Hardware- Input, Processing, And Output Devices

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Hardware: Input, Processing, and Output Devices At a Glance

Overview In this chapter, we concentrate on the hardware component of a CBIS. Hardware consists of any machinery (most of which uses digital circuits) that assists in the input, processing, storage, and output activities of an information system. The overriding consideration in making hardware decisions in a business should be how hardware can be used to support the objectives of the information system and the goals of the organization.

Principles and Objectives Principles

Learning Objectives

Assembling an effective, efficient set of computer hardware devices requires understanding their role in supporting the underlying information systems and the needs of the organization. The computer hardware objectives are subordinate to, but supportive of, the information systems and the needs of the organization.

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When selecting computer hardware, you must consider the current and future needs of the information systems and the organization. Your choice of a hardware device should always allow for later improvements to meet evolving organizational needs.

Describe how to select and organize computer hardware components to support information system (IS) objectives and business needs.

• Describe the power, speed, and capacity of central processing and memory devices. • Describe the access methods, capacity, and portability of secondary storage devices. • Discuss the speed, functionality, and importance of input and output devices. • Identify popular classes of computer systems and discuss the role of each.

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Teaching Tips Why Learn About Hardware? Investing in computer hardware allows an organization to improve worker productivity, increase revenue, reduce costs, and provide better customer service. Managers in an organization, no matter what their career field and educational background, are expected to know enough about hardware to help define the business needs that the hardware must support. In addition, managers must be able to ask good questions and evaluate options when considering hardware investments for their area of the business.

Computer Systems: Integrating the Power of Technology A computer system is a special subsystem of an organization's overall information system. It is an integrated assembly of devices that 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, hardware devices are selected and organized with an understanding of the inherent trade-offs between overall system performance and cost, control, and complexity. When selecting hardware devices, you must consider the current and future uses to which the system will be put. Your choice of hardware should always allow for later improvements in the overall information system. Reasoned forethought is the hallmark of a true IS professional. Hardware Components The ability to process, organize, and manipulate data is a critical aspect of a computer system. Processing in a computer system is accomplished by interplay between one or more of the central processing units and primary storage. Each central processing unit (CPU) consists of three associated elements: the arithmetic/logic unit, the control unit, and the register areas. The arithmetic/logic unit (ALU) performs mathematical calculations and makes logical comparisons. The control unit sequentially accesses program instructions, decodes them, and coordinates the flow of data in and out of the ALU, the registers, primary storage, and even secondary storage and various output devices. Registers are high-speed storage areas used to temporarily hold small units of program instructions and data immediately before, during, and after execution by the CPU. The relationship between the different components is illustrated in Figure 3.1 on page 84, as shown below:

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Figure 3.1: Hardware Components

Primary storage, also called main memory or just memory, is closely associated with the CPU. It holds program instructions and data immediately before or immediately after the registers. Hardware Components in Action Executing any machine-level instruction involves two phases: instruction and execution. During the instruction phase, a computer performs the following steps: Step 1: Fetch instruction Step 2: Decode instruction During the execution phase, a computer performs the following steps: Step 3: Execute instruction Step 4: Store results

Processing and Memory Devices: Power, Speed, and Capacity The components responsible for processing, the CPU and memory, are housed together in the same box or cabinet, called the system unit. All other computer system devices, such as the monitor and keyboard, are linked either directly or indirectly in the system unit housing. Processing Characteristics and Functions Because efficient processing and timely output is very important to most organizations, a variety of measures are used to gauge processing speed. These measures include the time it takes to complete a machine cycle and clock speed.

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Memory Characteristics and Functions Located physically close to the CPU (to decrease access time), memory provides the CPU with a working storage area for program instructions and data. Its main feature is that it rapidly provides data and instructions to the CPU. Instructions or data can be temporarily stored in and read from random access memory (RAM), which is temporary and volatile as RAM chips lose their contents if the current is turned off or disrupted. Another type of memory, ROM, an acronym for read-only memory, is usually nonvolatile. In ROM, the combination of circuit states is fixed, and therefore its contents are not lost if the power is removed. It provides permanent storage for data and instructions that do not change, such as programs and data from the computer manufacturer. Cache memory is a type of high-speed memory that a processor can access more rapidly than main memory. Because it contains less data, the CPU can access the desired data and instructions more quickly than if it were selecting from the larger set in main memory. The CPU can thus execute instructions faster, and the overall performance of the computer system is raised. Multiprocessing One form of multiprocessing involves coprocessors. A coprocessor speeds processing by executing specific types of instructions while the CPU works on another processing activity. It can be internal or external to the CPU and may have a different clock speed from that of the CPU. Another form of multiprocessing involves a multicore microprocessor, which combines two or more independent processors into a single computer so that they can share the workload and boost processing capacity. A dual-core processor enables the user to perform multiple tasks simultaneously. Some processes, such as a medical CAT scan, require a multicore microprocessor. Parallel Computing Parallel computing is the simultaneous execution of the same task on multiple processors to obtain results faster. In massively parallel processing, hundreds and even thousands of processors are linked together to operate at the same time, or in parallel. Each processor includes its own bus, memory, disks, copy of the operating system, and application software.

