chapter 2: computer hardware€¢ 1 peta byte (pb) = 1024 tb = 250 bytes • 1 exa byte (eb) = 1024...
TRANSCRIPT
Chapter 2:
Computer Hardware
2.1 Central Processing Unit
2.2 Primary memory devices
2.3 Secondary memory device
2.4 Input Devices
2.5 Output Devices
Session 2014-15 B.Ed Elementary
Central Processing Unit• The part of the computer performs the bulk of data
processing operations is called the central processing unit
• The CPU is made up of three major parts:– Register set
– ALU
– Control unit
The central processing unit (CPU) of a computer is the main unit that dictates the rest of the computer organization
• 1. Register set: Stores intermediate data during the execution of instructions;
• 2. Arithmetic logic unit (ALU): Performs the required micro-operations for executing the instructions;
• 3. Control unit: supervises the transfer of information among the registers and instructs the ALU as to which operation to perform by generating control signals.
ControlUnit
Registers
ArithmeticLogic Unit
• Central Processing Unit = “brain”
• Executes programs by:
– Fetching and decoding the next instruction from memory
– Execute it
• Consists of:
– Control Unit
– Arithmetic Logic Unit (ALU)
– Registers (high-speed memory)
• Program Counter (PC)
• Instruction Register (IR)
Disk PrinterMain
Memory
ControlUnit
Registers
ArithmeticLogic Unit
Bus
I/O Devices
• 1 Bit- Binary digit ‘0’ or ‘1’.
• 1 Nibble = 4 Bits
• 1 Byte = 8 Bits
• 1 Kilo Byte (KB) = 1024 Bytes = 210 Bytes
• 1 Mega Byte (MB) = 1024 KB = 220 Bytes
• 1 Giga Byte (GB) = 1024 MB = 230 Bytes
• 1 Tera Byte (TB) = 1024 GB = 240 Bytes
• 1 Peta Byte (PB) = 1024 TB = 250 Bytes
• 1 Exa Byte (EB) = 1024 PB = 260 Bytes
• Also known as the main memory.
• It is mostly temporary or working storage.
• Data access speed is faster as compared to
Secondary memory devices.
• Four principal types of memory chips are:
– RAM, ROM, CMOS, and Flash
• Holds temporarily (hence volatile):
– Software instructions.
– Data before and after it is processed by the
CPU.
• Volatile means the contents are lost when
the power goes off or is turned off.
• DRAM (Dynamic RAM) must be constantly
refreshed by the CPU.
• SDRAM (Synchronous DRAM)
synchronized by the system clock.
• SRAM (Static RAM) no refreshing.
• DDR-SDRAM (Double-data rate SDRAM)
• ROM chips contain fixed start-up
instructions, mostly loaded by the
manufacturer.
• It holds instructions that run the computer
when it is first turned on (BIOS).
• It is permanent memory (Non-volatile)
• PROM (Programable ROM)
• EPROM (Eraseable PROM)
– UVEPROM
– EEPROM also known as flash memory
• Complementary Metal Oxide
Semiconductor are powered by a battery
and thus they do not lose their contents
when the power is turned off.
• Can be reprogrammed.
• Does not require a battery.
• Can be erased and reprogrammed more than
once.
• Used in PCs, pagers, cell phones, MP3 players
etc.
• Flash memory is also used in newer PC’s for
BIOS instructions; they can be updated
electronically.
• Pronounced as ‘Cash’.
• Cache temporarily stores instructions and data
that the processor is likely to use frequently. Thus,
cache speeds up processing.
• SRAM chips are commonly used as cache.
• Three kinds of Cache:
– L1 part of the processor. Less capacity, operates faster.
– L2 not part of the processor, high capacity.
– L3 on the mother board- on very high-end computers.
• .
Central Processing Unit
Output
Devices
Cache
Memory
Primary
Storage
SecondaryStorageDevices
ControlUnit
ALU
Special
Purpose
Processors
Output
Devices
Input
Devices
• Storage device stores information to be recalled and used at a later time
• Storage device consists of:
•Storage medium
•Storage device
• Three major technology types for information storage:
•Magnetic
•Optical or laser
•Flash memory
• Storage devices hold data, even when the computer is turned
off.
• The physical material that actually holds data is called a
storage medium. The surface of a floppy disk is a storage
medium.
• The hardware that writes data to or reads data from a storage
medium is called a storage device. A floppy disk drive is a
storage device.
• The two primary storage technologies are magnetic and
optical.
• Diskettes (floppy disks) (FDD)
• Hard disks (HD)
• High-capacity floppy disks (ZIP Disk)
• USB flash drive
• Magnetic tape
• Compact Disk Read-Only Memory (CD-
ROM)
• Digital Video Disk Read-Only Memory
(DVD-ROM)
• CD-Recordable (CD-R)
• CD-Rewritable (CD-RW)
• Purpose:
– Long-term, nonvolatile storage
– Large, inexpensive, slow level in the storage hierarchy
• Disk composition
– A magnetic disk consist of a collection of platters (1to 20 per
disk) that rotate on a spindle.
– Disk surface divided into tracks (1000 to 4800 per platter).
