Computer Hardware History of computers Types of computer systems Hardware components and functions Computer peripherals Chapter 3

Electronic computers ENIAC – First generation of electronic computer, 1946 – Used vacuum tubes – Programmable – 5000 calculations per second Drawbacks: – size; It occupied more than 1,500 square feet of floor space – processing ability; it could process only one program or problem at a time.

Next wave of computing Second generation, late 1950s – Transistors replace the vacuum tubes – 200,000 to 250,000 calculations per second Third generation, mid 1960s – Integrated circuitry with miniaturization Fourth generation, 1971 – Further miniaturization of circuits – Increased in Multiprogramming and virtual storage Fifth generation, 1980s – Millions of calculations per second

Microcomputers 1975, first microcomputer – ALTAIR 8800, was programmed by flicking switches on the front. 1977, first personal computers 1979, Mass production of the Apple computer, the fastest selling PC so far. 1982, IBM introduces the PC which changes the market

Computer System Categories

Computer System Categories factors: – Size – Processing capability – Storage capacity – Computation complexity

Microcomputer Systems Personal Computer (PC) : microcomputer for use by an individual – Desktop – fit on an office desk – Laptop – small, portable PC Information Appliances: Hand-held microcomputer devices known as personal digital assistants (PDA) – E.g. Internet enabled cellular phones

Microcomputer Systems (Network Computers ) Network Computers : are low-cost, sealed microcomputers with no or minimal disk storage that are linked to the network. Users of these Computers depend primarily on network servers for their operating system and Web browser, application software, and data access and storage. Terminals: modified Network Computers depend on network servers for software, processing and storage. Example: transaction terminals : ATM ( automated teller machines) POS ( point-of sale )

Powerful Microcomputer Systems Workstation : a powerful Microcomputer, that support applications with heavy mathematical computing and graphics display demands, such as computer-aided design (CAD) in engineering or investment and portfolio analysis in the securities industry. Network Server : more powerful microcomputers that coordinate telecommunications and resource sharing in small networks such as local area networks (LANs).

Midrange systems E.g. High-end network servers: computers used to coordinate communications and manage resource sharing in network settings. E.g. Minicomputers for scientific research and industrial process monitoring and control. Less costly to buy, operate and maintain than mainframe

Mainframe Computer Systems Large, fast powerful computer systems – Can process thousands of million instructions per second (MIPS). Large primary storage capacity High transaction processing Complex computations E.g. superservers for large companies

Mainframe : Supercomputer Systems Extremely powerful systems Designed for Scientific, engineering and business applications at extremely high speeds Used for applications such as :Global weather forecasting, military defense, computational cosmology and astronomy, microprocessor research and design, and large-scale data mining Parallel processing with thousands of microprocessors Billions of operations per second (gigaflops) Supercomputers that calculate in teraflops (trillions of floating-point operations per second) which use thousands of microprocessors are now in use. Cost millions of dollars Minisupercomputers costing hundreds of thousands of dollars

Computer hardware functions

Input devices: – E.g. Keyboards, mice, optical scanners – Convert data into electronic form Processing device: – Central Processing Unit (CPU) consists of: Arithmetic-logic unit performs the arithmetic functions Control unit Output devices: – E.g. Video display units, printers, etc. – Convert electronic information into human- intelligible form

Computer hardware functions Storage devices: – Primary Storage Unit or main memory – E.g. RAM, cache memory – Secondary Storage E.g. Magnetic disks and Optical disks Control device: – Control unit of the CPU – Controls the other components of the computer

Computer Processing Speeds Time as speed unit Millisecond: thousandth of a second Microsecond: millionth of a second Nanosecond: billionth of a second Picosecond: trillionth of a second Number of Instructions per second as speed unit MIPS : million instructions per second Gigaflops: Billions of operations per second Teraflops: trillions of floating point operations per second (Supercomputer) Clock speed of the computer (the speed of microprocessors’ timing circuits or internal clock): Megahertz (MHz) : millions of cycles per second Gigahertz (GHz) : billions of cycles per second

Moore’s Law Moore observed an exponential growth (doubling every 18 to 24 months) in the number of transistors per integrated circuit and predicted that this trend would continue.

