Chapter 6 Computer Architecture Lecture Notes PDF

Chapter 6 Computer Architecture  Objectives Computer Input and Output Devices Motherboard Machine cycle Memory vs. Storage Data Representation 2 4  Computer programmable, electronic device that accepts data, performs operations, presents the results, and ca...

Chapter 6 Computer Architecture  Objectives Computer Input and Output Devices Motherboard Machine cycle Memory vs. Storage Data Representation 2 4  Computer programmable, electronic device that accepts data, performs operations, presents the results, and can store the data or results Input—entering data into the computer Processing—performing operations on the data Output—presenting the results Storage—saving data, programs, or output for future use 5 6 ‫المكونات الداخلية للحاسب‬ ‫‪7‬‬ 7 8  Input Devices Keyboard (keys, size, layout) Mouse (mechanical, optical) Trackball, touchpad, mouse stick Microphone Scanner (OCR) Bar code reader Card reader 9 10 10 Monitor 11 Types of Monitors CRT Cathode-ray tube (CRT)– Resemble televisions; use picture tube technology; inexpensive, but they take up desk space and use a lot of energy. Liquid Crystal Display (LCD or flat- panel)– Cells sandwiched between two LCD transparent layers form images; used for notebook computers, PDAs, cellular phones, and personal computers; expensive, and they take up less desk space and use less energy than CRT monitors. 12 Monitor Specifications Screen size– The diagonal measurement of the screen surface in inches (15, 17, 19, 21). Resolution– The sharpness of the images on the screen determined by the number of horizontal and vertical pixels that the screen can display (800x600, 1024x768, 1600x1200). Dot pitch– The distance between each pixel on the screen measured in millimeters (.22mm,.25mm,.28mm). 13  Televisions as Monitors Televisions have low resolution; therefore, they produce poor quality computer output. An NTSC (National Television Standards Committee) converter is needed to connect a computer to a TV. High Definition Television (HDTV) is designed to use digital signals. Digital TVs enable interactive use. 14  Printers A printer is a peripheral device that produces a physical copy or hard copy of the computer’s output. Two basic types: – Impact printer – Nonimpact printer 15  Impact Printer Impact printer Dot-matrix An impact printer is a printer that has a print head that contacts the paper to produce a character. It uses ink ribbon. It is noisy, produces Near-letter quality printouts, and is not commonly used today. Dot-matrix– Pins are used to make characters. 16 Nonimpact Printer Inkjet Laser Two types of nonimpact printers: – Inkjet printer– Also called bubble-jet; makes characters by inserting dots of ink onto paper; – Laser printer works like a copier; quality determined by dots per inch (dpi) 17 Multifunction Printer A multifunction printer combines the functions of a nonimpact printer, scanner, fax machine, and copier in one unit. 18  Plotter A plotter is a printer that uses a pen that moves over a large revolving sheet of paper. It is used in engineering and map making. 19  Audio Output Sound card - Speakers Digital formats include WAV, MPEG, MP3, and MIDI. 20 22  Motherboard It holds and allows communication between many of the electronic components of a system, such as the central processing unit (CPU) and memory, and provides connectors for other peripherals. It is on the size of A4 paper, its color is green or gold. On which we can distinguish the following components: 23  Motherboard -RAM -Expansion Slots -Expansion Cards -Processor, on which a fan or a heat sink is mounted. -Battery -Power supply to convert the 200v ac to 3.3 v dc. -Clock, which generates series of pulses per second -Chip Sets -ROM -Connectors 24 25  Machine Cycle  Machine cycle: the amount of time needed to execute an instruction – Personal computers execute in less than one millionth of a second – Supercomputers execute in less than one trillionth of a second Each CPU has its own instruction set – those instructions that CPU can understand and execute 27 Four steps performed for each instruction 28  Memory vs. Storage Hard Drive RAM Memory Storage, also known as mass media or auxiliary storage, refers to the various media on which a computer system can store data. Storage devices hold programs and data in units called files. Files are stored in directories or folders. Memory is a temporary workplace where the computer transfers the contents of a file while it is being used. 28 29  Storage Devices Storage devices are: Hardware that is capable of retaining data when the electricity is turned off. Able to read (retrieve) data from a storage medium (disk/tape). Able to write (record) data to a storage medium. NEXT 30 SLIDE  Why is storage necessary? Storage: Retains data when the computer is turned off. Is cheaper than memory. Plays an important role during startup. Plays an input role when starting applications. Is needed for output. Devices can hold a large amount of data. NEXT 31 SLIDE  Types of Storage Technologies Sequential– Hardware that reads and writes data in a serial (one after the other) fashion. Random-Access– Hardware that reads and writes data without going through a sequence of locations. Magnetic– Hardware that uses disks or tapes that are coated with magnetic material. Optical– Hardware that uses laser beams to read data from plastic disks. Solid State– Devices that use nonvolatile memory chips to read and write data. 32  Sequential – Magnetic Storage Tape Backup Unit Random-Access – Magnetic Storage Floppy Drive Hard Drive Jaz Drive Zip Drive 33  Sequential – Optical Storage CD-ROM / DVD Drive Magnetic – Optical Storage Magneto-Optic (MO) Drive 34  Solid State Storage Memory Smart Card Stick CompactFlash Flash Memory Memory Micro Drive PC Card 35  The Storage Hierarchy Storage hierarchy consists of three levels. They are: Online storage– Also called primary storage, it is made up of the storage devices that are actively available to the computer system. User action is not required. Near-online storage– Also called secondary storage, it is not readily available to the computer system. The user performs an action, such as inserting a disk, to make it available. Offline storage– Also called tertiary storage or archival storage, it is not readily available to the computer system. Devices such as tape backup units store data for archival purposes. 