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    Com.app.management Com.app.management Document Transcript

    • MBA – 1ST SEM NOTES M. D UNIVERSITY, ROHTAK SUBJECT: COMPUTER APPLICATION IN MANAGEMETNQ. What Is a Computer?Ans. The word computer came from the Latin word “COMPUTARE” that means tocalculate. Obviously one of the most important functions of the computer is to docalculations. Besides this, it can do many more tasks.Many definitions can be found in many books. The feasible and understandable definitionof the computer would be the following.“It is an electronic device which can perform predefined arithmetical and logical operationsin an orderly manner without any error.” OR“It s a digital device which receives input, stores it, processes it and finally gives a desiredoutput but all under the control of a set of instructions which are called programs.” INPUT PROCESIN OUTPUT G Simple Input/Output SystemQ. Functional Component of Computers?Ans: - A computer consists of three main units as given below:- 1) Input Unit 2) Central Processing Unit 3) Output Unit.A) Input UnitAn Input unit means a device to feed instructions and data to a computer. The data and theinstructions coded in an appropriate language are provided to the computer through thisunit. The user has an access to the computer through this unit only. Some of the popularinput devices are Keyboard, Mouse, Joystick, Track Ball, Punched Cards, and Light Penetc. 1
    • B) Central Processing UnitIt is a major unit, which controls all other units or parts of a computer. It further consists of: i) Center Processing Unit (CPU): The combinations of ALU and CU; of a computer is called CPU, and the CPU of a Micro-computer is called the Microprocessor. Arithmetic Logical Unit (ALU) carries out sorts of arithmetical calculations like addition subtraction, and supervises the functions of all the other unites. It works very similarly to the active part of human brain which keeps coordinating all body-movement. ii) BUS- Buses are actually lines and circuits that carry signals to and from the CPU. There are three types of buses viz: Address Bus: It originates from CPU; any access of data from the memory depends on the address sent by the CPU through these address buses. Data Bus: It carries data to and from the CPU. Unlike the address buses, these are bi-directional, carrying data both ways. Control Bus: It carries the control signals from the CPU to coordinate the other internal and external device that works with the CPU. iii) Memory Unit: The memory unit is the area where the computer stores data and instructions. There are two kinds of memories: Internal memory and External memory. Internal memory are Random Access Memory (RAM) and Read Only Memory (ROM) and External memory is a Hard Disk etc. iv) Secondary Storage Media: Since the contents in RAM are erased with the loss of electric power, it becomes necessary to store the data for future use. The programs or data can be stored into these devices permanently in the form of magnetic sports. Information stored in the devices can be processed by downloading to the computer whenever it is required. Ex. Floppy Diskette, Hard Disk, Compact Disk (CD-ROM), Magnetic Tape etc. C) Output Unit We get raw as well as processed data either in visible, audible, or printed from through this unit. It provides the communication between the computer and user. The results of various operations are communicates to the user through output devices like: Visual Display Unit(VDU), Plotters, Speech Synthesizers, Printers etc.Q. CLASFICATIONS OF COMPUTER?Ans: - On the basis of functions: Computers can be classified into three differentcategories. 1. Analog: It operates on mathematical variables that change with continuously varying physical qualities such as, electric current, pressure, temperature, time etc. Such computers are signal- problem-oriented that is specific to a particular task. Ex. Integrator, Summator etc. 2
    • Limitations of analog computers:-1 These don’t have logical facilities afforded by programming.2 Don’t have the ability to store data in large quantities.3 Cost of implementation of computation is vary high.2. Digital: It operates with the discrete signals in the form of numbers especially zeros and ones and process data using standard arithmetic operations.. Such computers are many problem oriented. Ex. IBM-PC, Apple, Macintosh, and other available in the market. Classification of digital computers:- A. Super Computers: They are the fasters and the most expensive machines, and are considered a national resource. Some of the areas in which super computers are being used are Weather forecasting, biomedical research and aircraft design. B. Mainframe Computer: Mainframes are installed in large rooms. It occupies a large amount of space due to its accompanying services such as banks of magnetic disk, magnetic taps, high-speed printers, modems sand several terminals. It can perform vary complex scientific calculations, and they are mostly used for scientific purpose. They are also used where the company has its operations in different cities or different countries, such as Banks, or Credit Card companies. More then 100 uses can work at a time same time without degrading its performance.Ex.: CYBER-76, IBM 3000, UNIVAC 1180 etc. C. Mini Computers: Physically it may be smaller, in comparison, to the Mainframe, Like the mainframe; many users can simultaneously work on them. It is used for controlling manufacturing processes. They are mainly used in Large business houses. Ex. POP 11/73, HP 300, VAX 11, PRIME etc. D. Microcomputer: We can accommodate it on a desk and only one person can use it at a time. Therefore, the term Personal Computer (PC) has been given to such computers. These are used for small business, office administration purpose and even in playing games.Ex:- IBM PC XT/AT, COMPAQ, SCER, AST, EPSON etc. 3 Hybrid: It is combination of analog and digital computers. Which uses a special devices called MODEM to convert analog signal to digital and vice versa. The full form of MODEM is Modulator and Demodulator. Information can be transferred to geographically dispersed areas through computers by use of MODEM. 3
    • Q. CHARACTERISTICS OF COMPUTERS? Ans:- SPEED-: Computers can work are extremely high speeds and much faster then human. The speed of a computer is measured in clock cycle i.e. Hertz (Hz). The time required for the computer to execute basic mathematical operations varies from a few microseconds for small machines to a few nanoseconds or even less for large ones. ACCURACY:-Speed is of no use, if the calculations made, have errors, Computers don’t make mistakesby themselves. If a computer is making a mistake then that means that there must besomething wrong with program. The computer can make mistake in situations where inputis wrong. Hence, if the input data is valid and if the program is correct and reliable, then thecomputer would produce accurate output.SOTRAGE CAPACITY:-The computer can store large amount of instructions, which are called programs, and alarge volume of data. There is no need to write the instruction again and again for a similarkind of activity. Computers have devices, which can store programs, the user just need torun them, whenever he needs. Computer can store large volumes of data for a life longperiod. The most important part is; it is most convenient to process the data and to find thedata on a computer.DILIGENCE:-Computers never get tired or bored, as in case of human beings. They never feel exhaustedby repetitive tasks. And they never take any time switching tasks.VERSATILITY:-Computers are experts in every field. They can perform various kinds of tasks. The moderncomputers can even perform more then one task same time.SECURITY:-Computers can provide security to the data. With the help of passwords we can restrictunauthorized users to see the data stored in the computer. 4
