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INFORMATION SHEET NO. 1.1-4 COMPUTER COMPONENTS AND DEVICES
LEARNING OBJECTIVES:
After reading this Information Sheet, you should be able to:
1. Classify of the hardware and software components of a computer with its corresponding functions.
2. Determine the various computer components and peripherals
A computer system is a special subsystem of an organization's overall information system. It is an integrated assembly of devices, centered on at least one processing mechanism utilizing digital electronics, which are used to input, process, store, and output data and information.
Putting together a complete computer system, however, is more involved than just connecting computer devices. In an effective and efficient system, components are selected and organized with an understanding of the inherent tradeoffs between overall system performance and cost, control, and complexity.
CONCEPT DEVELOPMENT:
Basic Hardware Components of Computer System
Today, almost everyone in our information society has a basic understanding of what a computer is and what it can do. A contemporary computer system consists of a central processing unit, primary storage, secondary storage, input devices, output devices, and communications devices that work together with software to perform calculations, organize data, and communicate with other computers.
A computer is an electronic machine, operating under the control of instructions stored in its own memory, that can be programmed to accept data (input), process it into useful information (output), and store it away in a secondary
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storage device (store) for safekeeping or later reuse. The processing of input into output is directed by the software but performed by the hardware. Figure below shows some common computer hardware components.
Common computer hardware components
Computer system hardware components include devices that perform the functions of input, processing, data storage; output and communication. The devices responsible for these five areas are as follows:
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Input devices. Input devices allow you to enter data or commands in a form that the computer can use; they send the data or commands to the processing unit. Commonly-used input devices include keyboard, mouse, microphone, scanner, digital camera, and PC camera.
Output devices. Output devices show people the processed data--information --in understandable and useful form. Four commonly used output devices are a printer, a monitor, speakers, and a portable media player. Input/output devices are playing an increasingly significant role in our lives. The number and variety of input/output devices are expanding.
Processing devices. Processing devices are the computer electronic circuitry housed in the system unit. The circuitry in the system unit is part of a circuit board called the motherboard. Two major components on the motherboard are the processor and memory. The processor, formally known as the central processing unit (CPU), has electronic circuitry that manipulates input data into the information people want. Computer instructions are actually are executed in the central processing unit.
Memory is a series of electronic elements that temporarily holds data and program instructions while they are being processed by the CPU. Both the processor and memory consist of chips. A chip is an electronic device that contains many microscopic pathways designed to carry electrical current.
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Storage devices. Storage usually means secondary storage that can store data and programs outside the computer itself. Storage devices hold data, information, and programs permanently. These devices supplement memory (also called primary storage) that can hold data and programs only temporarily. Common storage devices include a hard disk, USB flash drives, CDs, DVDs, and memory cards. A drive is a device that reads from and writes onto a storage medium. A storage medium is the physical material on which data, information, and program are stored. Some portable devices, such as digital cameras, use memory cards as the storage media.
Communications devices. Communications devices provide connections between the computer and communications networks, and enable computer users to communicate and to exchange data, information, and programs with other computers. Communications devices transmit these items over transmission media such as cables, telephone lines, satellites, and cellular radio. A widely used communications device is a modem.
In summary, we communicate with computers through input/output devices.
Input devices translate our data and communications into a form that the computer can understand. The computer then processes these data, and an output device translates them back into a form we can understand. The central processing unit manipulates data and controls the other parts of the computer system. Memory (primary storage) temporarily stores data and program instructions during processing, while secondary storage feeds data and instructions into the central processor and stores data for future use.
The System Unit The Motherboard
The system unit is a box-like case that houses the processor, memory and other electronic components of the computer that are used to process data. All other computer system devices, such as the monitor, keyboard, and mouse, are linked either directly or indirectly into the system unit.
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Figure below shows some of the components inside the system unit on a typical PC, including the processor, memory, expansion cards, drive bays, power supply, ports and connectors. The processor is the device that executes program instructions. The memory device is a package that holds temporarily data and program instructions during processing. An expansion card is a circuit board that adds devices or capabilities to the computer. Finally, devices outside the system unit, such as a keyboard, mouse, monitor, printer, or microphone, are attached by a cable to a port or connector on the system unit.
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To conserve on space, all-in-one computer houses the system unit in the same physical case as the monitor. On notebook computers, the keyboard and pointing device often occupy the area on the top of the system unit. The display attaches to the system unit by a hinge. The system unit on a handheld computer usually consumes the entire device. On these devices, the display is part of the system unit too.
