use the IEEE 1284 standard. To connect a parallel device, such as a printer, a parallel cable must be used. A parallel cable, as shown in Figure 6, has a maximum length of 15 feet (4.5 m).

SCSI Ports and Cables

A SCSI port can transmit parallel data at rates in excess of 320 MBps and can support up to 15 devices. If a single SCSI device is connected to an SCSI port, the cable can be up to 80 feet (24.4 m) in length. If multiple SCSI devices are connected to an SCSI port, the cable can be up to 40 (12.2 m) feet in length. An SCSI port on a computer can be one of three different types, as shown in Figure 7:

• 80-pin connector
• 50-pin connector
• 68-pin connector

NOTE: SCSI devices must be terminated at the endpoints of the SCSI chain. Check the device manual for termination procedures.

CAUTION: Some SCSI connectors resemble parallel connectors. Be careful not to connect the cable to the wrong port. The voltage used in the SCSI format may damage the parallel interface. SCSI connectors should be clearly labeled.

Network Ports and Cables

A network port, also known as an RJ-45 port, connects a computer to a network. The connection speed depends on the type of network port. Standard Ethernet can transmit up to 10 Mbps, Fast Ethernet can transmit up to 100 Mbps, and Gigabit Ethernet can transmit up to 1000 Mbps. The maximum length of network cable is 328 feet (100 m). A network connector is shown in Figure 8.

PS/2 Ports

A PS/2 port connects a keyboard or a mouse to a computer. The PS/2 port is a 6-pin mini-DIN female connector. The connectors for the keyboard and mouse are often colored differently, as shown in Figure 9. If the ports are not color-coded, look for a small figure of a mouse or keyboard next to each port.

Audio Ports

An audio port connects audio devices to the computer. Some of the following audio ports are commonly used, as shown in Figure 10:

• Line In \x96 Connects to an external source, such as a stereo system
• Microphone \x96 Connects to a microphone
• Line Out \x96 Connects to speakers or headphones
• Sony/Philips Digital Interface Format (S/PDIF) \x96 Connects to fiber optic cable to support digital audio
• TosLink \x96 Connects to coaxial cable to support digital audio
• Gameport/MIDI \x96 Connects to a joystick or MIDI-interfaced device

Video Ports and Connectors

A video port connects a monitor cable to a computer. Figure 11 shows three common video ports. There are several video port and connector types:

• Video Graphics Array (VGA) \x96 VGA has a 3-row, 15-pin female connector and provides analog output to a monitor.
• Digital Visual Interface (DVI) \x96 DVI has a 24-pin female connector or a 29-pin female connector and provides an uncompressed digital output to a monitor. DVI-I provides both analog and digital signals. DVI-D provides digital signals only.
• High-Definition Multimedia Interface (HDMi) \x96 HDMi has a 19-pin connector and provides digital video and digital audio signals.
• S-Video \x96 S-Video has a 4-pin connector and provides analog video signals.
• Component/RGB \x96 RGB has three shielded cables (red, green, blue) with RCA jacks and provides analog video signals.

1.6 Identify the names, purposes, and characteristics of input devices

An input device is used to enter data or instructions into a computer. Here are some examples of input devices:

* Mouse and keyboard * Digital camera and digital video camera * Biometric authentication device * Touch screen * Scanner

The mouse and keyboard are the two most commonly used input devices. The mouse is used to navigate the graphical user interface (GUI). The keyboard is used to enter text commands that control the computer.

A keyboard, video, mouse (KVM) switch is a hardware device that can be used to control more than one computer using a single keyboard, monitor, and mouse. KVM switches provide cost-efficient access to multiple servers using a single keyboard, monitor, and mouse for businesses. Home users can save space using a KVM switch to connect multiple computers to one keyboard, monitor, and mouse. See Figure 1.

Newer KVM switches have added the capability to share USB devices and speakers with multiple computers. Typically, by pressing a button on the KVM switch, the user can change the control from one connected computer to another connected computer. Some models of the switch transfer control from one computer to another computer using a specific key sequence on a keyboard, such as CNTL > CNTL > A > ENTER to control the first computer connected to the switch, then CNTL > CNTL > B > ENTER to transfer control to the next computer.

Digital cameras and digital video cameras, shown in Figure 2, create images that can be stored on magnetic media. The image is stored as a file that can be displayed, printed, or altered.

Biometric identification makes use of features that are unique to an individual user, such as fingerprints, voice recognition, or a retinal scan. When combined with ordinary usernames, biometrics guarantees that the authorized person is accessing the data. Figure 3 shows a laptop that has a built-in fingerprint scanner. By measuring the physical characteristics of the fingerprint of the user, the user is granted access if the fingerprint characteristics match the database and the correct login information is supplied.

A touch screen has a pressure-sensitive transparent panel. The computer receives instructions specific to the place on the screen that the user touches.

A scanner digitizes an image or document. The digitization of the image is stored as a file that can be displayed, printed, or altered. A bar code reader is a type of scanner that reads universal product code (UPC) bar codes. It is widely used for pricing and inventory information.

