Computer Service and Repair Chapter 1 1

Introduction to a Typical PC

Computer Service & Repair Chapter 1

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Key Terms

• Computer: An assembly of electronic modules that interact with programs to create, modify, transmit, store, and display data.

• Data: Information (text, graphics and sound)• Digital vs. Analog–Digital: Data represented by a series of simple

on/off switches.–Analog: Data represented by varying voltage

levels (think dimmer switch)

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Key TermsComputer Data Codes:

• Binary Number System:• Number system consisting of 1’s and 0’s• Perfect for on/off digital systems

• Hexadecimal Number Code:• Number system consisting of 16 characters• Matches hardware systems (6,16,32,or 64 wide)

• ASCII:• American Standard Code for Information Interchange• First attempt to standardize computer character codes

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Base 10 Binary (base 2) Hexadecimal (base 16)

ASCII(128 CHARACTERS)

0 0 0 NULL

1 1 1 SOH

2 10 2 STX

3 11 3 ETX

4 100 4 EOT

5 101 5 ACK

6 110 6 BEL

7 111 7 BS

8 1000 8 HT

9 1001 9 LF

10 1010 A VT

11 1011 B FF

12 1100 C CR

13 1101 D SO

14 1110 E SI

15 1111 F DLE

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Key Terms

• Bit (b): Short for “Binary Digit” 1 or 0• Bytes (B): eight bits• Words: the total amount of bytes a

computer can process at one time–Varies from computer to computer–1 to 8 bytes

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Key Terms

Serial vs. Parallel Data Transfer• Serial transfer:– Data is sent through a port one BIT at a time– Used due to limited capacity of media (phone line)– Slow

• Parallel transfer:– More than one Bit is sent side by side through a port – Used on internal bus (RAM to CPU)– Fast

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Key Terms

Computer Numerical Values:• Storage is expressed in Bytes• Speed is expressed in Bits• Uses Metric Prefix names

• Used base 2 not base 10• i.e. Kilo is 210 not 103

• Nano = .000 000 001 (Billionth)• Milli = .000 001 (millionth)• Kilo = 1,000 (thousand)• Mega = 1,000,000 (million)• Giga = 1,000,000,000 (billion)

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Outside the Computer Case• Workstation consists of a computer, input device

and output device• Computer is a case that contains: motherboard,

CPU, memory, hard drive & etc.• Input device typically keyboard and mouse– But there are others

• Output device typically monitor, printer, & speakers– But there are others

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Outside the Computer Case

• Peripherals are optional pieces of equipment used to display or input data– Monitor– Printer– Keyboard– Scanner– Barcode reader – Etc.

• Cases contain and protect electronic parts– Tower– Desk top– Mini tower– Laptop– Notebook

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Outside the Computer CaseExterior Connections• Mini DIN– Connections used for keyboard and mouse– May or may not be interchangeable

• FireWire (IEEE-1394)– More often seen on Apple computers– Hot swap can change device while PC is running

• USB Universal Service Bus– Eliminates need to open case to connect devices to

computers main bus– Hot swap

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Outside the Computer Case• Device Bay: drive bay

designed to hot swap drives. Bay is prewired with FireWire or USB

• RJ– RJ 11 (Modem)

Phone connection– RJ 45 (Ethernet)

NIC connection

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Outside the Computer Case• DB “D” Shaped connection– 9, 15, or 25 pins– Sound Card DB (game port)– HD15 Monitor connection– Replaced by USB

• VGA– HD 15 DB Port– Analog Port

• DVI & HDMI (display ports)– Digital ports

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Outside the Computer Case

• SATA– Data connection to

external SATA device– Does NOT supply power

to external device

• Power eSATA– Same as SATA but

supplies power to external device

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Lab 1

Identify Ports

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Inside the Case• CPU: Central Processing Unit– Brain of the computer– Silicon chip– Millions of Transistors (on/off switches)– Controls actions of computer components– CPU is controlled by Software– Intel, Celeron, and AMD

