Using Information Technology Williams/Sawyer ©2003 The McGraw-Hill Companies Chapter 5 Lecture Outline Section 5.1 Microchips, Miniaturization, & Mobility From Vacuum Tubes to Transistors to Microchips The ENIAC was the last computer to use vacuum tubes, in 1946. The ENIAC employed 18,000 vacuum tubes; unfortunately, a tube failure occurred every 7 minutes and it took more than 15 minutes to find and replace the faulty tube. A transistor is essentially a tiny electrically operated switch that can alternate between “on” and “off” many millions of times per second. The first transistors were one-hundredth the size of a vacuum tube, needed no warm-up time, consumed less energy, and were faster and more reliable. Transistors marked the beginning of a process of miniaturization that has not ended yet. Today more than 3 million transistors can be squeezed into a half centimeter. Today, transistors are part of an integrated circuit—an entire electronic circuit, including wires, formed on a single “chip,” or piece, of special material, usually silicon. An integrated circuit embodies what is 1 Using Information Technology Williams/Sawyer ©2003 The McGraw-Hill Companies called solid-state technology. Solid state means that the electrons are traveling through solid material—in this case, silicon. Silicon is an element that is widely found in clay and sand. It is used not only because its abundance makes it cheap but also because it is a semiconductor. A semiconductor is material whose electrical properties are intermediate between a good conductor of electricity and a nonconductor of electricity. A chip, or microchip, is a tiny piece of silicon that contains millions of microminiature electronic circuit components, mainly transistors. Miniaturization Miracles: Microchips, Microprocessors, & Micromachines Microchips—“industrial rice,” as the Japanese call them—are responsible for the miniaturization that has revolutionized consumer electronics, computers, and communications. They store and process data in all the electronic gadgetry we’ve become accustomed to. There are different kinds of microchips: microprocessor, memory, logic, communications, graphics and math coprocessor chips. Perhaps the 2 Using Information Technology Williams/Sawyer ©2003 The McGraw-Hill Companies most important is the microprocessor chip. A microprocessor (“microscopic processor” or “processor on a chip”) is the miniaturized circuitry of a computer processor—the part that processes, or manipulates, data into information. When modified for use in machines other than computers, microprocessors are called microcontrollers, or embedded computers. Mobility In the 1980s portability, or mobility, meant trading off computing power and convenience in return for smaller size and weight. Today, however, we are getting close to the point where we do not have to give up anything. Experts have predicted that small, powerful, wireless personal electronic devices will transform our lives far more than the personal computer has done so far. Section 5.2 The System Unit The Binary System: Using Two States 3 Using Information Technology Williams/Sawyer ©2003 The McGraw-Hill Companies Binary system has only two digits: 0 and 1. In the computer, the 0 can be represented by the electrical current being off and the 1 by the current being on. All data and programs that are used by a computer are represented in terms of these binary numbers. Capacity is denoted by any of the following: Bit: In the binary system, each 0 or 1 is called a bit, which is short for “binary digit.” Byte: A group of eight bits is called a byte, and a byte represents one character, digit, or other value. Kilobyte: A kilobyte (K, KB) is about 1000 bytes. (Actually, it’s precisely 1024 bytes, but the figure is commonly rounded.) The kilobyte was a common unit of measure for memory or secondarystorage capacity in older computers. Megabyte: A megabyte (M, MB) is about 1 million bytes (1,048,576 bytes). Most measures of microcomputer primary storage capacity today are expressed in megabytes. 