    • Q. GERATION OF COMPUTER LANGUAGES?Ans. Programming Languages are software on which application software are developed.Languages let the programmers make programs, which perform specific functions.Programmers have to use different words for making applications in different languages.Ex. A “Copy” command may be used as “cp” in one language and “copy” in other. Hence agood programming language must have the following characteristics:Easy Syntax: The words to be used should be simple and must relate to the tasks they haveto perform.Less coding: Languages must support the programmers with common programmers neednot write same codes again and again.Programming languages must provide good debugging tools so that programmers need notcompile again and again.Programs written should be easy to modify or update.Programming languages should provide all the necessary help files.Programs written must be hardware independent. Programs should run on all kinds andmake of hardware’s.First generation Language:-The first generation language was a machine language, which understood only the binarycodes i.e. 0 and1. It is also called as Binary language. But this machine language washardware dependent. Different programs were required for different hardware’s. It used tobe very tedious and complex programming.Second Generation Language:-The second-generation language was an assembly language. The codes in assemblylanguages were easy to understand, as they were no more in 0’ss and 1’s. The very purposeof these languages was to bring the man and machine very near toe each other, both usingdifferent languages but easily understood by each other.Third Generation language ( High Level Language):-It was easier to code in Assembly language as compared to Machine language. But still,there was a need of language, which understands English commands. The languagesdeveloped, which were near to English language, for the use of writing the program in 1960were known as High Level Languages. The different high-level languages, which can be 5
    • used are FIRTRAN, COBOL, BASIC, PASCAL etc. A common man, who need not learnthe actual working of a computer in assembly or binary language, can learn theselanguages.Fourth Generation language(4GLs):- The aim behind developing $ GL languages was to cut down on development steps andcoding. In a 4GL the user does not directly with the operating system through commands,rather he would interact with a utility software provided by the 4 GL, which in turn willinteract with the operating system.Q: - APPLICATION OF COMPUTER IN BUSINESS?Ans:- Chairman Board of Directors President VP VP VP VP VP Finance Production Sales Purchas HRD e Accounts Production Marketing Purchase Personal Officers Managers Managers Managers Managers EDP/MIS Stores/Materials Manager Manager 6
    • The above organizational Chart is given here to show where in the hierarchy the EDPDepartment comes in. They are basically a service department who interacts with alldepartmental heads to give them necessary processed information and should be willinglyaccountable for all data needs of the organization.We will now look at the various business applications normally computerized.1 Accounts: - Preparation of Cash Book, Bank Book, Debit Notes, Credit Notes, Invoices,Journal Book, General ledger, Sub ledgers, Trial Balance, Profit and Loss statements,Balance sheet, Cash flow analysis and other accounting statements are prepared using theAccounting System. Accounts Receivable and Payable are also incorporated in this Systemas sub systems.2.Inventory Control:- Preparation of Stock Ledger, Consumption Analysis of Itemsissued under different head of accounts, List of fast moving and slow moving items, ABCAnalysis are some of the products of this Systems. Online enquire of stock status of a givenitem can also be done together with check of expiry date, reordering status, items fallingbelow danger levels etc.3 Purchase:- Maintains a purchase order file and a Supplier Master File to keep track ofPending Purchases. Vendor Rating, processing of Quotations and placing a purchase orderis carried out by a good purchases made in a given period, item wise purchase details etc.are produced as and when necessary.4. Sales:- Apart from maintaining the sales master, sales order and other required files,order Processing, Delivery challans, Invoicing, sales returns, sales analysis re done by thisSystem. Non availability, picking List, Pending sales date of delivery wise, salesmen wiseand customers wise sales analysis, region wise sales reports are also prepared. E. Payroll:- On acquiring a new computer in an organization, normally payroll system is the one which is computerized first since the procedures and calculations are well defined even in a manual payroll system. Preparation of pay slips, coinage analysis, department wise earning and deductions, provident fund returns, Income Tax statements etc. are also the bye products of this system. F. Fixed Assets Inventory:- Monitoring of Fixed Assets, their evaluation, depreciation calculations based on different methods and preparation of the schedule of fixed assets are the main activities of this sub system. G. Budgetary Control:- Creation and maintenance of the budget master file, Reports of expenditure approved but not incurred, monthly budget control, budget and expenses for any given period, budget report budget head wise are the components of this system. 7
    • Q. OPERATING SYSTEMS?Ans. An OS is a program that acts as an intermediary between user of a computer and thecomputer hardware. The purpose of an OS is to provide an environment in which a user canexecute programs. The primary goal of an OS is thus to make the computer systemconvenient to use. A secondary goal is to use the computer hardware in an efficientmanner.Main functions of an Organization System:- 1. Process Management:- A Process is a program in execution. During execution, a process needs certain resources such as CPU time, memory space, files, and I/O devices. At a particular instance of time, a computer system normally consists of a collection of processes. The process management module of an operating system takes care of the creation and deletion of processes, scheduling of various system resources to the different processes requesting them, and providing mechanisms for synchronization and communication among processes. 2. Memory Management: To execute a program, it must be loaded, together with the data it accesses, in the main memory (at least partially). To improve CPU utilization and to provide better response time to its users, a computer system normally keeps several programs in main memory. The memory management module of an operating system takes care of the allocation and de-allocation of memory apace to the various programs in need of the resource. 3. File Management: All computer systems are used for storage, retrieval and sharing of information. A computer normally stores such information in units called files. Processes can read information from files and can create new files for storing newly information. Information stored in files is made persistent by storing them on a secondary storage media such as a magnetic disk. Files provide a natural and easy means of information sharing. That is, a file can be created by one application and then shared with different applications at a later time. The file management module of an o/s takes care of file-related activities such as organization, storing, retrieval, naming, sharing, and protection of files. It allows programs to use a set of operation that characterize the file abstraction and free the programmers from concerns about the details of space allocation and payout of the secondary storage device. 4. Devices Management: A computer system normally consists of several I/O devices as terminal, printer, disk, and tape. The device management module of an operating system takes care of controlling all the computer’s I/O devices. It keeps track of I/O request from processes, issues commands to the I/O devices, and ensures correct data transmission to/from an I/O device. It also provides an interface between the devices and the rest of the system that is simple and easy to use. Often, this 8