– Tracks are divided into sectors (64 per track), which are the
smallest unit that can be read or written.
• Up to 15,000 rpm
• A read/write head travels across a spinning
magnetic disk, retrieving or recording data
• An optical disk is a high-capacity storage medium. An
optical drive uses reflected light to read data.
• To store data, the disk's metal surface is covered with tiny
dents (pits) and flat spots (lands), which cause light to be
reflected differently.
• When an optical drive shines light into a pit, the light
cannot be reflected back. This represents a bit value of 0
(off). A land reflects light back to its source, representing a
bit value of 1 (on).
• CD-ROM: compact disc ROM (Read Only Memory)
– Capacity: 650MB
• CD-R: compact disc recordable
• CD-RW: compact disc rewritable
• DVD: digital versatile disc
– Capacity: 4.7GB – 17GB
• DVD-R
• DVD-RW
• An optical disk is a high-capacity storage medium. An
optical drive uses reflected light to read data.
• To store data, the disk's metal surface is covered with tiny
dents (pits) and flat spots (lands), which cause light to be
reflected differently.
• When an optical drive shines light into a pit, the light
cannot be reflected back. This represents a bit value of 0
(off). A land reflects light back to its source, representing a
bit value of 1 (on).
• An optical disk is a high-capacity storage medium. An
optical drive uses reflected light to read data.
• To store data, the disk's metal surface is covered with tiny
dents (pits) and flat spots (lands), which cause light to be
reflected differently.
• When an optical drive shines light into a pit, the light
cannot be reflected back. This represents a bit value of 0
(off). A land reflects light back to its source, representing a
bit value of 1 (on).
• Input device captures information and translates it into a form that can be processed and used by other parts of your computer. •Keyboards
•Pointing devices
•Game controllers
•Scanners
•Styluses
•Microphones
•Digital cameras
•Web cams
• The keyboard is the most common input device. Types of keyboards include:
• Wireless
• Multimedia and one-touch access
• Portable keyboards for PDAs
Types of Input Devices
• Pointing devices are mainly used to choose and enter commands
• Pointing devices tend to have PS/2 connectors or USB connectors
• PS/2 connector fits into a PS/2 port, which a small round socket with small holes that fit the pins on the connector
• USB connectors fit into USB ports, and these are small rectangular openings on the back or front of your computer, or even on your keyboard or monitor
• Various pointing devices are available
• Types of pointing devices:
• Mouse
•Mechanical mouse
•Optical mouse
•Wireless mouse
• Trackball
• Touchpad
• Pointing stick
• Game controllers are used mainly to play games
• Types of gaming devices
• Gamepads
• Joysticks
• Gaming wheels
• Force feed
• Other types of input devices include:
• Scanners
• Styluses
• Microphones
• Digital cameras
• Web cams
•Scanner is a light sensitive device that helps you
copy or capture images, photos, and artwork
that exist on paper. Types of scanners include:
•Flatbed
• Stylus is an input device consisting of a thin
stick that uses pressure to enter information
or to click and point
• Styluses are used with:
•PDAs
•Tablet PCs
•Graphics tablets
• Microphones are used to input audio
• Three main types of microphones are:•Desktop microphones
•Headsets
•Directional microphones
• Speech recognition is increasingly being included in application software
Digital Cameras• Digital cameras are used to: • Download images to a computer
• Post pictures to the Web
• Produce videos
• Resolution is measured in megapixels
• Higher the resolution, better the image quality, but the more expensive the camera
• Web cam is a video camera
that can be used to take images
for uploading to the Web
• Output devices take information within your computer and present it to you in a form that you can understand
• Main output devices:
– Monitors
– Printers
– Speakers
• Devices with flat-panel displays
• Tablet PCs
• PDAs
• Cellular phones
• Desktop computers
• CRTs
• Flat-panel displays
– Gas plasma
– LCD (liquid crystal display)• Passive matrix
• Active matrix– Called TFT (thin film transistor)
– Separate transistor for every pixel
• Screen size measured as a diagonal line across the screen – from corner to opposite corner
• Resolution the number of pixels displayed on the screen (the higher the resolution, the closer together the dots)
• Pixels (or picture element) dots that make up the image on your screen
• Dot pitch is the distance between the centers of a pair of like-colored pixels
• Refresh rate the speed with which a monitor redraws the image of the screen, and is measured in hertz
©2003 The McGraw-Hill Companies
• Inkjet – most popular
– Makes images by forcing droplets
through nozzles
– Top speed is 20 pages per minute
• Laser
– Forms images using an
electrostatic process
– Prints between 3 and 30 pages per
minute
• Resolution of a printer is the
number of dots per inch (dpi) it
produces.
• Higher the resolution, better the
image, and usually the more
costly the printer
Printers - Cont. • Multifunction printer:
• Scan, copy, fax, and print
• Can be either inkjet or laser
• Cost less than buying
individual units
• Take up less desk space
• A speaker is a device that produces computer output as sound
• Speakers are common devices in computer systems Examples include:
• Built-in speaker
• Two-device set speakers
• Surround sound speakers
• Data Projector
Projects the image onto a wall screen.