4 Using Information Technology Williams/Sawyer Gigabyte: A gigabyte ©2003 The McGraw-Hill Companies (G, GB) is about 1 billion bytes (1,073,741,824 bytes). This measure was formerly used with “big iron” types of computers, but now is typical of secondary storage (hard disk) capacity of today’s microcomputers. Terabyte: A terabyte (T, TB) represents about 1 trillion bytes (1,009,511,627,776 bytes). Petabyte: A petabyte (P, PB) represents about 1 quadrillion bytes (1,048,576 gigabytes). ASCII: Pronounced “askey,” ASCII stands for American Standard Code for Information Interchange and is the binary code most widely used with microcomputers. EBCDIC: Extended Binary Coded Decimal Interchange Code—is used with large computers, such as mainframes. Unicode uses two bytes (16 bits) for each character, rather than one byte (8 bits). Instead of the 256 character combinations of ASCII-8, Unicode can handle 65,536 character combinations, thus allowing almost all the written languages of the world to be represented using a single character set. 5 Using Information Technology Williams/Sawyer ©2003 The McGraw-Hill Companies The Parity Bit Dust, electrical disturbance, weather conditions, and other factors can cause interference in a circuit or communications line that is transmitting a byte. A data error can be detected by using a parity bit. A parity bit, also called a check bit, is an extra bit attached to the end of a byte for purposes of checking for accuracy. Parity schemes may be even parity or odd parity. Machine Language Machine language is a binary-type programming language that the computer can run directly. To most people, an instruction written in machine language, consisting only of 0s and 1s, is incomprehensible. To the computer, however, the 0s and 1s represent precise storage locations and operations. The Computer Case: Bays, Buttons, & Boards The system unit houses the motherboard (including the processor chip and memory chips), the power supply, and storage devices. In 6 Using Information Technology Williams/Sawyer ©2003 The McGraw-Hill Companies computer ads, the part of the system unit that is the empty box with just the power supply is called the case or system cabinet. A bay is a shelf or opening used for the installation of electronic equipment, generally storage devices such as a hard drive or DVD drive. A computer may come equipped with four or seven bays. A tower is a cabinet that is tall, narrow, and deep. Power Supply The power supply is a device that converts AC current (electricity available from a standard wall outlet) to DC current to run the computer. Because electricity can generate a lot of heat, a fan inside the computer keeps the power supply and other components from becoming too hot. The three principal types of power protection devices are: Surge protector: is a device that protects a computer from being damaged by momentary surges (spikes) of high voltage. Voltage regulator: is a device that protects a computer from being damaged by insufficient power—“brownouts” or “sags” in voltage. 7 Using Information Technology Williams/Sawyer ©2003 The McGraw-Hill Companies UPS: (uninterruptable power supply) is a battery-operated device that acts as a surge protector and provides a computer with electricity if there is a power failure. The Motherboard & Microprocessor Chip The motherboard, or system board, is the main circuit board in the system unit. The motherboard consists of a flat board that fills one side of the case. It contains both soldered, nonremovable components and sockets or slots for components that can be removed—microprocessor chip, RAM chips, and various expansion cards. Expansion is a way of increasing a computer’s capabilities by adding hardware to perform tasks that are beyond the scope of the basic system. For example, you might want to add video and sound cards. Upgrading means changing to newer, usually more powerful or sophisticated versions, such as more powerful microprocessors or more memory chips. CISC (complex instruction set computing) chips, which are used mostly in PCs and in conventional mainframes, can support a large number of instructions, but at relatively low processing speeds. 8 Using Information Technology Williams/Sawyer ©2003 The McGraw-Hill Companies RISC (reduced instruction set computing) chips, which are used mostly in workstations, a great many seldom-used instructions are eliminated. As a result, workstations can work up to 10 times faster then most PCs. Processing Speeds: From Megahertz to Picoseconds For microcomputers—megahertz and gigaherz: Micro-computer microprocessor speeds are usually expressed in megahertz (MHz), millions of machine cycles per second, which is also the measure of a microcomputer’s clock speed. A high-end microcomputer or workstation might perform at 100 MIPS or more, a mainframe at 200–1200 MIPS. The latest generation of processors operates in gigahertz (GHz)—a billion cycles per second. Intel’s latest chip, the Pentium 4, operates at 1.4 gigahertz. For workstations, minicomputers, and mainframes—MIPS: Processing speed can also be measured according to the number of instructions processed per second that a computer can process, which today is in the millions. MIPS is a measure of a computer’s 9 Using Information Technology Williams/Sawyer ©2003 The McGraw-Hill Companies processing speed; MIPS stands for millions of instructions per second that the processor can perform. For supercomputers—flops: The abbreviation flops stands for floating-point operations per second, a floating-point operation being a special kind of mathematical calculation. This measure is expressed as megaflops (mflops, or millions of floating-point operations per second), gigaflops (gflops, or billions), and teraflops (tflops, or trillions). For all computers—fractions of a second: Another way to measure cycle times is in fractions of a second. A microcomputer operates in microseconds, a supercomputer in nanoseconds or picoseconds—thousands or millions of times faster. How the Processor or CPU Works: Control Unit, ALU, & Registers Word size: the number of bits that the processor may process at any one time. CPU (central processing unit) is the “brain” of the computer; it follows the instructions of the software (program) to manipulate data into information. 10 Using Information Technology Williams/Sawyer ©2003 The McGraw-Hill Companies How Memory Works: RAM, ROM, CMOS, & Flash RAM chips—to temporarily store program instructions and data: Primary storage is temporary or working storage and is often called memory or main memory; secondary storage is relatively permanent storage. RAM (random access memory) chips are for primary storage; they temporarily hold (1) software instructions and (2) data before and after it is processed by the CPU. Because its contents are temporary, RAM is said to be volatile—the contents are lost when the power goes off or is turned off. ROM chips—to store fixed start-up instructions: Unlike RAM, to which data is constantly being added and removed, ROM (readonly memory) cannot be written on or erased by the computer user without special equipment. ROM chips contain fixed start-up instructors—programs that are built in at the factory—that are necessary for basic computer operations. 11 Using Information Technology Williams/Sawyer ©2003 The McGraw-Hill Companies CMOS chips—to store flexible start-up instructions: CMOS (complementary metal-oxide semiconductor) chips are powered by a battery and thus don’t lose their contents when the power is turned off. Flash memory chips—to store flexible programs: Also a nonvolatile form of memory, flash memory chips can be erased and reprogrammed more than once, and do not require a battery. How Cache Works: Level 1 (Internal) & Level 2 (External) Cache temporarily stores instructions and data that the processor is likely to use frequently. Thus, cache speeds up processing. There are two kinds of cache—Level 1 and Level 2: Level 1 (L1) cache—part of the microprocessor chip: Level 1 (L1) cache, also called internal cache, is built into the processor chip. Its capacity is less than that of Level 2 cache, although it operates faster. 12 Using Information Technology Williams/Sawyer ©2003 The McGraw-Hill Companies Level 2 (L2) cache—not part of the microprocessor chip: Level 2 (L2) cache, also called external cache, resides outside the processor chip and consists of SRAM chips. Other Methods of Speeding Up Processing: Interleaving, Bursting & Pipelining Interleaving: a process in which the CPU alternated communciation between two or more memory banks. Bursting: Provides the CPU with additional data from memory based on the likelihood that it will be needed. Pipelining: Divides a task into a series of stages with some of the work completed at each stage. Ports & Cables Port: A connecting socket or jack on the outside of the system unit into which are plugged different kinds of cables. A port allows you to plug in a cable or connect a peripheral device, such as a monitor, printer, or modem, so that it can communicate with the computer system. Ports are of several types: 13 Using Information Technology Williams/Sawyer ©2003 The McGraw-Hill Companies Serial ports: for transmitting slow data over long distances: A line connected to a serial port will send bits one after another, like cars on a one-lane highway. Parallel ports—for transmitting fast data over short distances: A line connected to a parallel port allows 8 bits (1 byte) to be transmitted simultaneously. SCSI ports—for transmitting fast data to up to seven devices in a daisy chain: A SCSI (small computer system interface) port allows data to be transmitted in a “daisy chain” to up to 7 devices at speeds (32 bits at a time) higher than those possible with serial and parallel ports. USB ports—for transmitting data to up to 127 devices in a daisy chain: A USB (universal serial bus) port can theoretically connect up to 127 peripheral devices daisy-chained to one general-purpose port. Plug and Play, which allows peripheral devices and expansion cards to be automatically configured while they are being installed. 