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Midterm

Midterm 2 Summary.doc

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Department
Administrative Studies
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ADMS 2511
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Description
Technology Guide 1Computer HardwareDecisions about hardware focus on three interrelated factors Capability power and appropriateness for the task Speed and Cost Hardware refers to the physical equipment used for the input processing output and storage activities of a computer system It consists of the following oCentral processing unit CPU manipulates the data and controls the tasks performed by the other componentsoPrimary storage internal to the CPU temporarily stores data and program instructions during processing oSecondary storage external to the CPU stores data and programs for future useoInput technologies accept data and instructions and convert them to a form that the computer can understandoOutput technologies present data and information in a form people can understandoCommunication technologies provide for the flow of data from external computer networkseg the Internet and intranets to the CPU and from the CPU to computer networks Central Processing Unit CPUCentral processing unit CPU performs the actual computation or number crunching inside any computer The CPU is a Microprocessor Intel Pentium 4 or Centrino made up of millions of microscopic transistors embedded in a circuit on a silicon chipControl unit sequentially accesses program instructions decodes them and controls the flow of data to and from the ALU the registers the caches primary storage secondary storage and various output devicesArithmeticlogic unit ALU performs the mathematic calculations and makes logical comparisonsRegisters are highspeed storage areas that store very small amounts of data and instructions for short periods of timeThe CPU can process only Binary formdata and instructions only consists of 0 and 1 Machine instruction cycle The cycle of computerprocessing whose speed is measured in terms of thenumber of instructions a chip processes per second It occurs millions of times per second or more Processing speed depends on the following four factors of chip designClock speedthe preset speed of the computer clock that times all chip activities measured in megahertz MHz millions of cycles per second and gigahertz GHz billions of cycles per second The faster clock speed the faster the chip or computer speed Word length The number of bits 0s and 1s that can be processed by the CPU at any one time It can be 32bit or 64bit word lengths and the larger the word length the faster the chip or computer speed Bus width The size of the physical paths down which the data and instructions travel as electrical impulses on a computer chip The wider or bigger the bus the more data can be transferred and the faster the processing 1The number of transistors on the chip depend on the Line widththe distance between transistors in nanometres billionths of a meter The smaller the line width the more number of transistors on the chip and the faster the chip or computer speedMoores Law predicted in 1965 that microprocessor complexity would double approximately every two years his prediction has been amazingly accurate as a result of the following changes oIncreasing miniaturization of transistorsoDecreasing line widthmaking the physical layout of the chips components as compact and efficient as possibleoUsing materials for the chip that improve the conductivity flow of electricity eg gallium arsenide and silicon germanium oTargeting the amount of basic instructions programmed into the chip Tow most common microprocessor architectures are CISI complex instruction set computing and RISI Reduced instruction set computingoPlacing multiple processors on a single chipMulticore chips eg Intel Core 2 Duo or Intel DualCore Microcontrollers are computer chips embedded in products and technologies cell phone toys etc that usually cost less and work in lessdemanding applications than microprocessorsComputer MemoryThere are two basic categories of computer memory Primary Storage and Secondary Storage Primary stores small amounts of data and information that will be immediately used by the CPU Secondary stores much larger amounts of data and information an entire software program for example for extended periods of time Memory CapacityoBit Short for binary digit 0s and 1s the only data that a CPU can processoByte An 8bit string of data needed to represent any one alphanumeric character or simple mathematical operationoKilobyte KB approximately one thousand bytesoMegabyte MB approximately one million bytes 1048576 bytes or 1024 x 1024oGigabyte GB approximately one billion bytes actually 1073741824 bytes 1024 x 1024 x 1024 bytesoTerabyte approximately One trillion bytes15oPetabyte Approximately 10 bytes18oExabyte Approximately 10 bytesPrimary StoragePrimary storage or main memory stores three types of information for very brief periods of time 1Data to be processed by the CPU2Instructions for the CPU as to how to process the data3Operating system programs that manage various aspects of the computers operationPrimary storage takes place in chips mounted on the computers main circuit board called the motherboard All data and instructions in primary storage have been translated into binary code Four main types of primary storage 1Registers registers are part of the CPU with the least capacity storing extremely limited amounts of instructions and data only immediately before and after processing22Random Access Memory RAM The part of primary storage that holds a software program and small amounts of data when they are brought from secondary storage RAM is temporary and volatilelose data if power is off Two main type of RAM Dnaymic RAM DRAMslow but cheap and Static RAM SRAM fast but expensive Other type is Magnetic RAM MRAM less electricity consumed combined high speed of SRAM storage capacity of DRAM and the nonvolatility of flash memory 3Cache Memory A type of highspeed primary storage that enables the computer to temporarily store blocks of data that are used more often and that a processor can access more rapidly than main memory RAM There are three types of Cache memory Level 1 L1 Level 2 L2 Level 3 L3 L1 and L2 caches are located in the processor and L3 cache is located on motherboard L1 is smaller and faster than L2 which is in turn smaller and faster then L3 4ReadOnly Memory ROM Type of primary storage where certain critical instructions are safeguarded the storage is nonvolatile and retains the instructions when the power to the computer is turned off Flash memory is a form of rewritable readonly memory that is compact portable and requires little energySecondary StorageSecondary Storage is memory capacity that can store very large amounts of data for extended periods of time The overall trends in secondary storage are toward more directaccess methods higher capacity with lower costs and increase portability It has the following characteristics oIt is nonvolatileoIt takes much more time to retrieve data because of the electromechanical nature oIt is cheaper than primary storageoIt can take place on a variety of mediaMagnetic MediaMagnetic Tape is a secondary storage medium kept on a large open reel or in a smaller cartridge or cassette Its an old technology but popular because of its a cheapest storage medium and can handle enormous amounts of data However it uses the slowest method for retrieving data because the data are placed on the tape sequentially ie Sequential accessdata access in which the computer system must run through data in sequence in order to locate a particular piece So magnetic tape is best or data which rarely use or does not need immediate access to Magnetic Disks are a form of secondary storage on a magnetized disk divided into tracks and sectors that provide addresses for various pieces of data also called Hard Disks or Hard Drives a form of secondary storage that stores data on platters divided into concentric tracks and sectors which can be read by a readwrite head that pivots across the rotating disks Hard Disks are the most commonly used because of low cost high speed and large storage capacity Data stored and access in hard disks is Direct accessdata access in which any piece of data be retrieved in a nonsequential manner by locating it using the datas address Be aware of loss data occur by a disk crash Most PCs use two highperformance disk interface standards Enhanced Integrated Drive Electronic EIDE inexpensive good performance supports to 4 disks tapes or CDROM and Small Computer System Interface SCSI more expensive faster and support more devices more common uses for graphics serverbased or large database Magnetic diskettes or Floppy disks is a form of easily portable secondary storage on flexible Mylar disks Much slower than hard disks less capacity only 144 MB individually cheap but cost more in term of its small storage Big advantage is portable Optical Storage Devices3
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