    • interface is device independent, that is, the interface is same for all types of I/O devices. 5. Security: Computer system often stores a large amount of information, some of which is highly sensitive and valuable to their users. Users can trust the system and r4ly on it only if the various resources and information of a computer system are protected against destruction and unauthorized access. The security modules of an operating system ensure this. This modules also ensures that when several disjoint processes are being execute same time; one process does not interface with the others, or with the operating system itself. 6. Command Interpretation: A user communicates with the operating system, for using the various system resources, via a set of commands provided by the operating system. The operating system also provides a simple language, known as command language(CL) or job control language(JCL), using which a user can put several commands together from the command set to describe the resource requirements of the job. The command interpretation module of an operating system takes care of interpreting user commands, supplied individually or in the form of command language, and directing the system resources to handle the requests. With this mode of interaction with the system, the user is usually not too concerned with the hardware details of the system, or with hoe the operating system will direct the hardware to handle certain requests.UNIT-IINETWORKSNetworks are an inter connection of computers. These computers can be linked togetherusing a wide variety of different cabling types, and for a wide variety of different purpose.The basis reasons why computers are networked are- 1. To share resources (files, printers, modems) 2. To share the same data (Airways or Railways ticketing) 3. To share application software’s such as Databases etc. 4. Increase productivity. 5. Data security, if all the data is placed at one place, it can be efficiently secured.Components of Networking-There are three main components of networking namely A sender, A receiver and thecommunication channel which connects them. The data send by the computer is in Digitalsignals, but the communication channel that is the telephone line, carries analog signal.Hence we need devices, which can convert these signals. Such a device is called a modem.Tacking an example of communication through computers: 1. Sender computer: The sender of the message will give instruction to the sender computer to transmit data to the receivers address. Now the computer will transmit the data in digital signals. 9
    • 2. Sender modem: Communication cables work on analog signals, hence the modem on the sender’s end converts the digitals signals into analog signals and transmits the data. In case the communication is with computers placed near by, they can be connected by a simple networking cable called a LAN cable. In that case a modem is not required because these cables can transmit data in digital signals. 3. Communication Channels: If communication can to be done with a computer placed far away, then the most common communication channels used these days are telephone lines. Telephones lines carry the information in analog format from one place to another. If the distance between two computers is vast, then satellites are also used. 4. Receiver’s Modem: A modem is also required at the Receiver’s end, to convert the analog signals into digital signals, which can be understood by the Receiver’s computer. 5. Receiver’s computer: Receiver also requires a computer to read the message received. The receiver can view the message and reply to message immediately. In that case the receiver’s computer and modem acts as sender’s computers and modem, and the cycle repeats. Hence same modem and same computer can be used for sending and as well as receiving.Q. Digital and analog Signals?Ans. Data is propagated from one point to another by means of electrical signals, whichmay be in digital or analog form. In analog signal, the transmitted power varies over acontinuous range, for ex. Sound, light and radio waves. The amplitude (v) of analog signalsis measured in volts and its frequency (f) in hertz (Hz). The higher is the frequency of thesignal, the more number of times it crosses the time axis. However, a digital signal is asequence of voltage pulses represented in binary form. Voltage +∨ 0 1/f 2/f T -∨ (a) Analog signal 10
    • 0 0 0 0 t (b) Digital signalComputer generated data is digital whereas the telephone lines used for datacommunication in computer networks are usually meant for carrying analog signals. Whendigital data is to be sent over an analog facility, the digital signals must be converted toanalog form. The technique by which a digital signal is converted to its analog form isknown as modulation. The reverse process, that is the conversion of analog signal to itsdigital form, at a destination device, is called demodulation.Q. Bandwidth?Ans. A term used to describe the data-handling capacity of a communication system isbandwidth. Bandwidth is the range of frequencies that is available for transmission of data.A narrow range of frequencies in a communication system is analogous to a narrow road.The flow of information in such a system- its data transfer rate-is limited just as is the flowof traffic in a narrow road. Wider bandwidths permit more rapid information flow. Thus,the wider the bandwidth of a communication system, the more data it can transmit in agiven period of time.When dealing with computer input/output devices, we think in terms of character persecond. The ASCII code uses 7 data bits per character plus a parity bit. For datacommunication additional bits are added to control the process. Although the number ofbits dependent upon the communication system used, commonly encountered systems use atotal of either 10 or 11 bits per character. Hence a terminal having a speed of 30 charactersper second would probably be used with a communication system, which transmits at therate of 300 bits per second.The communication data transfer rate is measured in a unit called baud. In general usage,baud is identical to bits per second. For instance, a rate of 300 baud of 300 baud is 300 bitsper second. Therefore, the 300 characters per second terminal would be said to operate at300 baud.Depending on their transmission speeds, communication channels (path) are grouped intothree basic categories:-Narrowband:- 11
    • Narrowband or sub voice grade channels range in speed from 45 to 300 bund. They areused for handling low data volumes and are adequate for low-speed devices. They are usedmainly for telegraph lines and low speed terminals.Voice-band:-Voice-band channels handle moderate data volumes and can transmit data at speeds up to9600 baud. They are so called because their major application is so for ordinary telephonevoice communication. They are also used for data transmission from slow I/O devices toCPU or form CPU to slow I/O devices. Moreover, most remote terminals are connected tocomputers through voice-band channels.Broadband:-Broadband or wideband-channels are used when large volumes of data are to be transmittedat high speed. These systems provide data transmission rates if 1 million baud or more. Acompany might use a broadband facility for high-speed computer-speed computer -to-computer communication or for same time transmission of data to several different devices.Q. NETWORK TOPOLOGIES?Ans. A network is a logical extension of a data communication system. In a computernetwork, two or more computers are linked together with carriers and data communicationdevices for the purpose of communicating data and sharing resources. The term networktopology refers to the way in which the nodes of a network are linked together. Itdetermines the data paths that may be used between any pair of nodes in the network.Although the number of possible network topologies is seemingly limitless, the four majorones are the star network, the ring network, the completely connected network, and themulti-access bus network.The choice of network topology for installing network depends upon a combination offactors such as:- 1. The desired performance of the system. 2. The desired reliability of the entire system. 3. Size of the system. 4. Expandability of the system. 5. Cost of the components and devices required to implement the network. 6. Delays involved in routing information from one node to another.STAR NETWORK:-In the star networking, multiple computers are connected to a host computer. That is, thecomputers in the network are not linked directly to each other and can communicate onlyvia the host computer. The routing function is performed by the host computer, which 12