Secondary Storage Organizations need to store large amounts of data, instructions, and information more permanently than allowed by main memory. As a result, secondary storage is used. Compared with memory, secondary storage offers the advantages of nonvolatility, greater capacity, and greater economy.

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Access Methods Data and information access can be either sequential or direct. Sequential access implies that data must be accessed in the order in which it is stored, while direct access means that data can be retrieved directly, without the need to pass by other data in sequence. The devices used to sequentially access secondary storage data are simply called sequential access storage devices (SASDs), and those used for direct access are called direct access storage devices (DASDs). Devices The most common forms of secondary storage include the following: magnetic tapes, magnetic disks, virtual tapes, and optical disks. Magnetic tape is inexpensive but slower in terms of finding and accessing data, while magnetic disks are somewhat faster and more expensive. Another storage choice, redundant array of independent/inexpensive disks (RAID), allows for the recovery of data in the event of failure. Optical technology includes compact disc read-only memory (CD-ROM), as well as CDrecordable (CD-R) and CD-rewritable (CD-RW) technologies. Other storage alternatives include digital video disc (DVD), memory cards, flash memory, and holographic discs. Enterprise Storage Options Businesses today need to store large amounts of data created throughout the organization. Such large secondary storage is called enterprise storage. Three forms of enterprise storage options that are commonly used are attached storage, network-attached storage (NAS), and storage area networks (SANs). In attached storage methods, tape, hard disks, and optical secondary storage devices are connected directly to a single computer. Attached storage methods are simple and cost effective for single users and small groups, but do not allow systems to share storage. Also, they make it difficult to back up data. The other two options for enterprise storage – NAS and SANs – offer a number of advantages over attached storage methods. They enable an organization to share datastorage resources among a much larger number of computers and users, resulting in improved storage efficiency and greater cost-effectiveness. In addition, they simplify data backup and reduce the risk of downtime. NAS employs storage devices that attach to a network instead of to a single computer. A SAN is a special-purpose, high-speed network that provides direct connections between data-storage devices and computers across the enterprise.

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Input and Output Devices: The Gateway to Computer Systems Characteristics and Functionality Getting data into the computer system is a two-stage process. First, human-readable data is converted into machine-readable form through a process called data entry. Secondly, the machine-readable data must be transferred into the system, a process known as data input. Regardless of how data gets into the computer however, it should be captured and edited at its source, a concept known as source data automation. Input Devices A keyboard and a computer mouse are the most common devices used for entry and input of data such as characters, text, and basic commands. Some companies are developing newer keyboards that are more comfortable, adjustable, and faster to use. Another type of input device can recognize human speech. Called voice-recognition devices, these tools use microphones and special software to record and convert the sound of the human voice into digital signals. Inexpensive and easy to use, terminals are input devices that perform data entry and data input at the same time. They allow general commands, text, and other data to be entered via a keyboard or mouse, converted into machine-readable form, and transferred to the processing portion of the computer system. Output Devices Computer systems provide output to decision makers at all levels of an organization to solve a business problem or capitalize on a competitive opportunity. In addition, output from one computer system can be used as input into another, within the same information system. Some monitors use a cathode-ray tube to display images; these are known as CRTs. Such a monitor works much the same way a traditional TV screen does. Liquid crystal display (LCD) monitors are flat displays that use liquid crystals to form characters and graphic images on a backlit screen. These displays have many advantages over CRTs because they are flicker-free, far lighter, less bulky, and do not emit the type of radiation that makes some CRT users worry.

