User:Krishnachippy/sandbox

Definition and scope of Information Technology 1.	Introduction Information Technology is widely used at every corners of the globe. The impact of IT can be seen in area like education,healthcare,financialinstitutions,businessenterprises,industry and even in entertainment sectors 1.1 Different views on IT- Business people - think IT implies automation of financial institutions Communication Engineer - feels IT as Multimedia communication ,teleconferencing Computer Engineers – Computer networking and creation of computer database Web Developers- Web Technology and Internets In actuality, information technology is the use of computers and software to manage information. Definition:- Information technology is defined as the science, art and of course, the technology of acquiring the information, storing the information, structuring the information, compressing and transmitting the information and at last processing and interpreting this information. Information technology is a general term that describes any technology that helps to produce, manipulate, store, communicate, and/or disseminate information. 1.2 Basic concepts of IT 1.2.1. Data base Management Systems DBMS is the collection of inter related data and the set of programs to access those data. Database contains huge amount of storage space for storing data. DBMS allows store, retrieve and update data in the database. Example Student database. Inter related data Student no	Student name	Branch	 Address 1	Asha	CS	Xyz 2	Aparna	IT	Abc

Using the programs we can insert new student records, delete, retrieve and update the data stored in the database. 1.2.2.Multimedia Communication –Multimedia refers to the integration of multiple media ,such as Text, video, sound and animation ,which together can multiply the impact of our message. Components of Multimedia: a. Text : Text in the form of words ,sentences and paragraphs ,is used to communicate thoughts, ideas and facts in every aspects of life. Text is displayed in a variety of styles called Fonts. Text is used for a variety of purposes that include: 1.	Providing identification of objects such as pictures 2.	Delivering information in the form of captions and bulk text 3.	Assisting the user in navigating around the application b. Graphics :It is in the form of pictures ,clip art and photographs  .They are created using a variety of tools including paint and drawing software, image scanners and digital cameras. c. Digital Audio: Sound comprises the spoken words, voice, music and even noise. Three classes of sound ,voice ,music and sound effects d. Digital Video: video is simply moving pictures. It is composed of sequence of still pictures called frames. Each frame is composed of a two dimensional array of pixels, covering the horizontal and vertical direction e.Animation :It is the use of computer generated images to convey motion. Animation frames are created with software tools rather than using live or recorded video 1.2.3.Networking Computer Networking provides communication between computer systems or devices .Computer networks is the collection of connected computers that are able to exchange information. Computers are inter-connected through coaxial cables(cable TV), twisted pair(telephone line), optical fiber etc. •	Local area network (LAN), which is usually a small network constrained to a small geographic area. An example of a LAN would be a computer network within a building. •	Metropolitan area network (MAN), which is used for medium size area. examples for a city or a state. •	Wide area network (WAN) that is usually a larger network that covers a large geographic area.

Network Services: a)	 Telephone Services b)	Radio and TV Broadcasting c)	Email d)	World Wide Web e)	Video Conferencing 1.2.4.E-commerce Electronic commerce, commonly known as e-commerce or e-business consists of the buying and selling of products or services over electronic systems such as the Internet and other computer networks. Aspects of e-commerce include: •	online retail selling on websites with online catalogs(24 hrs showcase). •	Electronic Data Interchange (EDI), is paperless exchange of business information. (point-to-point): It is used to transfer electronic documents from one computer system to another, i.e. from one trading partner to another trading partner •	Email, instant messaging and social networking as media for reaching prospects and established customers. •	Business-to-business buying and selling.( Electronic commerce that is conducted between businesses is referred to as business-to-business or B2B) •	The security of business transactions. Security includes authenticating business transactions, controlling access to resources such as Web pages for registered or selected users, encrypting communications, and, in general, ensuring the privacy and effectiveness of transactions 1.2.5.Internet and Web technology Internet :The interconnection of multiple network into a single large network is called an internetwork, which is abbreviated as an internet. It is a network of networks. Connecting hardware together does not make an internet. Interconnected computers need software before they can communicate. The World Wide Web, abbreviated as WWW and commonly known as the Web, is a system of interlinked documents accessed via the Internet. With a web browser, one can view web pages that may contain text, images, videos, and other multimedia and navigate between them by using hyperlinks. Ex: Internet Explorer, Mozilla Firefox Web Technology - A system for information distribution, a system for linking information, stored on many computers Ex: HTML – Hyper Text Mark- up Language  : web pages can be written  using HTML Von Neumann architectures In early days the task of entering and altering programs was extremely tedious. The programming process could be facilitated if the program could be represented in a form suitable for storing in memory alongside the data. Then, a computer could get its instructions by reading them from memory, and a program could be set of altered by setting the values of a portion of memory. This idea, known as the Stored-program concept. In 1946, von Neumann and his colleagues began the design of a new stored-program computer, referred to as the IAS computer, at the Princeton Institute for Advanced Studies. The IAS computer, although not completed until 1952, is the prototype of all subsequent general-purpose computers. The von Neumann architecture is a design model for a stored-program digital computer that uses a central processing unit (CPU) and a single separate storage structure ("memory") to hold both instructions and data. It is named after the mathematician and early computer scientist John von Neumann. A von Neumann Architecture computer has five parts: an arithmetic-logic unit, a control unit, a memory, some form of input/output and a bus that provides a data path between these parts. It consists of : A main memory, which stores both data and instructions. An arithmetic-logical unit (ALU) capable of operating on binary data. A control unit, which interprets the instructions in memory and causes them to be executed. Input and output (I/O) equipment operated by the control unit. Figure shows the general structure of the IAS computer: Digital Computer It is a fast electronics calculating machine that accepts digitized input information, processes it according to a list of internally stored instructions, and produces the resulting output information. The list of instructions is called a computer program, and internal storage is called computer memory. A digital computer stores data in the form 0’s and 1’s. A ‘0’ or ‘1’is called a bit. A combination of 8 bits is called a byte. A sequence of 4 bits is called a nibble.

