CSCI-100 Introduction to Computing Hardware Part I

© Prentice-Hall, Inc Hardware: The Basic Components of a Computer  Four primary components: Input Devices Input Devices Processor Processor Output devices Output devices Storage Storage

© Prentice-Hall, Inc The Processor  Also called central processing unit (CPU)  Center of activity in the computer Consists of electronic circuits Consists of electronic circuits Interprets and executes program instructionsInterprets and executes program instructions Communicates with input, output, and storage devicesCommunicates with input, output, and storage devices  Actually transforms data into information

© Prentice-Hall, Inc Storage: Primary Storage  Used to temporarily hold data After it is retrieved from input device and before it is processed After it is retrieved from input device and before it is processed After it is processed and before it is released to output device After it is processed and before it is released to output device  Temporary (volatile) storage Data in memory lost if power is lost or program closed Data in memory lost if power is lost or program closed

Primary Memory  Memory RAM (Random Access Memory)  ROM (Read Only Memory)

© Prentice-Hall, Inc Storage: Secondary Storage  Provides long-term storage Separate from memory Separate from memory  Common media Magnetic disks Magnetic disks Optical disks Optical disks Magnetic tape Magnetic tape

© Prentice-Hall, Inc Magnetic Disks  The most common storage media Diskette: 3.5” flexible diskette in plastic case Diskette: 3.5” flexible diskette in plastic case Hard Disk: more storage capacity and faster access than diskette Hard Disk: more storage capacity and faster access than diskette

© Prentice-Hall, Inc Optical Disks  Use a laser beam to read large volumes of data inexpensively CD-ROMs CD-ROMs DVD-ROMs DVD-ROMs

© Prentice-Hall, Inc Magnetic Tape  Stores large amounts of data inexpensively  Often used for system backup

© Prentice-Hall, Inc OFF ON 01 OR = 1 bit OR = 1 Byte OFF 00 How Computers Represent Data ü Bit (Binary digit) – On or off state of electric current; considered the basic unit of information; represented by 1s and 0s (binary numbers) ü Byte – Eight bits grouped together to represent a character (an alphabetical letter, a number, or a punctuation symbol); How many possible combinations? ON

© Prentice-Hall, Inc Bit Basics  A bit (binary digit) Is the smallest unit of information Is the smallest unit of information Can have two values: or Can have two values: 1 or 0 Can represent numbers, codes, or instructions Can represent numbers, codes, or instructions On

© Prentice-Hall, Inc Bits as Codes   ASCII – American Standard Code for Information Interchange   Most widely used code, represents each character as a unique 8-bit code

© Prentice-Hall, Inc Bits as Instructions  The computer stores instructions as collections of bits. For instance, might instruct the computer to add two numbers  The computer stores instructions as collections of bits. For instance, might instruct the computer to add two numbers  Other bit instructions might include where to find numbers stored in memory or where to store them

© Prentice-Hall, Inc 8 bits = 1 Byte 1024 Bytes = 1 Kilobyte (KB) 1,048,576 Bytes = 1 Megabyte (MB) 1,043,741,824 Bytes = 1 Gigabyte (GB) 1,099,511,627,776 Bytes = 1 Terabyte (TB) Bytes ü Kilobyte, megabyte, gigabyte, and terabyte are terms that describe large units of data used in measuring data storage Example: 20 GB hard drive Example: 20 GB hard drive

© Prentice-Hall, Inc Inside the System Unit ü Motherboard (mainboard) – Large printed circuit board with thousands of electrical circuits ü Power supply – Transforms alternating current (AC) from wall outlets to direct current (DC) needed by the computer ü Cooling fan – Keeps the system unit cool ü Internal Speaker – Used for beeps when errors are encountered ü Drive bays – Housing for the computer’s hard drive, floppy drive, and CD-ROM / DVD- ROM drives

© Prentice-Hall, Inc The Motherboard  The motherboard provides the centralized connection point for the computer’s components Most components are integrated circuits (chips) Most components are integrated circuits (chips) Chips carry electrical current and contain electronic switches or transistorsChips carry electrical current and contain electronic switches or transistors

© Prentice-Hall, Inc The Central Processing Unit: The Microprocessor CPU CPU socket  Central processing unit (CPU) – A microprocessor that interprets and carries out instructions given by software. It controls the computer’s components

© Prentice-Hall, Inc Components of the CPU ü Control unit – Coordinates and controls all parts of the computer system ü Arithmetic-logic unit – Performs arithmetic or logical operations ü Registers – Temporarily store the most frequently used instructions and data

© Prentice-Hall, Inc The Control Unit ü The control unit manages four basic operations (fetch, decode, execute, and write-back) The four-step process is known as the machine cycle or processing cycle The processing cycle consists of two phases: Instruction Cycle Fetch – Gets the next program instruction from the computer’s memory Decode – Figures out what the program is telling the computer to do Execution Cycle Execute – Performs the requested action Write-back (Store) – Writes (stores) the results to a register or to memory

© Prentice-Hall, Inc The Arithmetic-Logic Unit  (ALU) performs basic arithmetic and logic operations  The arithmetic-logic unit (ALU) performs basic arithmetic and logic operations Adds, subtracts, multiplies, and divides Adds, subtracts, multiplies, and divides Compares alphanumeric data Compares alphanumeric data

Arithmetic Operation  Example: Addition     © Prentice-Hall, Inc

Logic Operation ABA and BA or Bnot A © Prentice-Hall, Inc

The Local Bus  The Bus is the circuitry on the motherboard (the main board that holds the microprocessor, memory, and adapter cards) that provides a path for which data travels from one component to another. the circuitry on the motherboard (the main board that holds the microprocessor, memory, and adapter cards) that provides a path for which data travels from one component to another.

The Local Bus  Today’s PCs have multiple local buses each Bus is 32bits wide and travels as fast as the microprocessor. each Bus is 32bits wide and travels as fast as the microprocessor. each Bus is connected to a specific device and does not have to share it with other components. each Bus is connected to a specific device and does not have to share it with other components. PCI - A bus designed by Intel for the Pentium or Pentium Pro. PCI - A bus designed by Intel for the Pentium or Pentium Pro.