When the cover of a system unit is removed, the motherboard, also called system board, can be seen inside the housing. The motherboard, a single circuit board, provides the path through which the processor communicates with memory components, other components, and peripheral devices. In a typical personal computer, the components attached to the motherboard include processor, memory chips, support electronic circuitry, and expansion boards. It is the processor that is the most important component of the motherboard.
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Many electronic components attach to the motherboard
A computer chip is a small piece of semi conducting material, usually silicon, on which one or more integrated circuits are etched. The various chips have standard-sized pin connectors that allow them to be attached to the motherboard and, there, to a common electrical path, called bus, that enables data flow between the various system components.
An integrated circuit (IC) contains many microscopic pathways capable of carrying electrical current. Each integrated circuit can contain millions of elements such as resistors, capacitors, and transistors. Transistors act as electronic switches that may or may not allow current to pass through. If current passes through, the switch is on, representing the 1 bit. If current does not pass through, the switch is off, representing a 0 bit. Thus, combinations of transistors can stand for combinations of bits, which represent numbers, letters, and other characters. The motherboard in the system unit contains many different types of chips. A miniaturized central processing unit can be etched on a chip, then the term computer on a chip.
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A central processing unit on a chip is called a microprocessor. On a personal computer, the central processing unit (CPU) usually is contained on a single chip. On the larger computers such as mainframes and supercomputer, the various functions performed by CPU are spread across many separate chips.
Today's popular Pentium microprocessor contains more than one hundred million transistors.
Ultimately, the type of processor and the amount of RAM placed on the motherboard define the computer’s speed and capacity. The processor is generally not made by the manufacturers of PCs. It is made by companies that specialized in the development and manufacture of microprocessors. A number of companies make microprocessors, including Intel, IBM, Motorola, Advanced Micro Devices (AMD), and Cyrix. Most chips are no bigger than one-half-inch square. Manufacturer’s package chips so the chips can be attached to a circuit board such as a motherboard, memory module, or adapter card.
A variety of chip packages exist. package holds a larger number of pins because the pins are mounted on the surface of the package. A flip chip-PGA (FC-PGA) package is a higher-performance PGA packaging that places the chip on the opposite side of the pins.
Another high performance packaging technique does not use pins. A single edge contact (SEC) cartridge connects to the
motherboard on one of its edges. Some common chip packages
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The Central Processing Unit
The central processing unit (CPU), also called processor, interprets and carries out the basic instructions that operate a computer. The CPU significantly impacts overall computing power and manages most of a computer's operations.
On larger computers, such as mainframes and supercomputers, the various functions performed by the processor extend over many separate chips and often multiple circuit boards. On a personal computer, all functions of the processor usually are on a single chip.
Most processor chip manufacturers now offer multi-core processors. A multi-core processor is a single-chip with two or more separate processors. Two common multi-core processors used today are dual-core and quad-core. A dual-core processor is a chip that contains tow separate processors. Similarly, a quad-core processor is a chip with four-separate processors. Each processor on a multi-core chip generally runs at a slower clock speed than a single-multi-core processor, but multi-core ships typically increase overall performance.
Memory
While performing a processing operation, a processor needs a place to temporarily store instructions to be executed and the data to be used with those instructions. The CPU cannot process data on an input device or disk directly;
the data must first be available in memory. A computer's memory in the system unit, located physically close to the CPU (to decrease access time), provides the CPU with a working storage area for program instructions, data and information.
Memory is also known as primary storage or internal storage. Memory usually consists of one or more chips on the motherboard or some other circuit board in the computer.
The major feature of memory is that it rapidly provides the instructions and data to the CPU. Memory stores three basic categories of items: (1) the operating system and other system software that control or maintain the computer and its devices; (2) application programs that carry our a specific task such as word processing; and (3) the data being processed by the application programs and resulting information.
This role of memory to store both data and programs is known as the stored program concept.
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Memory and storage sizes
Programs and data are placed in memory before processing, between processing steps, and after processing has ended, prior to being returned to secondary storage or released as output. Recall that a character is stored in the computer as a group of 0s and 1s, called a byte. Thus, a byte is the basic storage unit in memory. Like the CPU, memory components contain thousands of circuits imprinted on a silicon chip. Each circuit is either conducting electrical current (on) or not (off). By representing data as a combination of on or off circuit states, the data is stored in memory. When application program instructions and data are transferred into memory from storage devices, each of bytes is placed in a precise location in memory, called an address. This address is simply a unique number identifying the location of the byte in memory. To access data or instructions in memory, the computer references the addresses that contain bytes of data. The size of memory is measured by the number of bytes available for use (Figure 4-17). A kilobyte of memory is equal to exactly 1,024 bytes. To make storage definitions easier to identify, computer users often round a kilobyte down to 1,000 bytes. A megabyte (MB) is equal to approximately 1 million bytes.