Peripherals Peripheral is generic name for all input, output, and secondary storage devices that are part of the computer system but are not part of the CPU Peripherals are online devices; they are separate from CPU But electronically connected to and controlled by CPU Offline devices: Separate from and not under control of the CPU

Peripheral Checklist

Input technologies Keyboards Pointing Devices Optical Scanning Digital cameras Speech Recognition Systems

Pointing Devices The Pointing Devices work with Graphical user interface (GUI) using point-and-click or point- and-drag methods. GUI (Graphical User Interface): Icons, menus, windows, buttons and bars

Pointing Devices (2) Electronic Mouse Trackball – Stationary device like a mouse – Roller ball used to move cursor on screen. Pointing Stick (also called a trackpoint) – Small eraser head-like device in keypad – Moves cursor in direction of pressure placed on stick. Touchpad – Small rectangular touch-sensitive surface – Moves the cursor in the direction of finger moves on the pad

Pointing Devices (3) Touch Screen – Pressure-sensitive Video display screen Pen-based Computing Used in Tablet PCs and PDAs like touch screen Contain fast processors and have software that digitizes handwriting, hand printing, and hand drawing

Optical Scanning Read text or graphics and convert them into digital input Optical Scanners: – Compact Desktop scanners (low cost and ease of use) – Flatbed scanners (larger, more expensive but faster and provide higher-resolution color scanning) Optical Character Recognition (OCR) Scanners : – an optical scanner with sophisticated software can read the characters and codes on printed or written text such as merchandise tags, product labels, credit card receipts, utility bills, airline tickets, and other documents. – E.g. handheld optical scanning wands that used to read bar codes such as the Universal Product Code (UPC)

Speech Recognition Systems System compares speech patterns to database of sound patterns. These systems require Training: to recognize your voice patterns; Training such systems involves repeating a variety of words and phrases used to operate your computer’s operating systems and software packages through voice input of data and commands. Speaker independent system: understand voice never heard before Used in voice-messaging computers Examples include computerized telephone call switching, telemarketing surveys, bank pay-by-phone bill-paying services, stock quotation services, university registration systems, and customer credit and account balance inquiries.

Output Technologies Video displays – Cathode ray tube (CRT) like a television old desktop PC screens – Liquid crystal displays (LCDs) Laptop and PDAs, PCs – Plasma Displays – LED Displays Printed Output – Inkjet printer: Spray ink on page – Laser printer : Electrostatic process like photocopying machine

Storage Devices Primary Storage Semiconductor Memory Secondary Storage Magnetic Disk Optical Disk Magnetic Tape Storage tradeoffs Factors Access Speed (Semiconductor, Magnetic Disk, Optical Disk, Magnetic Tape) Storage capacity (Magnetic Tape, Optical Disk, Magnetic Disk, Semiconductor) Cost (Semiconductor, Magnetic Disk, Optical Disk, Magnetic Tape)

Storage tradeoffs

Computer Storage Fundamentals Binary representation – Data are processed and stored in computer system through the presence or absence of signals or electronic charge. – Either ON or OFF ON = number 1 OFF = number 0

Bit and Byte Bit (short for binary digit) – Smallest element of data – Either zero or one Byte – Group of eight bits which operate as a single unit – Represents one character or number

Representing characters in bytes ASCII : (American Standard Code for Information Interchange)

Computers use binary system to calculate

Measuring storage capacities Kilobyte (KB): one thousand bytes; 1024 Byte exactly Megabyte (MB): one million bytes = 1024 KB Gigabyte (GB): one billion bytes = 1024 MB Terabyte (TB): one trillion bytes = 1024 GB Petabyte (PB): one quadrillion bytes = 1024 TB Exabyte (EB) : one quintillion bytes = 1024 PB

Direct and Sequential Access Direct Access or Random Access – Directly store and retrieve data – Each storage position has unique address and can be accessed in same length of time – Semiconductor memory chips, magnetic disks, optical disk Sequential Access – Data is stored and retrieved in a sequential process – Must be accessed in sequence by searching through prior data – Magnetic tape

Direct and sequential access

Semiconductor memory Microelectronic semiconductor memory chips Used for primary storage Advantage: – Small size – Fast (high access speed) – Shock and temperature resistance Disadvantage: – Volatility: must have uninterrupted electric power or lose memory

Two types of semiconductor memory RAM: random access memory – Most widely used primary storage medium – Volatile memory – Read/write memory ROM: read only memory – Permanent storage – Can be read but cannot be overwritten – Frequently used programs ( control instructions in the control unit and programs in primary storage such as parts of the operating system) permanently burnt in to the storage cells during manufacture. Variations include: – PROM (programmable read-only memory) – EPROM (erasable programmable read-only memory), which can be permanently or temporarily programmed after manufacture.

Flash drive New type of permanent storage Uses semiconductor memory Small chip with thousands of transistors Easily transported Also called jump drives, USB flash drives Source: Courtesy of Lexar Media.

Magnetic Disks Used for secondary storage Fast access and high storage capacity

Types of magnetic disks Floppy disks – Magnetic disk inside a plastic jacket Hard disk drives – Magnetic disk, access arms, and read/write heads in sealed module RAID (Redundant arrays of independent disks) – Disk arrays of interconnected hard disk drives – Fault tolerant with multiple copies on several disks

Magnetic Tape Secondary storage Tape reels and cartridges Main purpose of using Magnetic Tape is : Archival storage and backup storage

Optical Disks

Uses of optical disks Publishing medium for fast access to reference materials – Catalogs, directories, etc. Interactive multimedia applications – Video games, educational videos, etc.