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The components of a computer(Part I)
Overview : A computer
accepts data and processes it into useful information consists of
input: accepts data in machine-readable form and sends it to the processor.
Processor (CPU):executes computer instructions to turn the data into useful information.
Output:makes the machine-readable information available for users.
Storage:supplements main memory - diskettes, hard disk, CD-ROM, etc.
Main Components of a Computer
Secondary
Storage
Input Processing Output
Input
Input devices accept data and instructions from the user keyboard: you type in your input (the display screen is actually an
output device mouse:moves pointer on screen, pressing button invokes commands scanners: bar code readers, flat bed scanners, etc., captures codes,
photos, drawings, text into the computer directly writing tablets:reads hand-written Chinese characters data glove: captures gestures as well as 3D coordinates sensors:temperature, pressure,… card readers: one line of data/instruction per card
Processor
The central processing unit (CPU) is the brain of the computer
it transforms raw data into useful information it executes program instructions it consists of electronic circuits etched into silicon
or other material - a chip of a set of chips plugged into circuit boards
Memory
Computer memory, or primary storage, is not part of the CPU but closely associated with it
memory holds the program and the data being processes by the CPU while the data and program are in memory, the processor can
communicate with it directly this built-in memory is called random-access memory (RAM) the common unit of measures is the byte-8 bits - the amount needed to
store a single character (Chinese characters need more than 1 byte) common short-hands - kilobyte (KB) and megabyte (MB)
Output
Raw data processed into useable information 2 common devices are the display screen (monitor) and the
printer early monitors display only characters in one color, now
they can display any shape or symbols in virtually any color
printers produce printed material under the control of a program
Secondary Storage
Secondary storage is where the computer stores data and programs that it is not currently using
common media : magnetic disk and magnetic tape data in secondary storage cannot be accessed directly
(unlike main memory) but
they have larger capacity they retain their contents even when the computer is turned off they are much cheaper per unit
Common diskettes come in 2 sizes: 3-1/2 and 5-1/4 hard disks have large capacity and offer faster access time
then diskettes optical disks have much higher capacity, but cannot be
written on easily magnetic tape is similar to audio/video tapes, they are
inexpensive, but can only be accessed sequentially
MICROPROCESSORMICROPROCESSOR
Microprocessor Comparison Intel Pentium Intel Celeron AMD (Intel-compatible) Motorola PowerPC Alpha
MICROPROCESSORMICROPROCESSOR
Microprocessor Comparison Intel processors
• Xeon
• Pentium II with MMX
• Celeron
MICROPROCESSORMICROPROCESSOR
Processor Installation and Upgrades Zero-insertion force (ZIF) sockets Upgrades
• Chip for chip
• Piggyback
• Daughterboard
MICROPROCESSORMICROPROCESSOR
Coprocessors Special processor chip or circuit board designed
to assist the processor in performing specific tasks
Floating-point coprocessor
MICROPROCESSORMICROPROCESSOR
Parallel Processing Using multiple processors simultaneously to
execute a program Speeds execution Requires special software
Classes of Computers
Mainframes - very high speeds and very large data volumes
Minicomputers - a step down Super-minis Personal Computers(PC) - microcomputers Super-micros laptops - notebooks, runs on battery Sub-notebooks Pen-based Computers - personal digital assistants
Communication
Computers started out very large, with many dumb terminals connected
Gradually computers become smaller and smaller, with only one set of keyboard/monitor
These PCs need to communicate with one another, as well as mainframes
Again we have many PCs (intelligent terminals) connected to mainframe, or many mainframes
A Simple Computer Network
Processing have been decentralized, or distributed It becomes a networkBy far the most important network service is
electronic mailNow the Internet is rapidly gaining in importance