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Special-Purpose Input and Output Devices There are many other input and output devices that are used for specialized or unique applications. One example is computer-based navigation systems, which are satellite-based radio navigation systems that can guide you to specified destinations. Another example is multiple-function printers that can copy, print (in color or black and white), fax, and scan. Yet another example is eyebud screens, which are portable media devices that display video in front of one eye.

Computer System Types, Selection, and Upgrading In general, computers can be classified as either special purpose or general purpose. Specialpurpose computers represent those used by military and scientific research groups, such as the CIA and NASA, for limited applications. General-purpose computers are used for a variety of applications and are the most common. Computer System Types Handheld computers are small (some as small as a credit card), portable, single-user computers. Handheld computers are sometimes referred to as personal digital assistants (PDAs). There are several types of portable computers – computers that can be carried easily. These include laptops, notebooks, subnotebooks, and tablet computers. Thin clients are low-cost, stripped-down versions of desktop computers. They do not have the storage capacity or computing power of typical desktop computers, nor do they need it for the role they play. They are used primarily in small businesses and educational institutions. Desktop computers are relatively small, inexpensive single-user computer systems that are highly versatile. They are small enough to fit on an office desk, and can provide sufficient memory and storage for most business computing tasks. Workstations are computers that are more powerful than personal computers but still small enough to fit on a desktop. They are used to support engineering and technical users who run applications requiring a high-end processor. A computer server is a computer designed for a specific task, such as network or Internet applications. Servers typically have large memory and storage capacities, along with fast and efficient communications abilities. Mainframe computers are large, powerful computers often shared by hundreds of concurrent users connected to the machine via terminals. The mainframe computer must reside in an environment-controlled computer room or data center with special heating, venting, and air-

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conditioning (HVAC) equipment to control the temperature, humidity, and dust levels around the computer. In addition, most mainframes are kept in a secured data center with limited access to the room through some kind of security system. Supercomputers are the most powerful computer systems, with the fastest processing speeds. Originally, they were primarily used by government agencies to perform the high-speed number crunching needed in weather forecasting and military applications. With the recent improvements in the cost and performance (lower cost and faster speeds) of these machines however, they are now being used more broadly for commercial purposes. Selecting and Upgrading Computer Systems Computer systems are often upgraded by installing additional memory, faster processors, more hard disk storage, or various input and output devices to support new or changing business needs. When upgrading computer systems, companies must keep hardware, main memory, and printer considerations in mind.

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Arithmetic/logic unit (ALU) - the part of the CPU that performs mathematical calculations and makes logical comparisons. Blade server - a server that houses many individual computer motherboards that include one or more processors, computer memory, computer storage, and computer network connections. Byte (B) - eight bits that together represent a single character of data. Cache memory - a type of high-speed memory that a processor can access more rapidly than main memory. Central processing unit (CPU) - the part of the computer that consists of three associated elements: the arithmetic/logic unit, the control unit, and the register areas. Clock speed - a series of electronic pulses produced at a predetermined rate that affects machine cycle time. Compact disc read-only memory (CD-ROM) - a common form of optical disc on which data, once it has been recorded, cannot be modified. Control unit - the part of the CPU that sequentially accesses program instructions, decodes them, and coordinates the flow of data in and out of the ALU, registers, primary storage, and even secondary storage and various output devices. Coprocessor - the part of the computer that speeds processing by executing specific types of instructions while the CPU works on another processing activity. Data entry - process by which human-readable data is converted into a machinereadable form. Data input - process that involves transferring machine-readable data into the system. Desktop computer - a relatively small, inexpensive, single-user computer that is highly versatile. Digital audio player - a device that can store, organize, and play digital music files.