    • centrally controls communication between any two other computers by establishing alogical path between them. HOST COMPUTER ADVANTAGES:- 1. Star topology has minimal line cost because only n-1 lines are required for connecting n nodes. 2. Transmission delays between two nodes do not increase by adding new nodes to the network because any two nodes may be connected via two links only. 3. If any of the local computes fails, the remaining, the portion of the network is unaffected.DISADVANTAGE:- 1. The system crucially depends on the central node. If the host computer fails, the entire network fails.RING NETWORK:-In this topology each computer in the network has communicating subordinates, but withinthe ring there is no master computer for controlling other computers. A node receives datafrom one of its two adjacent nodes. The only decision a node has to take is whether the datais for its own use or not. If it is addressed to it, it utilizes it. Otherwise, it merely passes iton to the next node.ADVANTAGES:- 13
    • 1. The ring network works well where there is no central-site computer system. 2. It is more reliable then a star networks because communication is not dependent on a single host computer. If a link between any two computers breaks down, or if one of the computers breaks down, alternate routing is possible.DISADVANTAGES:- 1. In a ring network, communication delay is delay is directly proportional to the number of nodes in the network. Hence addition of new nodes in the network increases the communication delay. 2. The ring network requires more complicated control software then star networkCOMPLETELY CONNCTED NETWORK:-A completely connected network has a separate physical link for connecting each node toany other node. Thus each computer of such a network has a direct dedicated link, called apoint-to-point link, with all other computers in the network. The control is distributed witheach computer deciding its communication priorities.ADVANTAGES:- 14
    • 1. This type of network is very reliable, as any link breakdown will affect only communication between the connected computers. 2. Each node of the network need not have individual routing capability. 3. Communication is very fast between any two nodes.DISADVANTAGE:-1. It is the most expensive network from the point of view of link cost. If there are nodes inthe network, then n (n-1)/2links are required. Thus, the cost of linking the system growswith the square of the number of nodes.MULTI ACCESS BUS NETWORK:- Computers Single communication line shared by all nodesIn multi-access bus networking, a single transmission medium is shared by all nodes, Thatis, all the computers are attached to the same communication line. When a particularcomputer wants to send a message to another computer, it appends the destination addressto the message and checks whether the communication line is free. As soon as the linebecomes free, it broadcasts the message on the line. As the message travels on the line,each computer checks whether it is addressed to it. The message is picked up by theaddressee computers, which sends an acknowledgement to the source computer and freesthe line. This type of network is also known as ‘multipoint’ or’ broadcasting’ network. It isappropriate for use in a local area network where a high-speed communication channel isused and computers are confined to a small area. It is also appropriate when satellitecommunication is used as many computers at a number of geographical locations mayshare one satellite channel.ADAVANTAGES:- 15
    • 1. The main advantage of a multi-access bus network is reduction in physical lines. 2. The failure of a computer in the network does not affect the network functioning for other computers. 3. Addition of new computers to the network is easy.DISADVANTAGES:- 1. All computers in the network must have good communication and decision-making capability. 2. If the communication line fails, the entire system breaks down.HYBRID NETWORK:-Different network configurations have their own advantages and limitations. Hence inreality a pure star or ring or completely connected network is rarely used. Instead, anorganization will use some sort of hybrid network, which is a combination of two or moredifferent network topologies. The exact configuration of the network depends on the needsand the overall organization structure of the company involved. In some cases, the hybridnetwork may components of star, ring, and completely connected networks. A typicalhybrid network of this type is shown in the following figure.Q. PACKET TRANSMISSION?Ans. A message is a logical unit of information and can be of any length. In packettransmission a message is split up to ‘packets’ of a fixed size (of the order of one or fewthousand bits). Besides the block of data (part of a message) to be sent, a packet has aheader that contains the destination and source addresses, control information, messagenumber, number of current and last packet, synchronization bits, acknowledgement anderror checking bytes, etc. Like message switching the packets may be routed from thesender node to the destination node either by store-and-forward method or by broadcastmethod. In the store and forward method, the packets are stored temporarily at the 16
    • intermediate nodes for error recovery purchases and are routed to the next node based on anavailable free channel. The actual path taken by the packet to its destination is dynamic asthe path is established as its travels along. Thus, it s possible that different packets of thesame message can be routed across different paths leading to the same destination uponline availability and congestion.ADVANTAGES:- 1. Unlike messages, packets are of small and fixed size. Hence the storage requirement for buffering the packets at intermediate nodes is minimal. 2. Since the routing is done on packet basis the intermediate nodes do not have to wait for the either message, hence the transmission is very fast. 3. The method is fast enough for interactive/real time applications. 4. It is most suitable for ‘bur sty’ computer-to-computer communication and is widely used in wide area networks.DISADVANTAGES:- 1. Due tot the need to buffer each packet at every intermediate node and to reassemble the packets at the destination node, the overhead incurred per packet is large. 2. There is no guarantee of how long it takes a message to go from its source node to its destination node because the time taken for each packet depends on the route chosen for that packet, along with the volume of data being transferred that route.Q. LONG DISTANCE COMMUNICATION?Ans. If data is sent over long distance s, the analog signal can become weak and distorted.To avoid this, amplifiers are used. An amplifier used in a communication system is similarto the amplifier used in a home stereo system-it strengthens or amplifies a weak signal.Amplifiers are typically placed alone communication lines between modems.Today, signals are also sent in digital mode. In this case modems are not neede. Whendigital mode of transmission is used over long distances, a repeater is used to receive andthen transmit the signal. Like an amplifier, the purpose of a repeater is to strengthen a weakdigital signal over long distance.Digital transmission of digital data is preferred to analog transmission of digital data due tothe following reasons:- 1. Lower cost. 2. No modems required. 3. Higher transmission speed possible, and 4. Lower error rate. 17