A gigabyte (GB) equals approximately 1 billion bytes. A terabyte (TB) is equal to approximately 1 trillion bytes.
The system unit contains two types of memory: volatile and nonvolatile. The contents of volatile memory are lost when the computer power is turned off. In nonvolatile memory, the combination of circuit states is fixed, and therefore the contents of nonvolatile memory are not lost when power is removed from the computer. RAM is the most common type of volatile memory. Examples of nonvolatile memory include ROM, flash memory and CMOS. The following sub-sections discuss these types of memory.
RAM
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Random Access Memory (RAM) is the memory chips that are mounted directly on the motherboard or mounted on peripheral cards that plug into the motherboard. The RAM chips consist of millions of switches that are sensitive to changes in electric current. When the computer is powered on, certain operating system files are loaded from a storage device such as a hard disk into RAM. These files remain in RAM as long as the computer is running. As additional programs and data are requested, they are read from storage into RAM. The processor acts upon the data while it is in RAM. During the running time, the contents of RAM may change as the program is executed.
RAM comes in many different varieties. Three basic types of RAM are dynamic RAM, static RAM, and magnetoresistive RAM. Dynamic RAM (DRAM) must be refreshed (or recharged) constantly by the CPU or it loses its contents. Many variations of DRAM chips exist, most of which are faster than the basic DRAM.
One type of DRAM is Synchronous DRAM (SDRAM), which is much faster than DRAM because it is synchronized to the system clock. Double Data Rate (DDR) SDRAM chips are eve faster than SDRAM chips because they transfer data twice for each clock cycle, instead of just once, and DDR2 and DDR3 are even faster than DDR. Dual channel SDRAM is faster than single channel SDRAM because it delivers twice the amount of data to the processor. Rambus DRAM (RDRAM) is yet another type of DRAM that is much faster than SDRAM because it uses pipelining techniques. Most personal computers today use some form of SDRAM chips or RDRAM chips.
Static RAM (SRAM) is faster and more reliable than any form of DRAM. The term static refers to the fact that it does not have to be re-energized as often as DRAM.
SRAM is much more expensive than DRAM, thus it is usually used for special purpose, such as used in cache.
A newer type of RAM, called magnetoresistive RAM (MRAM), stores data using magnetic charges instead of electrical charges. Manufacturers claim that MRAM has greater storage capacity, consumes less power, and has faster access times than electronic RAM. Also, MRAM retains its contents after power is removed from the computer, which could prevent loss of data for users. As the cost of MRAM declines, experts predict MRAM could replace both DRAM and SRAM.
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RAM chips usually are packaged on a small circuit board, called memory module, which is inserted into the motherboard (Figure 4-19). Three types of memory modules are SIMMs, DIMMs, and RIMMs. A single inline memory module (SIMM) has pins on opposite sides of the circuit board that connect together to form a single set of contacts. With a dual inline memory module (DIMM), the pins on opposite sides of the circuit board do not connect and thus form two sets of contacts. SIMMs and DIMMs typically hold SDRAM chips. A Rambus inline memory module (RIMM) houses RDRAM chips.
The amount of RAM a computer requires often depends on the types
of applications you plan to use on the computer. A computer only can manipulate data that is in memory. A computer needs a certain amount of memory to store programs, data, and information. The more RAM a computer has, the faster the computer will respond.
A software package usually indicates the minimum amount of RAM it requires.
If you want the application to perform optimally, typically you need more than the minimum specifications on the software package. The necessary amount of RAM varies according to the type of work you do and the type of software applications you are using. The amount of RAM on your computer determines how many programs and how much data a computer can handle at one time and thus affects overall performance. Generally, home users running Windows Vista and using basic application software such as word processing should have at least 1GB of RAM. Most business users who work with accounting, financial, or spreadsheet programs, and programs requiring multimedia capabilities should have 1 to 4 GB of RAM. Users creating professional Web sites or using graphics-intensive applications will want 4GB or more of RAM. The amount of RAM in computers purchased today ranges from 1GB to 64GB. In an advertisement, A memory module being inserted in a motherboard.
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manufacturers specify the maximum amount of RAM a computer can hold, for example, 1GB expandable to 2GB.
ROM
Read-only memory (ROM) refers to memory chips storing permanent data and instructions. That is, the items stored in ROM chips cannot be modified--hence,
Read-only memory (ROM) refers to memory chips storing permanent data and instructions. That is, the items stored in ROM chips cannot be modified--hence,