14 Using Information Technology Williams/Sawyer ©2003 The McGraw-Hill Companies Dedicated ports—for keyboard, mouse, phone, and so on: The back of a computer also has other, dedicated ports—ports for special purposes. Among these are the round ports for connecting the keyboard and the mouse. There are also jacks for speakers and microphones and modem-to-telephone jacks. Finally, there is one connector that is not a port at all—the power plug socket, into which you insert the power cord that brings electricity from a wall plug. Infrared ports—for cableless connections over a few feet: An infrared port allows a computer to make a cableless connection with infrared-capable devices. Expandability: Buses & Cards Expansion slots are sockets on the motherboard into which you can plug expansion cards. Expansion cards—also known as expansion boards, adapter cards, interface cards, plug-in boards, controller cards, add-ins, or add-ons— are circuit boards that provide more memory or that control peripheral devices. The following are all types of expansion cards: 15 Using Information Technology Williams/Sawyer ©2003 The McGraw-Hill Companies Graphics cards—for monitors Sound cards—for speakers and audio output Modem cards—for remote communication via phone lines Network interface cards—for remote communication via cable PC Cards—for laptop computers Section 5.3 Secondary Storage Floppy Disks Floppy disk, often called a diskette or simply a disk, is a removable flat piece of mylar plastic packaged in a 3.5-inch plastic case. 3.5-inch floppy disks—1.44 megabytes Zip disks—100 megabytes SuperDisks—120 megabytes HiFD disks—200 megabytes Hard Disks 16 Using Information Technology Williams/Sawyer ©2003 The McGraw-Hill Companies Hard disks are thin but rigid metal platters covered with a substance that allows data to be held in the form of magnetized spots. A head crash happens when the surface of the read/write head or particles on its surface come into contact with the surface of the harddisk platter, causing the loss of some or all of the data on the disk. There are two types of hard disks—nonremovable and removable. Hard-Disk Technology for Large Computer Systems Three types of secondary-storage devices are available for large computers: Removable packs: A removable-pack hard-disk system contains 6–20 hard disks, of 10.5- or 14-inch diameter, aligned one above the other in a sealed unit. Capacity varies; some packs range into the terabytes. Fixed-disk drives: Fixed-disk drives are high-speed, high-capacity disk drives that are housed (sealed) in their own cabinets. 17 Using Information Technology Williams/Sawyer ©2003 The McGraw-Hill Companies RAID storage system: A RAID (redundant array of inexpensive disks) storage system, which consists of two or more disk drives within a single cabinet or connected along a SCSI chain, sends data to the computer along several parallel paths simultaneously. Optical Disks: CDs & DVDs An optical disk is a removable disk, usually 4.75 inches in diameter and less than one-twentieth of an inch thick, on which data is written and read through the use of laser beams. Some optical disks are used strictly for digital data storage, but many are used to distribute multimedia programs that combine text, visuals, and sound. Among the types of optical disks are the following: CD-ROM—for reading only: CD-ROM (compact disk read-only memory) CD-R—for recording on once: CD-R (compact disk–recordable) disks CD-RW—for rewriting many times: A CD-RW (compact disk– rewritable) disk DVD-ROM—the versatile video disk: A DVD-ROM (digital versatile disk or digital video disk, with read-only memory) 18 Using Information Technology Williams/Sawyer ©2003 The McGraw-Hill Companies Magnetic Tape Magnetic tape is thin plastic tape coated with a substance that can be magnetized. Data is represented by magnetized spots (representing 1s) or nonmagnetized spots (representing 0s). Smart Cards Smart cards: A smart card looks like a credit card but contains a microprocessor and memory chip. When inserted into a reader, it transfers