1.7 Identify the names, purposes, and characteristics of output devices

An output device is used to present information to the user from a computer. Here are some examples of output devices:

• Monitors and projectors
• Printers, scanners, and fax machines
• Speakers and headphones

Monitors and Projectors

Monitors and projectors are primary output devices for a computer. There are different types of monitors, as shown in Figure 1. The most important difference between these monitor types is the technology used to create an image:

• CRT \x96 Cathode-ray tube monitor is the most common monitor type. There are three electron beams. Each focused to hit colored phosphor on the screen which will glow either red, blue or green. Areas not struck by the electron beam do not glow. The combination of glowing and non-glowing areas is what creates the image on the screen. Most televisions also use this technology.
• LCD \x96 Liquid crystal display is commonly used in laptops and some projectors. It consists of two polarizing filters with a liquid crystal solution between them. An electronic current aligns the crystals so that light can either pass through or not pass through. The effect of light passing through in certain areas and not in others is what creates the image. LCD comes in two forms, active matrix and passive matrix. Active matrix is sometimes called thin film transistor (TFT). TFT allows each pixel to be controlled, which creates very sharp color images. Passive matrix is less expensive than active matrix but does not provide the same level of image control.
• DLP \x96 Digital light processing is another technology used in projectors. DLP projectors use a spinning color wheel with a microprocessor-controlled array of mirrors called a digital micromirror device (DMD). Each mirror corresponds to a specific pixel. Each mirror reflects light toward or away from the projector optics. This creates a monochromatic image of up to 1024 shades of gray in between white and black. The color wheel then adds the color data to complete the projected, color image.

Monitor resolution refers to the level of image detail that can be reproduced. Figure 2 is a chart of common monitor resolutions.

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Display Resolutions

Display Standard	Linear Pixels (HXV)	Aspect Ratio
CGA	320x200	16:10
EGA	640x350	11:6
VGA	640x480	4:3
WVGA	854x480	16:9
SVGA	800x600	4:3
XGA	1024x768	4:3
WXGA	1280x800	16:10
SXGA	1280x1024	5:4
SXGA+	1400x1050	4:3
WSXGA	1600x1024	25:16
UXGA	1600x1200	4:3
HDTV	1920x1080	16:9
WUXGA	1920x1200	16:10
QXGA	2048x1536	4:3
QSXGA	2560x2048	5:4
WQUXGA	3840x2400	16:10

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Higher resolution settings produce better image quality. There are several factors involved in monitor resolution:

• Pixel \x96 The term pixel is an abbreviation for picture element. Pixels are the tiny dots that comprise a screen. Each pixel consists of red, green, and blue.
• Dot pitch \x96 Dot pitch is the distance between pixels on the screen. A lower dot pitch number produces a better image.
• Contrast ratio \x96 The contrast ratio is a measurement of the difference in intensity of light between the brightest point (white) and the darkest point (black). A 10,000:1 contrast ratio shows dimmer whites and lighter blacks than a monitor with a contrast ratio of 1,000,000:1.
• Refresh rate \x96 The refresh rate is how often per second the image is rebuilt. A higher refresh rate produces a better image and reduces the level of flicker.
• Interlace/Non-Interlace \x96 Interlaced monitors create the image by scanning the screen two times. The first scan covers the odd lines, top to bottom, and the second scan covers the even lines. Non-interlaced monitors create the image by scanning the screen, one line at a time from top to bottom. Most CRT monitors today are non-interlaced.
• Horizontal Vertical Colors (HVC) \x96 The number of pixels in a line is the horizontal resolution. The number of lines in a screen is the vertical resolution. The number of colors that can be reproduced is the color resolution.
• Aspect ratio \x96 Aspect ratio is the horizontal to vertical measurement of the viewing area of a monitor. For example, a 4:3 aspect ratio would apply to a viewing area that is 16 inches wide by 12 inches high. A 4:3 aspect radio would also apply to a viewing area that is 24 inches wide by 18 inches high. A viewing area that is 22 inches wide by 12 inches high has an aspect ratio of 11:6.
• Native resolution \x96 Native resolution is the number of pixels that a monitor has. A monitor with a resolution of 1280x1024 has 1280 horizontal pixels and 1024 vertical pixels. Native mode is when the image sent to the monitor matches the native resolution of the monitor.

Monitors have controls for adjusting the quality of the image. Here are some common monitor settings:

• Brightness \x96 Intensity of the image
• Contrast \x96 Ratio of light to dark
• Position \x96 Vertical and horizontal location of image on the screen
• Reset \x96 Returns the monitor settings to factory settings

Adding additional monitors increases the number of windows that are visible on the desktop. Many computers have built-in support for multiple monitors. See Figure 3 for more information about configuring multiple monitors.