Functional Units of a Computer Computer consists of: •	Input unit •	Memory Unit •	Arithmetic and Logic Unit(ALU) •	Control Unit •	Output Unit

Input unit Data and instructions must enter the computer system before any computation can be performed on the supplied data. The input unit that links the external environment performs this task with the computer system. However regardless of the form they receive data; all input devices must provide a computer with data that are transformed in to the binary codes that the primary memory of a computer is designed to accept.

The following are the functions of input devices: It accepts the list of instructions and data from outside world. It converts these instructions and data into computer acceptable form. It supplies the converted instructions and data to the computer system for further processing. The examples of input devices are: keyboard, mouse, joystick, scanner. Output Unit This supplies instructions and results of computation to outside world. Thus it links the computer with the external environment. As computer works with binary codes the results produced are also in the binary form. So before supplying to the outside world it should have to be converted to human acceptable form. The main functions of output devices are: It accepts the results produced by the computers, which are in coded form and hence cannot be easily understood by the user. It converts the code to human readable form. It supplies the converted results to the outside world. The examples of output devices are: monitors, printers, plotters.

MEMORY UNIT (Storage Unit) The data and instructions that are entered into the computer system through input units have to be stored inside the computer system before the actual processing starts. Similarly the results produced in the computer after processing must also kept somewhere inside the computer before passes to the output section. The intermediate results formed also should have to be preserved for ongoing processing. The functions of memory unit are to store: a)	All the data to be processed and the instructions required for processing. b)	Intermediate results of processing. c)	Final results of processing before released to an outside device. Arithmetic and Logic Unit (ALU) The ALU of a computer is the place where the actual execution of the instruction takes place during processing .All of the arithmetic and logical operations are carried out in ALU. Any arithmetic and logical operation, is initiated by bringing the required operands into the processor where the operation is performed by the ALU. When operands are brought into the processor, they are stored in high speed storage elements called registers. Control Unit The memory, arithmetic and logic, and input and output units store and processing formation and perform input and output operations. The operations of all these units are coordinated by the control unit. That is control unit is the nerve center that sends control signals to other units and senses their states.	Basic Operational Concepts

The fig .shows how the memory and the processor can be connected. In addition to the ALU and control circuitry, the processor contains a number of registers used for several different purposes. The instruction register (IR) holds the instruction that is currently being executed. The program counter (PC) keeps track of the execution of  a program. It contains the memory address of the next instruction to be fetched and executed. During the execution of  an instruction ,the contents of the PC are updated to correspond to the address of the next instruction that is  to be fetched from the memory. R 0 – R n-1, these are general purpose registers. Memory address register (MAR) and memory data register (MDR) facilitate communication with the memory. The MAR holds the address of the location to be accessed. The MDR contains the data to written into or read out of the addressed location. Execution of the program starts when the PC is set to point to the first instruction of the program. The contents of PC are transferred to the MAR and a Read control signal is sent to the memory. After the time required to access the memory elapses, the addressed word is read out of the memory and loaded into the MDR. Next, the contents of the MDR are transferred to the IR. At this point the instruction is ready to be decoded and executed. If the instruction involves an operation to be performed by the ALU, it is necessary to obtain the required operands. If an operand resides in the memory(it could also be in a general purpose register in the processor), it has to be fetched by sending its address to the MAR and initiating a Read cycle. When the operand has been read from the memory into the MDR, it is transferred from the MDR to the ALU. After one or more operands are fetched in this way, the ALU can perform the desired operation. If the result of this operation is to be stored in the memory, the result is sent to the MDR, and a Write cycle is initiated. At some point during the execution the current instruction, the contents of the PC are incremented so that the PC points to the next instruction to be executed.