data to and from a central computer. Smart cards can be used as telephone debit cards. Optical cards: Optical cards are plastic, laser-recordable, wallettype cards used with an optical-card reader. Flash Memory Cards Flash memory cards, or flash RAM cards, consist of circuitry on creditcard-size cards that can be inserted into slots connecting to the motherboard. Flash memory cards are not infallible. Their circuits wear out after repeated use, limiting their lifespan. Still, unlike conventional 19 Using Information Technology Williams/Sawyer ©2003 The McGraw-Hill Companies computer memory (RAM or primary storage), flash memory is nonvolatile. Online Secondary Storage If the network computer or thin-client computer actually becomes as popular as its promoters hope, the Internet itself will become, in effect, your hard disk. When you sign up with a service, you usually download from a Web site free software that lets you upload whatever files you wish to the company’s server. For security, you are given a password, and the files are supposedly encrypted to guard against anyone giving them an unwanted look. Section 5.4 Future Developments in Processing & Storage DSP Chips: Processors for the Post-PC Era Digital signal processors (DSPs) are integrated circuits designed for high-speed data manipulation and used in audio, communications, and image manipulation. DSPs are designed to manipulate digital signals in speech, music, and video. 20 Using Information Technology Williams/Sawyer ©2003 The McGraw-Hill Companies Nanotechnology A nanometer is a billionth of a meter, which means we are operating at the level of atoms and molecules. Optical Computing Tomorrow’s computer might be optical, or opto-electronic—using light, not electricity. With optical technology, a machine using lasers, lenses, and mirrors would represent the on/off codes of data with pulses of light. DNA Computing Potentially, biotechnology could be used to grow cultures of bacteria that, when exposed to light, emit a small electrical charge, for example. The properties of this “biochip” could be used to represent the on/off digital signals used in computing. Quantum Computing 21 Using Information Technology Williams/Sawyer ©2003 The McGraw-Hill Companies Sometimes called the “ultimate computer,” the quantum computer is based on quantum mechanics, the theory of physics that explains the erratic world of the atom. A quantum computer stores information by using states of elementary particles. Scientists envision using the energized and relaxed states of individual atoms to represent data. Other Possibilities: Molecular & Dot Computers In the molecular computer, the silicon transistor is replaced with a single molecule. In the dot computer, the transistor is replaced by a single electron. These two approaches face formidable technical problems, such as mass-producing atomic wires and insulators. No viable prototypes yet exist. Future developments in secondary storage Greater Secondary Storage: Higher-Density Disks Higher densities allow disks to be packaged in smaller sizes. In 2000, IBM tripled the capacity of its silver-dollar-size removable hard drive from 340 megabytes to 1 gigabyte. The Microdrive, as it’s called, is designed for digital cameras, MP3 players, and handheld PCs. 22 Using Information Technology Williams/Sawyer ©2003 The McGraw-Hill Companies Molecular Electronics: Storage at the Subatomic Level Holograms as storage: A hologram is a three-dimensional picture created by two lasers. Dark and light areas of the hologram in a crystal could be used to code binary information. In the future, holograms could replace not only hard-disk drives but also memory chips. Molecular magnets as storage: Researchers have succeeded in creating a microscopic magnet, one molecule in size, derived from a special combination of materials (manganese, oxygen, carbon, and hydrogen). Subtomic lines as storage: Physicists at NEC in Tokyo used a tool called a scanning tunneling microscope (STM)—to paint and erase tiny lines roughly 20 atoms thick. Bacteria as storage: Scientists have reported research involving use of bacteria to store data in three dimensions. The Age of “Storewidth” The arrival of broadband communication is sure to exacerbate the demand for storage, “with billions of bytes of digital video and graphical 23 Using Information Technology Williams/Sawyer ©2003 The McGraw-Hill Companies data begging for storage space,” suggests one account. Technology guru George Gilder already has a name for the future kind of storage: storewidth. 24