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Connecting Multiple Monitors to a single Computer

Hardware needed

• Two video ports are needed. Install a video adapter for an additional port or purchase an adapter with two video ports. Disable the motherboard video port if necessary. Note that some motherboards automaticly disable the integrated video portif a video adaper is installed.
• Additional monitor(s)

Software Configuration

In Windows XP, enable Dualview:

1. Right click the desktop and then choose Properties
2. Click Display Properties - Setting tab. (The Settings window should show two monitor icons.)
3. From the Display list, click the external monitor. (If multiple monitors are not displayed on the screen, the monitor may not support Dualview.)
4. Click the Extend my Windows desktop onto this monitor check box.
5. Click Identify. Windows XP will display large numbers to identify the two monitors. Drag and drop the monitor icons to match the physical arrangement of the monitors.
6. Click OK

Advantages

• Extending the Windows desktop across two monitors is an inexpensive way to enhance a computer.
• Dualview can also be used to add a second monitor to laptops.
• Using multiple monitors increases productivity. For example a user can use one screen to video conference while taking notes in an application displayed on the other monitor.

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All-in-One Printer

Printers are output devices that create hard copies of computer files. Some printers specialize in particular applications, such as printing color photographs. Other all-in-one type printers, like the one shown in Figure 4, are designed to provide multiple services such as printing, scanning, faxing, and copying.

Speakers and Headphones

Speakers and headphones are output devices for audio signals. Most computers have audio support either integrated into the motherboard or on an adapter card. Audio support includes ports that allow input and output of audio signals. The audio card has an amplifier to power headphones and external speakers, which are shown in Figure 5.

1.8 Explain system resources and their purposes

System resources are used for communication purposes between the CPU and other components in a computer. There are three common system resources:

• Interrupt Requests (IRQ)
• Input/Output (I/O) Port Addresses
• Direct Memory Access (DMA)

Interrupt Requests

IRQs are used by computer components to request information from the CPU. The IRQ travels along a wire on the motherboard to the CPU. When the CPU receives an interrupt request, the CPU determines how to fulfill this request. The priority of the request is determined by the IRQ number assigned to that computer component. Older computers only had eight IRQs to assign to devices. Newer computers have 16 IRQs, which are numbered 0 to 15, as shown in Figure 1. As a general rule, each component in the computer must be assigned a unique IRQ. IRQ conflicts can cause components to stop functioning and even cause the computer to crash.

Today, most IRQ numbers are assigned automatically with plug and play (PnP) operating systems and the implementation of PCI slots, USB ports, and FireWire ports. With the numerous components that can be installed in a computer, it is difficult to assign a unique IRQ to every component. PCI devices can now share IRQs without conflict.

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Interrupt Requests (IRQs)

IRQ 0	System Timer
IRQ 1	Keyboard Controller
IRQ 2	2nd IRQ Controller Cascade
IRQ 3	Serial 2 (COM2:)
IRQ 4	Serial 1 (COM1:)
IRQ 5	Sound/Parallel 2 (LPT2:)
IRQ 6	Floppy Drive Controller
IRQ 7	Parallel 1 (LPT1:)
IRQ 8	Real-Time Clock
IRQ 9	Avail. (as IRQ2 or IRQ9)
IRQ 10	Available
IRQ 11	Available
IRQ 12	Mouse Port/Available
IRQ 13	Math Coprocessor
IRQ 14	Primary IDE
IRQ 15	Secondary IDE

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Input/Output (I/O) Port Addresses

Input/output (I/O) port addresses are used to communicate between devices and software. The I/O port address is used to send and receive data for a component. As with IRQs, each component will have a unique I/O port assigned. There are 65,535 I/O ports in a computer, and they are referenced by a hexadecimal address in the range of 0000h to FFFFh. Figure 2 shows a chart of common I/O ports.

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I/O Port Addresses

Device	I/O Port Address
COM 1	3F8
COM 2	2F8
COM 3	3E8
COM 4	2E8
LPT 1	378
LPT 1	278

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Direct Memory Access

DMA channels are used by high-speed devices to communicate directly with main memory. These channels allow the device to bypass interaction with the CPU and directly store and retrieve information from memory. Only certain devices can be assigned a DMA channel, such as SCSI host adapters and sound cards. Older computers only had four DMA channels to assign to components. Newer computers have eight DMA channels that are numbered 0 to 7, as shown in Figure 3.

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DMA Channels

DMA Channel	Recommended Use
0	Sound
1	Sound
2	Floppy Drive Controller
3	LPT1: in ECP Mode
4	Cascade for DMA 0-3
5	Sound
6	Available
7	Available

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1.9 Summary

This chapter introduced the IT industry, options for training and employment, and some of the industry-standard certifications. This chapter also covered the components that comprise a personal computer system. Much of the content in this chapter will help you throughout this course:

• Information Technology encompasses the use of computers, network hardware, and software to process, store, transmit, and retrieve information.
• A personal computer system consists of hardware components and software applications.
• The computer case and power supply must be chosen carefully to support the hardware inside the case and allow for the addition of components.
• The internal components of a computer are selected for specific features and functions. All internal components must be compatible with the motherboard.
• You should use the correct type of ports and cables when connecting devices.
• Typical input devices include the keyboard, mouse, touch screen, and digital cameras.
• Typical output devices include monitors, printers, and speakers.
• System resources must be assigned to computer components. System resources include IRQs, I/O port addresses, and DMAs.

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-- KlausKellermann - 06 Sep 2010