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Inside the Case• Power Supply– Converts 120 AC

power from wall outlet to DC

– Usually 3.3, 5, or 12 volts DC

– Lower DC voltage needed to avoid damage to Components

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Inside the Case• Hard Drive: Internal

Drive– Consists of several disks

sealed in a sealed box– Data and programs are

stored as magnetic patterns

– Connected to power supply and motherboard

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Inside the Case• Motherboard– Rectangular printed

circuit board– Distributes power

and digital signals (data and instruction)

– This electrical system of pathways is called the computer bus

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Inside the Case• RAM (random access

memory)– Stores programs loaded

from hard drive– Volatile memory system

(data lost when power is turned off)

– Increasing RAM most common upgrade

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Inside the Case• Firmware:– Hardware specific

software required to boot the computer and support communication operating system and hardware devices

– Translates commands into actions

– Found on mother board and in many devices

– Includes SETUP utility

- Once permanently burned onto “ROM chips”

- Now on EEPROM (electronically erasable programmable ROM)

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Inside the Case• Driver: a small software program written

specifically for hardware• CMOS: (complementary metal oxide

semiconductor) it is where the setup utility stores date, time, and hardware information.

• BIOS small 64kB firmware – There is no standard BIOS– May cause compatibility problems

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Inside the Case• Battery: – Supplies voltage to

CMOS– Without battery system

would lose date, time and information about hardware when power is turned off

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Inside the CaseExpansion Slots: Expansion cards:

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Inside the Case• Cooling Fans– Excessive heart damages electronic components

• Cables: – SATA Serial ATA

– PATA Parallel ATA

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Lab 2

Identify Components

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How the Major Parts Work Together

1. Power turned on. Power supply converts AC to DC and fan turns on

2. Firmware is activated and performs a POST (power on self test) checks components to ensure they are working properly.

3. After Firmware checks system Operating system is loaded and takes over.

4. The CPU now waits for activity generated by mouse, keyboard, or other input device. The CPU is checking for commands thousands of time per second

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How the Major Parts Work Together

5. Once user selects a program icon (lets say WORD). The software represented by icon is activated and shares control of the CPU.

6. Some typing is done.7. When WORD saves the operating system takes

over with the firmware. 8. Operating system interprets the command and

translates it to a set of instructions that the firmware can interpret.

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How the Major Parts Work Together

9. The firmware translates the instructions to the storage media (usually the hard drive)

10. The hard drive activates its motor and actuator arm then writes data to next available sector.

11. Control is then returned to WORD (unless an error occurs (i.e. disk full or un readable)

12. rinse and repeat…

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Dangers to / from Computers

• ESD: Electrostatic Discharge– Static Discharge– ESD can Destroy miniature circuits inside a

computer chip – Anti-static Wrist Strap

Prevents ESD– Or just touch metal in

the case before touching anything inside the case

– Shipped in Anti-static bags

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Dangers to / from Computers

• EMI: Electromagnetic Interference– Damage to components caused by magnetic fields– Most common source of magnetic field magnetic

tools (screwdrivers)– Less reliance on magnetic media and shielding

have minimized potential damage.– But why risk it avoid magnetic tools .

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Dangers to / from Computers

• RFI: Radio Frequency Interference– Radio Waves– Normally not a problem because radio waves tend

to be very weak.– Wireless networks may act erratically or fail• Microwave ovens• Baby monitors• Cell phones• Cordless phones

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Dangers to / from Computers

• Physical Safety– Cables (tripping hazard)• Floor runner/tape • Avoid rugs (fire hazard)

– Loose Clothing– Weight • 50 LBS max.• OHSA (Occupation Health and Safety

Administration

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Dangers to / from Computers• Fire Safety:– Class A Ordinary materials (paper and wood)– Class B Flammable Liquids (gasoline oil)– Class C Energized Electrical Equipment– Class D Combustible Metals (potassium)– Class K Kitchen Fires (cooking grease)

• Chemical Safety:– CRT Monitor (lead)– Some TONER (check MSDS)

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End of Chapter 1

Any Questions?Ready for a test?