    • Q. APPLICATIONS OF NETWORK?Ans. Communication-Using a computer connected to the Internet, there are a variety of ways for people tocommunicate with one another. People have an insatiable desire to communicate (letters,postcards, telegram, radio, TV, telephone, answering machine, fax, etc.). A computerconnected to the Internet offers several more options.ELECTRONIC MAIL- 1. Like a postcard or letter. 2. Several technical differences.  Sender writes on his or her computer and recipient receives message on a different computer.  Usually mail is delivered more quickly then postal mail.  The same message can be sent one or more people. 3. Several cultural differences.  E-mail messages can be very short.  Often a dialog between two or more people.  Can quote previous message. 4. Cheapest source of communication.  E-mail messages can be send any where in the world at same price.  Unlike Fax, you don’t have to wait for the receiver to receive the message.  There are various sits offering free email services such as www.yahoo.com or www.hotmail.com.Browsing:-The Internet good at storing large amounts of data allows individuals to browse richelycross-references texts and follow trails of interconnected information as one does in enencyclopendia-1. The heart of the Internet is browsing.  We find a lot of cross- referenced text; hence it is easy to shift between pages.  Browsing is accomplished by following links, the connections between related information. 2.A number of different Internet facilities allows browsing including the Web, gopher, and wais. 3. You need Internet browser programs on your computer to browser on Internet such as Netscape Navigator, Microsoft Internet Explorer etc. 4. We find material on all areas such as Research, Education, Health, Business, Stock etc. 18
    • WORLD WIDE WEB:-1.The web is a random collection of information written and cross-referenced by themasses.a) Information is stored on computers around the world that are connected to the Internet.2.Browsers are software products that provide a means of viewing the information on theWeb. 3. A web site is a collection of related pages. 4. A home page is a starting point for browsing a web site. 5. A URL is the electronic equivalent of a call number on the spine of a library book. It indicates the location of a page on the web.SEARCHING:-With so much information, it’s hard to find specific information by browsing. The Internetcontains indexes and other tools to help people search. These are called search engines.INTEGRATING:-Materials on the Internet can be integrated into teaching, learning and professionalactivities. Students can research almost any from A-Z. Teachers can design lessons basedon material published on the Internet.CREATING:-People can make their own websites to share the data with the rest of the world. Companiescan make their corporate sites to market themselves on Internet, Scientists can put theirresearch work, teachers can put lessons, writers can put their articles etc.Q. DATABASE?Ans. Databases and database technology are having a major impact on the growing use ofcomputers. It is fair to say that databases play a critical role in almost all areas wherecomputer are used, including business, engineering, medicine, law, education, and libraryto name a few .A database is a collection of related data. By data we mean known facts that can berecorded and that have implicit meaning. For Ex. Consider the names, telephone numbers,and addresses of the people you know. You may have recorded this data in an indexedaddress book, or you may have stored it on a diskettes, using a personal computer andsoftware such as DBASE IV or V, Microsoft ACCESS, or EXCEL. This is a collection ofrelated data with an implicit meaning and hence is a database.A database has the following properties:- 19
    • 1. A database represents some aspect of the real world, sometimes called the mini- world or the Universe of Discourse (UoD). Changes to the min-world are reflected in the database. 2. A database is a logically coherent collection of data with some natural meaning. 3. A database is designed, built, and populated with data for a specific purpose. It has an intended group of uses and some preconceived applications in which these users are interested. 1. The data in the database is stored in the table format. S.no. Emp. Code Emp.Name Address Field Name 1 05 ABC 56/6, Fbd Data item 2 06 XYZ 96/8, Fbd File S.no-1, emp.Code-05, Emp.Name-ABC and Address 56/6,fbd is called a record. Field Name-: The name of each data item is known as field name e.g Address, Emp. Name etc. Record:- Record is a collection of related data Data Item:- Data item or field is a set of character. When Not to Use a DBMS- 1. High initial investment in hardware, software, and training. 2. Generally that a DBMS provides for defining data. 3. Overhead for providing security, recovery, and integrity functions.DATABASE OBJECTIVES:- 1. Compactness-: If we use database, then all records are stored in computer and only one place (on e file). So we have no need for paper files. 2. The data can be shared:- Sharing means not only that existing applications can share the data in the database, but also that new applications can be developed to operate against that same data. In other words, it might possible to satisfy the data requirements of new applications without having to add any new data to the database. 20
    • 3. Redundancy can be reduced:- In non database system each application has its own private files. This fact can often lead to considerable redundancy in stored data, with resultant waste in storage space. For example, a personnel application and an education records application might both own a file that includes department information for employees. But if we maintain all files in a database then data administrator allows only few members to make changes in the files, he also aware about this. His database should be aware of it, if it exists, and should assume responsibility for “ propagating updates”. 4. Inconsistency can be avoided:- This is really a corollary of the previous point. Suppose a given fact about the real world-say the fact that employee E3 works in department D8- is represented by two distinct entries in the database. Suppose also that the DBMS is not aware of this duplication. Then there will necessarily be occasions on which the two entries will not agree. Namely, when one of the two has been update and the other not. At such times the database is said to be inconsistent. Cleary, a database that is in an inconsistent state is capable of supplying incorrect or contradictory information to its users. Of course, if the given fact is represented by a single entry (i.e. if the redundancy is not removed but is controlled (by making it known to the DBMS), then the DBMS can guarantee that the database is never inconsistent as seen by the user, by ensuring that any change made to either of the two entries is automatically applied to the other one as well. This process is known as propagating updates. 5. Transaction Support can be provided:- A transaction is a logical unit of work, typically involving several database operations (in particular, several update operations). The standard example involve the transfer of a cash amount from one account A to another account B. Cleary two updates are account B. If the user has stated that the two updates are part of the same transaction, then the system can effectively guarantee that either both of them are done or either is- even if, e.g. the system fails (say because of a power outage) halfway through the process. 6. Integrity can be maintained:- The problem of integrity is the problem of ensuring that the data in the database is correct. Inconsistency between two entries that purpose to represent the same “fact” is an example of lack of integrity, of course, this particular problem can arise only if redundancy exists in the stored data. Even if there is no redundancy the database might still contain incorrect information. Centralized control of the database can help in avoiding such problems- insofar as permitting the data administrator to define, and the DBA to implement can avoid them. 7. Easy to access :- DBMS allows convenient and efficient retrieval of data. But in a conventional file processing system, any retrieval request can be served until the programmer has designed its application program. Thus, DBMS provides a more responsive data retrieval system.ENTITIES:- 21