Bus structures A group of lines that serves as a connecting path for several devices is called a bus. In addition to the lines that carry data the bus must have lines for address and control purposes. The simplest way to interconnect functional units is to use a single bus. All units are connected to this bus. Because the bus can be used for only one transfer at a time, only two units can actively use the bus at any given time. The main virtue of the single –bus structure is its low cost and its flexibility for attaching peripheral devices. The systems that contain multiple buses achieve more concurrency in operations by allowing two or more transfers to be carried out at the same time. This leads to better performance but at an increased cost. Buses can be classified into two : 	Internal bus Internal bus connects CPU, system memory and all other components on the motherboard.

	External bus The external bus connects the different external devices, peripherals, I/O ports, and drive connection to the rest of the computer.

CPU- single bus organization To execute a program, the processor fetches one instruction at a time and performs the operations specified. Instructions are fetched from successive memory locations until a branch or a jump instruction is encountered. The processor keeps track of the address of the memory location containing the next instruction to be fetched using the program counter, PC. After fetching an instruction, the contents of the PC are updated to point to the next instruction in the sequence. A branch instruction may load a different value into the PC. Another key register in the processor is the instruction register, IR. Suppose that each instruction comprises 4 bytes, and that it is stored in one memory word. To execute an instruction, the processor has to perform the following three steps: I. Fetch the contents of the memory location pointed to by the PC. The contents of this location are interpreted as an instruction to be executed. Hence, they are loaded into the IR. Symbolically, this can be written as IR PC 2. Assuming that the memory is byte addressable, increment the contents of the PC by 4, that is, PC [PC] +4 3. Carry out the actions specified by the instruction in the IR. In cases where an instruction occupies more than one word, steps I and 2 must be repeated as many times as necessary to fetch the complete instruction. These two steps are usually referred to as the fetch phase; step 3 constitutes the execution phase. Figure 1.1 shows an organization in which the arithmetic and logic unit (ALU) and all the registers are interconnected via a single common bus. This bus is internal to the processor and should not be confused with the external bus that connects the processor to the memory and I/O devices. The data and address lines of the external memory bus are shown in Figure 1.1 connected to the internal processor bus via the memory data register, MDR, and the memory address register, MAR, respectively. Register MDR has two inputs and two outputs. Data may be loaded into MDR either from the memory bus or from the internal processor bus. The data stored in MDR may be placed on either bus. The input of MAR is connected to the internal bus, and its output is connected to the external bus. The control lines of the memory bus are connected to the instruction decoder and control logic block. This unit is responsible for issuing the signals that control the operation of all the units inside the processor and for interacting with the memory bus. The number and use of the processor registers R0 through R(n - 1) vary considerably from one processor to another. Registers may be provided for general-purpose use by the programmer. Some may be dedicated as special-purpose registers, such as index registers or stack pointers. Three registers, Y, Z, and TEMP in Figure 1.1, have not been mentioned before. These registers are transparent to the programmer, that is, the programmer need not be concerned with them because they are never referenced explicitly by any instruction. They are used by the processor for temporary storage during execution of some instructions. These registers are never used for storing data generated by one instruction for later use by another instruction. The multiplexer MUX selects either the output of register Y or a constant value 4 to be provided as input A of the ALU. The constant 4 is used to increment the contents of the program counter. We will refer to the two possible values of the MUX control input Select as Select4 and SelectY for selecting the constant 4 or register Y, respectively. As instruction execution progresses, data are transferred from one register to another, often passing through the ALU to perform some arithmetic or logic operation. The instruction decoder and control logic unit is responsible for implementing the actions specified by the instruction loaded in the IR register. The decoder generates the control signals needed to select the registers involved and direct the transfer of data. The registers, the ALU, and the interconnecting bus are collectively referred to as the datapath. With few exceptions, an instruction can be executed by performing one or more of the following operations in some specified sequence: • Transfer a word of data from one processor register to another or to the ALU • Perform an arithmetic or a logic operation and store the result in a processor register • Fetch the contents of a given memory location and load them into a processor register • Store a word of data from a processor register into a given memory location

Fig.1.1 Single bus organization of the data path inside a processor

REGISTER TRANSFERS Instruction execution involves a sequence of steps in which data are transferred from one register to another. For each register, two control signals are used to place the contents of that register on the bus or to load the data on the bus into the register. This is represented symbolically in Figure 1.2. The input and output of register Ri are connected to the bus via switches controlled by the signals Riin and Riout, respectively. When Riin is set to 1, the data on the bus are loaded into Ri. Similarly, when Rioutis set to 1, the contents of register Ri are placed on the bus. While Riout is equal to 0, the bus can be used for transferring data from other registers. Suppose that we wish to transfer the contents of register Rl to register R4. This can be accomplished as follows: •	Enable the output of register R1 by setting R1out to 1. This places the contents of R 1 on the processor bus. •	Enable the input of register R4 by setting R4in to 1. This loads data from the processor bus into register R4.

Fig.1.2 Input and output gating for the registers in fig 1.1