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Digital camera - an input device used with a PC to record and store images and video in digital form. Digital video disc (DVD) - a storage medium used to store digital video or computer data. Direct access - a retrieval method in which data can be retrieved without the need to read and discard other data. Direct access storage device (DASD) - a device used for direct access of secondary storage data. Disk mirroring - a process of storing data that provides an exact copy that protects users fully in the event of data loss. Execution time (E-time) - the time it takes to execute an instruction and store the results. Flash memory - a silicon computer chip that, unlike RAM, is nonvolatile and keeps its memory when the power is shut off. Gigahertz (GHz) - billions of cycles per second. Grid computing - the use of a collection of computers, often owned by multiple individuals or organizations, to work in a coordinated manner to solve a common problem. Handheld computer - a single-user computer that provides ease of portability because of its small size. Hardware - any machinery (most of which uses digital circuits) that assists in the input, processing, storage, and output activities of an information system. Instruction time (I-time) - the time it takes to perform the fetch-instruction and decodeinstruction steps of the instruction phase. LCD displays - flat displays that use liquid crystals—organic, oil-like material placed between two polarizers—to form characters and graphic images on a backlit screen. Machine cycle - the instruction phase followed by the execution phase. Magnetic disk - a common secondary storage medium, with bits represented by magnetized areas. Magnetic stripe card - a type of card that stores limited amounts of data by modifying the magnetism of tiny iron-based particles contained in a band on the card. Magnetic tape - a secondary storage medium; Mylar film coated with iron oxide with portions of the tape magnetized to represent bits. Mainframe computer - a large, powerful computer often shared by hundreds of concurrent users connected to the machine via terminals. Massively parallel processing systems - a form of multiprocessing that speeds processing by linking hundreds or thousands of processors to operate at the same time, or in parallel, with each processor having its own bus, memory, disks, copy of the operating system, and applications. Megahertz (MHz) - millions of cycles per second. Microcode - predefined, elementary circuits and logical operations that the processor performs when it executes an instruction. MIPS - millions of instructions per second. Moore’s Law - a hypothesis that states that transistor densities on a single chip double every 18 months. MP3 - a standard format for compressing a sound sequence into a small file.

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Multicore microprocessor - a microprocessor that combines two or more independent processors into a single computer so they can share the workload and deliver a big boost in processing capacity. Multiple instruction/multiple data (MIMD) - a form of parallel computing in which the processors all execute different instructions. Multiprocessing - the simultaneous execution of two or more instructions at the same time. Network-attached storage (NAS) - storage devices that attach to a network instead of to a single computer. Optical disc - a rigid disc of plastic onto which data is recorded by special lasers that physically burn pits in the disc. Parallel computing - the simultaneous execution of the same task on multiple processors to obtain results faster. Pipelining - a form of CPU operation in which multiple execution phases are performed in a single machine cycle. Pixel - a dot of color on a photo image or a point of light on a display screen. Point-of-sale (POS) device - a terminal used in retail operations to enter sales information into the computer system. Policy-based storage management - automation of storage using previously defined policies. Portable computer - a computer small enough to be carried easily. Primary storage (main memory; memory) - the part of the computer that holds program instructions and data. Radio Frequency Identification (RFID) - a technology that employs a microchip with an antenna that broadcasts its unique identifier and location to receivers. Random access memory (RAM) - a form of memory in which instructions or data can be temporarily stored. Read-only memory (ROM) - a nonvolatile form of memory. Redundant array of independent/inexpensive disks (RAID) - method of storing data that generates extra bits of data from existing data, allowing the system to create a “reconstruction map” so that if a hard drive fails, the system can rebuild lost data. Register - a high-speed storage area in the CPU used to temporarily hold small units of program instructions and data immediately before, during, and after execution by the CPU. Scalability - the ability to increase the capability of a computer system to process more transactions in a given period by adding more, or more powerful, processors. Secondary storage (permanent storage) - devices that store larger amounts of data, instructions, and information more permanently than allowed with main memory. Sequential access - a retrieval method in which data must be accessed in the order in which it is stored. Sequential access storage device (SASD) - a device used to sequentially access secondary storage data. Server - a computer designed for a specific task, such as network or Internet applications. Single instruction/multiple data (SIMD) - a form of parallel computing in which the processors all execute the same instruction on many data values simultaneously.

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Smartphone - a phone that combines the functionality of a mobile phone, personal digital assistant, camera, Web browser, e-mail tool, and other devices into a single handheld device. Source data automation - capturing and editing data where the data is initially created and in a form that can be directly input to a computer, thus ensuring accuracy and timeliness. Speech-recognition technology - input devices that recognize human speech. Storage area network (SAN) - the technology that provides high-speed connections between data-storage devices and computers over a network. Supercomputers - the most powerful computer systems with the fastest processing speeds. Thin client - a low-cost, centrally managed computer with essential but limited capabilities and no extra drives, such as a CD or DVD drive, or expansion slots. Virtual tape - a storage device that manages less frequently needed data so that it appears to be stored entirely on tape cartridges, although some parts of it might actually be located on faster hard disks. Workstation - a more powerful personal computer that is used for technical computing, such as engineering, but still fits on a desktop.