    • A record that can be uniquely identified is called an entity. Entity is an object that exits andis differ, from all other objects, e.g. a student Sahil with roll no, “2254” is an entity. Eachentity has some set of properties.ATTRIBUTS:-Attributes are the properties or characteristics of an entity e.g. an entity of entity set‘student’ may have attributes- Sname, Rollno, trade and semester. The values of theseattributes identify one entity from others.SCHEMA:-Database schema refers to the design of the database. Schema is of a part of the database.Schema is a logical database description and is drawn as a chart of the types of data that areused. It gives the names of the entities and attributes and specifies the relationships (one-to-one, one-to-many, many-to-many) between them. I t is a framework into which the valuesof the data items can be fitted. The schema will remain same if time to time value changes.SUBSCHEMA-The term sub schema refers to the same view, but for the data-item types and record typeswhich a particular user uses in a particular application. Therefore, many different sub-schemas can be derived from one schema.UNIT-IVInternetworking:-Ans.Interconnecting of two or more networks to form a single network is calledinternetworking, and the resulting network is called an inter-network. Therefore, a WANof multiple LAN’s is an inter-network.Inter-networks are often heterogeneous network composed of several network segmentsthat any differ in topology and protocol. For example, an inter-network may have multipleLAN’s some of which may have multi-access bus topology while others may have ringtopology; some of these LAN’s may be using Ethernet technology while others may beusing Token Ring technology; and some segments of the network may be using the IP suitewhile others may be using IBM’s SNA (System Network Architecture) protocol suite.Inter-networking allows these relatively unrelated networks to evolve into a single workingsystem. That is, the goal of inter-networking is to hide the details of different physicalnetworks, so that the resulting inter-network functions as a single coordinated unit.Internetworking two networks having the same topology and protocol is because the twonetworks an easily communicate with each other. Internetworking two dissimilar networksthat have different topologies and protocols requires an inter-networking scheme that 22
    • provides some common point of reference for the two networks to communicate with eachother. That point of reference might be a high-level protocol common to the two networks,a device that allows inter-connection of different topologies with different physical andelectrical characteristics, or a protocol that allows operating environment differences to beignored. The most commonly used approach is to make use of common high-levelprotocols for moving data between common layers on a communications model such as theOSI or the IP suits. Inter-networking tools, such as bridges, routers, brouters, and gateways,make extensive use of this approach.INTERNET PROTOCOL ADDRESS:-Ans.An Internet (IP) address is a numeric identifier assigned to each machine on an IP network.It designates the location of the device it is assigned to on the network. An IP address ismade up of 32 bitts of information. These bits are divided into four sections containing onebyte (8 bits each). These sections are referred to as octets. There are three methods fordepicting an IP address. 1. Dotted-decimal as in 130.57.30.56 2. Binary, as in 10000010.00111001.0011110.00111000 3. Hexadecimal, as in 8239 IE 38.All the tree examples given above represent the same IP address. The 32-bit IP addressingis a two-level hierarchical addressing scheme. The first part is designed as network addressand the other part of the address is designed as a node address. The network addressuniquely identifies each network. Every machine on the same network shares that networkaddress as a part of its IP address. In the IP address 130.57.30.56, of our example, the130.57 is the network address.The node address is assigned to, and uniquely identifies, each machine on the network.This part of the address must be unique because it identifies a particular machine-anindividual, as opposed to a network, which is a group. The number can also be referred toas a host address. In the sample IP address 130.57.30.56, the 30.56 is the node address.(AN IP ADDRESS IS A SOFTWARE ADDRESS, NOT A HARDWARE ADDRESS,WHICH IS A HARD-CODE IN THE MACHINE OR NETWORK INTERFACECARD.)INTERNET APPLICATIONS:-Ans. 1. To exchange electronic mail with friends all over the globe for a very small price. 2. To participate in-group discussion on topics of interest, through public news groups. 23
    • 3. To find educational tools, universities around the world, bookstores, and libraries are sharing online information. 4. Commercial electronic storefronts are growing in number in the USA and Europe. One can order different products over the Internet. 5. In the case of business one can get technical support for products one is using. One can publish information such as technical or marketing literature. 6. Because the Internet is electronic, one can make changes to reflect late breaking news that would be impossible for printed publications. Change becomes easier, updates are simpler and information is instant. 7. The Internet has become the first global venue for publishing information. This network has enough users now and it is benefiting from the positive feedback loop; the more users it gets, the more control it gets; and the more content it gets, the more users it gets. WWW PAGES AND BROWSING?Ans.The World Wide Web, or “the Web”, is an Internet based global information system thatmakes available multimedia information from over 4 million computers around the world.The Web offers video, interactive multimedia and lives audio, in addition to more basicdata types, such as text documents and still photographs.WWW is a huge collection of hypertext pages on the Internet. The concept of WWW wasdeveloped in Switzerland at the European Particle Research Centre (CERN) in the year1989.Features of WWW:-The Web is one of the most flexible and exciting tools for surfing the Internet. UsingMosaic viewer, the WWW made it possible for a site to set up a number of pages ofinformation containing text, picture, sound and even video with embedded links to otherpages. By clinking on a link, the user is moved to the page pointed to by that link. ForExample, a company can have a home page with entries pointing to other pages for productinformation, price lists, sales, technical support, communication with employees,stockholder information and so on.WWW Browsers:-A Web browser is a program you use to view pages on and navigate the World Wide Web.Browsers are sometimes referred to as Web clients or other fancy names (Internetnavigation tools”), but Web browser is the most common term.A wide range of Web browsers is available for every type of systems you can imagine,including graphical-user-interface., and the text-only for dial-up UNIX connections. Most 24
    • browsers are freeware. Usually, all you have to do is to get a browser-downloaded form theInternet. For example, Internet Explorer 5.0 version comes free as part of Window 98.Popular Web-Browsers are- 1. ncSA Mosaic 2. Netscape Navigator 3. Lynx 4. Microsoft Internet Explorer.A web Browser does the following two types of services- 1. Given a URL address, it should be able to access that information. For hypertext Web documents, this means that browser must be able to communicate with the Web server using the HTTP protocol. 2. Because the Web can also manage information contained on FTP and Gopher servers, in Usenet news communicate with those servers or protocols as well.Different browsers may format and display the same file differently, depending on thecapabilities of the hardware and the default layout options for the browser itself.SECURITY OF THE INTERNET:-Ans.Overview of internet security threats :- 1. Identity Interception:- The identity of one or more of the users involved in a communication is observed for misuse. 2. Pretending:- The pretence by a user to be a different user in order to gain access to information or to acquire additional privileges. 3. Reply:- The recording and subsequent replay of a communication at some later date. 4. Data interception:- The observation of user data during a communication by an unauthorized user. 5. Manipulation:- The replacement, insertion, deletion of user data during a communication by an unauthorized user. 6. Rejection:- The denial by the a user of having participated in part or all of a communication.FIREWALLS:- Every time a corporation connects its internal computer network or LAN to the Internet, itfaces potential danger regarding security. Due to the Internet’s openness, every corporatenetwork connected to it is vulnerable to attack. Crackers on the Internet could theoreticallybreaks into the corporate network and do harm in a number of the following ways:- 1. They could steal or damage important data. 2. Damage individual computer or the entire network. 25