36  Capacity and Speed of Storage Devices Floppy Disk Hard Drive CD ROM / DVD Capacity– 720 KB to Capacity– Up to 1 TB Capacity– CD-ROM 650 1.44 MB MB; DVD 17 GB Access Time– 6 to 12ms Access Time– 100ms Access Time– 80 to 800ms A storage device’s performance is measured by: Capacity– The number of bytes of data that a device can hold. Access Time– The amount of time, in milliseconds (ms), it takes for the device to begin reading data. 37  Disks and Disk Drives A disk or diskette is a portable storage medium. Disks are circular plastic disks coated with a magnetically sensitive film. Disks work with a disk drive. High-density floppy disks Floppy disks store 1.44 MB of data. SuperDisk and High FD disks store up to 250 MB of data and are downwardly compatible with floppy disks. 38  Disk Organization Track Sector Cluster A disk is formatted–that is, it is divided into tracks and sectors and a file allocation table (FAT) is created.  Track– circular band  Sector– pie shaped section  Cluster– two or more adjacent sectors  FAT– keeps track of specific locations of files 39  How Hard Disks Work Platter Read/Write head Hard disks are a high-speed, high-capacity storage devices. They contain metal disks called platters. They contain two or more stacked platters with read/write heads for each side. Hard disks can be divided into partitions to enable computers to work with more than one operating system. 40  Factors Affecting a Hard Disk’s Performance Seek time or positioning performance– How quickly the read/write head positions itself and begins transferring information. It is measured in milliseconds (ms). Spindle speed or transfer performance– How quickly the drive transfers data. It is measured in rotations per minute (RPM). Latency– The time it takes for the spinning platter to bring the desired data to the read/write head. It is measured in milliseconds (ms). 41  Removable Hard Disks Jaz Drive Removable hard disks contain platters that are enclosed in a cartridge which can be inserted or removed from a drive. They are used for data archiving and data backup. 42  Magnetic Tape Tape Backup Unit Magnetic tape backup units store large amounts of data that are not used frequently. They use a cassette-type reel-to-reel plastic tape. 43  CD-ROM Disks and Drives CD-ROM stands for Compact Disk-Read Only Memory. They are capable of storing 650 MB of data. They are used for storing operating systems, large application programs, and multimedia programs. 44  CD-R and CD-RW Disks and Recorders CD-R CD-RW Disks that can be read Disks that can be read and written to. and written to. Disks can only be Disks are erasable. written to “once”. Disks can be written to Drives that are capable many times. of reading and writing Drives that are capable data are needed. of reading, writing and erasing data are needed. 45  DVD-ROM Disks and Drives DVD stands for Digital Video Disk. They use technology similar to CD-ROM. They are capable of storing up to 17GB of data. Their data transfer rate is comparable to that of hard disk drives. DVD-RAM– Has the ability to read/write data. 46  Flash Memory Cards SmartMedia CompactFlash Memory Stick Flash memory card– A wafer-thin card used with cellular phones, MP3 players, and digital cameras. Types of flash memory cards:  SmartMedia card  CompactFlash card  Sony’s Memory Stick 47  Smart Cards Smart card– Credit card-sized device combining flash memory with a microprocessor. It is used as a credit card. They offer more functionality, greater convenience, and higher safety than credit cards. 48  MAGNITUDE PREFIXES Kilo 1,000 Mega 1,000,000 Giga 1,000,000,000 Tera 1,000,000,000,000 Milli 1 / 1,000 Micro 1 / 1,000,000 Nano 1 / 1,000,000,000 Pico 1 / 1,000,000,000,000 49  Data Representation Computers understand two things: on and off Data represented in binary form Binary (base 2) number system Contains only two digits, 0 and 1 Corresponds to two states, on and off 53  Representing Data Bit Byte Word 51  Bit Short for binary digit Two possible values: 0 and 1 Can never be empty Basic unit for storing data 0 means off, 1 means on 52  Byte A group of 8 bits Each byte has 256 (28) possible values For text, stores one character Can be letter, digit, or special character Memory and storage devices measured in number of bytes 53  Word The number of bits the CPU processes as a unit Typically a whole number of bytes The larger the word, the more powerful the computer Personal computers typically 32 or 64 bits in length 54  Coding Schemes Provide a common way of representing a character of data Needed so computers can exchange data Common Schemes ASCII EBCDIC Unicode 55  ASCII Stands for American Standard Code for Information Interchange Most widely used standard Used on virtually all personal computers 56