    • 3. Use the corporate computer’s resources or use the corporate network and resources as a way of posing as a corporate employee. The solution for all these problems and many more is to build ‘firewalls’ to protect its network. These firewalls allow anyone on the corporate network to access the Internet bur they stop crackers, hackers or others on the Internet from gaining access to the corporate network and causing damage.(Firewalls are hardware and software combinations that are built using routers,servers and a variety of software. They sit at the most vulnerable point between acorporate network and the Internet and they can be as simple or complex as systemadministrators want to build them.) Benefits of Using a Firewall:- 1. Protection from services that are inherently more prone to attacks. 2. Access to host in the network can be strictly controlled. 3. Security is concentrated on a single firewall system. This leads to better implementation of authentication procedures. 4. Logging and statistics of network use and misuse. 5. Policy enforcement.Types of firewalls:- 1. Packet filtering. 2. Application gateways.A firewall basically performs two important functions:- 1. Gate-keeping:- Firewall acts as a gatekeeper between the company’s internal network and the outside network. It examines the location from which the data enters your system and then decides, based on your instructions, whether or not to allow that information. 2. Monitoring by Firewall:- in addition to Gate-keeping , the firewall also monitorsinformation. Monitoring is one of the most important aspects of firewall design.Monitoring functions include logging of all system activities and generation of reports forsystem administration. Monitoring can be active or passive. In active monitoring, afirewall notifies a manager whenever an incident occurs. The firewall product, Smart wall,alerts the administrator via e-mail or pager about suspicious on line activity. In passivemonitoring, a firewall logs a record of each incident in a file or a disk. Then a manager cananalyze the log periodically to determine whether attempts to access the organization haveincreased over time.E-COMMERCE:- 26
    • E-commerce is any form of business exchange or transaction in which the parties interactelectronically. Firms such as Dell (computers), Varsity-books (textbooks) and PC Flowersand Gifts are engaged in e-commerce transactions.Advantages:-Convenience:- Cyber-stores never close their doors. In a recent survey conducted byForrester Research, active Web shoppers rated convenience the number one reason to shopon-line.Savings:- Businesses such as Dell Computer Corporations and General Electric are usingthe Internet to link directly to suppliers, factories, distributors, and customers. They arewringing waste out of the system and passing on saving to customers. On-line retailers suchas Amazon.com reap the advantage of negative operating cycle: Anazon receives cash fromcredit-card companies just a day after customers place an order. Then it can hold on to themoney for 46 days until pays suppliers, the book distributors and publishers. Customersstand to benefit most of all, because they can scour the Web to search for the lowest price.There are even sits such as Compare.Net, which offers a free on-line buyer’s guide thatallows users to compare features of 10,000 products.Selection: The World’s the limit for the Web. Unrestrained by physical boundaries, cyber-stores can offer an almost unlimited selection. Go to the CD-Now and Virtual Vineyardssites and then compare the selection with the offerings of the local music or liquor store.Collapsed geographic boundaries also open up market all over the world and make upstartsindistinguishable from established companies.Personalization:- With the help of computer’s slice and dice information captured on theWeb, businesses can personalize their sales pitches and even their products. CNN’s Website enables individuals to create personal profiles of their news interests and updates themevery 15 minutes.Information:- Although it’s true that the human interface is missing, the Web makes upfor it tenfold with the amount of information available. Good sites provide moreinformation in more useful forms then the most solicitous salesclerk does.Application of E-commerce:-1.Save transaction costs for both buyers and suppliers:- A Web-powered purchasingprogram eliminates the paper chase associated with traditional requisition and orderingprocedures. At National Semiconductor, the $75 to $250 cost of processing each paper-based requisition has been cut to just $3 per electronic order.2.Reduce time between order and delivery:- Time saving are particularly dramatic forcompanies with many overseas suppliers. Adaptec Inc., a leading supplier of computerstorage, used an extranet to tie all of its Taiwanes chip suppliers together in a kind ofvirtual keiretsu. Now messages from Adaptec flow in seconds from its headquarters to itsAsian partners and adaptec has reduced the time between the order and delivery of its chipsfrom as long as 16week to just 55 days-the same turnaround time for companies that buildtheir own chips. 27
    • Consolidate purchasing systems:- One key motivation for on-line purchasing has been adesire to get rid of redundancy.3.Cut jobs for millions of clerks and order processors:- All these saving and efficienciesdon’t come without a price. National Semiconductor reduced its purchasing staff by morethen half when it took its purchasing activities on-line. On the other hand, for manypurchasing professionals, going on-line means reducing drudgery and paperwork andspending more time managing inventory and working creatively with suppliers.4. More intimate (close) relationships between partners and buyers:- Robert MondaviCorporation puts satellite images of its vineyards out over the extranet so that itsindependent growers can pinpoint potential vineyard problems and improve the grapesMondavi purchase from them.5.Level the playing field between large and small suppliers:- By using the internet’stechnology to establish secure, standing information links between companies, extranetshave helped firms do business with smaller suppliers. Currently most large manufacturersuse electronic data interchange (EDI) to order suppliers, because it provides a secure meansof coding and exchanging standardized business forms. Moving business-to-businesscommerce onto the Web also levels the playing field between local and foreign suppliersbecause purchases can source materials from suppliers all over the globe for no additionaltransaction cost.6.Create potential security disasters:- More then 80 percent of companies say security isthe leading barrier to expanding electronic links with customers and partners. Although e-mail and home banking transactions can be protected through basic encryption, the secureenvironment that businesses need to carry out many confidential interactions still does notexist. Companies are creating their own defensive strategies for keeping hackers at bay.The companies go further by sending its own security engineers to examine a partner’sdefenses and hold the partner liable for any security breach that originates from itscomputer. 28
    • Basic computer organizationEven through the size, shape, performance, reliability, and costs of computers have beenchanging over the year; the basic logical structure (based on stored program concept) as byVon Neumann has not changed. No matter what shape and size of computer we are talkingabout all computer systems perform the following five basic operations for converting rawinput data into information useful to their users: 1. Inputting. The process of entering data and instructions into the computer system. 2. Storing. Saving data and instructions so that they are available for initial or for additional processing as and when required. 3. Processing. Performing arithmetic operations (add, subtract, multiply, divide, etc) or logical operations (comparisons like equal to, less then, greater than, etc) on data in order to convert them into useful information. 4. Output. The process of producing useful information or results for the user, such as a printed report or visual display. 5. Controlling. Directing the manner and sequence in which all of the above operations are performed. The goal of this chapter is to familiarize you with computer system unites that performs these functions. This chapter will provide you with overview computer systems as computer system architects view them. The internal architectural design of computers offers from one system model to another. However, the basic organization remains same for all computer system. A block diagram of the basic computer organization is. In the figure, the solid lines are used to indicate the flow of instructions and data, and the dotted lines represent the control exercised by the control unit. It displays the five major building blocks, functional units of a digital computer system. The five units correspond to the five basic operations performed by all computer systems. The function of each these units are described below. 29
    • Program information Secondary (Result)And Data Storage Output Input Unit Primary Storage Control Unit Indicates Flow of Instructions And Data Indicates The control Arithmetic Exercised by the Logic Unit Control unit. ControlProcessing Unit (CPU) 30
    • INPUT UNIT:Data and instructions must enter the computer system before any computation can beperformed on the supplied data.The input unit that links the external environment with the computer system performs thetask. Data can entered in the computer through Keyboard or Scanner (it is a type of inputdevice). The data or instructions are accepted in the computer in binary codes, units calledInput Interfaces accomplish this transformation.In short, the following functions are performed by an input unit: 1. It accepts (or reads) the list of instructions and the data from the outside world. 2. It converts these instructions and data in computer acceptable form. 3. It supplies the converted instructions and data to the computer system for further processing.OUTPUT UNIT:The job of an out put unit is just the reverse of that of an input unit. It supplies the information as a result of data processing to the outside world. As computer works in the binary code, the results produced are also in the binary form. Hence, before supplying the result to the outside world, it must be converted in the human acceptable (readable) form. This task is accomplished by units called output Interfaces.In short the output unit performs the following functions: 1. Ist accepts the result produced by the computer, which are in the coded form and hence cannot be easily understood by us. 2. It converts these coded to the human acceptable (readable) form. 3. It supplies the converted results to the outside world. STORAGE UNIT: The data and instructions that are entered into the computer system through input units have to be stored inside the computer before the actual processing starts. This unit provides space for storing data and instructions, space for intermediate results. In short, the specific functions of storage unit are to hold (store): 1. All data to be processed and the instructions required for processing (received from input device). 2. Intermediate results for processing. 3. Final result of processing before these results are released to an output device.The storage unit of all is comprised by the following too type of storage: 31
    • 1. Primary storage. The primary storage, also known as main memory, is used to hold peaces of program instruction and data, intermediate result of the processing of the job(s)that the computer system is currently working on. These peaces of the information are represented electronically in the main memory chip’s circuitry, and while it remains in the main memory, the central processing unit can access it directly at a fast speed. The primary storage has a limited storage capacity because it is very expensive. The primary of a modern computer system is made of semiconductors device. 2. Secondary Storage. The secondary storage, also known as auxiliary storage, is used to take care of the limitations of the primary storage. That is, it is used to supplement the limit storage capacity and the volatile characteristic of a primary storage. This is a because secondary is much cheaper then primary storage and it can retain information even when the computersystem is switched off or reset. The secondary storage is normally used to hold the programinstruction, data and information of those jobs on which the computer system is notworking on currently , but needs to hold them for processing at a later time. The mostcommonly used secondary storage medium is the magnetic disk. ARITHMATIC LOGIC UNIT: The arithmetic logic unit (ALU) of the computer system is the place where the actualexecution of the of the instruction tasks place during the processing. To be more precise,calculations are performed and all comparisons are made in the ALU. The data andinstructions, stored in the primary storage prior to processing are transferred as and whenneeded to the ALU where processing takes place. No processing is done in the primarystorage unit. Intermediate results generated in the ALU are temporarily transferred back tothe primary storage until needed at a later time. Data may thus move from storage to ALUand back again to storage many times before the processing is over. After the completion ofprocessing the final result which r stored in the storage unit r released to an output device. The type and number of arithmetic and logic operations that a computer can perform isdetermined by the engineering design of the ALU. However, almost all ALU’ s aredesigned to perform the four basic arithmetic operation (add, subtract, multiply, anddivide), and logic operations or comparisons such as less than, equal to, and greater than.CONTROL UNIT:-How does the input device know that it is time for it to feed data into the storage unit? Howdoes the ALU know what should be done with the data once they are received? And how itis that only the final results are sent to the output device and not the intermediate results?All this is possible because of the control unit of the computer system. By selecting,interpreting, and seeing to the execution of the program instructions, the control unit is ableto maintain order and direct the operation of the entire system. Although, it does notperform any actual processing on the data, the control unit acts as a central nervous system 32
    • for the other component of the computer system. . It obtains instructions from the programstored in the memory, iterates the instructions, and issues signals that cause other units ofthe system to execute them.CENTRAL PROCESSING UNIT: The control unit and the arithmetic logic unit of the computer system is jointly is known ascentral processing unit(CPU). The CPU is the brain of any computer system. In a human body, the brain takes allmajor decision and the other parts of the body function as directed by the brain. Similarly,in the computer system, all major calculation comprehensions are made inside the C.P.Uand the CPU is also responsible for activating and controlling the operations of other unitsof a computer system.THE SYSTEM CONCEPT:You might have observed by now that we have been referring to a computer as a system(computer system).What we be the reason behind this? To know the answer let us first consider the definitionof a system.A system system is a group of integrated parts that have the common purpose of achievingsome objective(s). So, the following three characteristics are key to a system: 1. A system has more then one elements. 2. All the elements of the system are logically related. 3. All the elements of a system are controlled in such a way that the system goal is achieved.Since a computer is made up of integrated components (input, output, storage and CPU)that work together to perform the steps called for in the program being executed, it is asystem. The input and output units cannot function until they receive signals from theCPU. Similarly, the storage unit or the CPU is of on use. So the usefulness of each unitdepends on other units and can be realized only when all units are put together (integrated)to form a system. 33