E -MAIL AND INTERNET

1. UNIT 1 E -MAIL AND INTERNET E-mail Electronic mail, often abbreviated as email, e.mail or e-mail, is a method of exchanging digital messages. E-mail systems are based on a store-and-forward model in which e-mail computer server systems accept, forward, deliver and store messages on behalf of users, who only need to connect to the e-mail infrastructure, typically an e-mail server, with a network-enabled device (e.g., a personal computer) for the duration of message submission or retrieval. Originally, e-mail was always transmitted directly from one user's device to another's; nowadays this is rarely the case. An electronic mail message consists of two components, the message header, and the message body, which is the email's content. The message header contains control information, including, minimally, an originator's email address and one or more recipient addresses. Usually additional information is added, such as a subject header field. Header fields The message header should include at least the following fields: From: The e-mail address, and optionally the name of the author(s). In many e- mail clients not changeable except through changing account settings. To: The e-mail address(es), and optionally name(s) of the message's recipient(s). Indicates primary recipients (multiple allowed), for secondary recipients see Cc: and Bcc: below. Subject: A brief summary of the topic of the message. Date: The local time and date when the message was written. Like the From: field, many email clients fill this in automatically when sending. The recipient's client may then display the time in the format and time zone local to her. Message-ID: Also an automatically generated field; used to prevent multiple delivery and for reference in In-Reply-To: Email is simply the shortened form of electronic mail, a protocol for receiving, sending and storing electronic messages. Email has gained popularity with the spread of the Internet. In many cases, email has become the preferred method of communication. The following sections describe the key features of email. https://www.ThesisScientist.com

2. Email Is A Push Technology: Email is delivered to the recipient so they don't have to work to get it -- they just open their Inbox and there it is. Email Waits For You: Email is particularly convenient because it is asynchronous; it waits for you and fits into your schedule instead of demanding that you structure your activities to synchronize with those you communicate with. Email Has The Power Of One-To-Many : You can send an email to several people in one simple action. Communications can be divided into four types depending on the number of parties participating in the information transfer: (1) one-to-one, (2) one-to- many, (3) many-to-one, and (4)many-to-many. Each type of communication has its own attributes and strengths. For example, the typical phone call is one-to-one, and the typical meeting is many-to-many. Email is the most successful one-to-many technology, with respect to both sending and receiving: Sending. You can send an email to more than one person at a time, for example to everyone in your family, or to a group of friends. Receiving. You can receive information that has been mailed to more than one person, for example an announcement sent to hundreds of people on a mailing list. Free of Cost: Email is by far the most inexpensive form of communication across global distances. You can send email to anyone in the world, no matter how far away, at no extra cost to you. Use of regular paper mail, telephone, or telegram E mail address E mail address identifies an email box to which email messages are delivered. An example format of an email address is narendra@example.net which is read as narendra at example dot net. Many earlier email systems used different address formats. Overview Transport of email across the Internet uses the Simple Mail Transfer Protocol (SMTP), which is defined in Internet standards RFC 5321 and RFC 5322, while mailboxes are most often accessed with the Post Office Protocol (POP) and the Internet Message Access Protocol (IMAP). Email addresses, such as narendra@gmail.com, have two parts. The part before the @ sign is the local-part of the address, often the username of the recipient (narendra), and the part after the @ sign is a domain name to which the email message will be sent (gmail.com). An SMTP server looks up the domain name using the Domain Name System, which is a distributed database. A server queries the DNS for any mail exchanger records (MX https://www.ThesisScientist.com

3. records) to find the host name of a designated mail transfer agent(MTA) for that address. That way, the organization holding the delegation for a given domain —the mailbox provider— can define which are the target hosts for all email destined to its domain. The mail exchanger does not need to be located in the domain of the destination mail box, it must simply accept mail for the domain. The target hosts are configured with a mechanism to deliver mail to all destination mail boxes. The local-part of an address, is defined to be opaque to intermediate mail relay systems except the final mailbox host. For example, it must not be assumed to be case-insensitive. Multiple email addresses may point to the same mailbox. Conversely, a single email address may be an alias and have a distribution function to many mailboxes. Email aliases, electronic mailing lists, sub-addressing, and catch-all addresses, the latter being mailboxes that receive messages irrespectively of the local part, are common patterns for achieving such results. The addresses found in the header fields of an email message are not the ones used by SMTP servers to deliver the message. Servers use the so-called message envelope to route mail. While envelope and header addresses may be equal, forged email addresses are often seen in spam, phishing, and many other internet-based scams. This has led to several initiatives which aim to make such forgeries easier to spot. Electronic mailing list An electronic mailing list is a special usage of email that allows for widespread distribution of information to many Internetusers. It is similar to a traditional mailing list — a list of names and addresses — as might be kept by an organization for sending publications to its members or customers, but typically refers to four things — a list of email addresses, the people ("subscribers") receiving mail at those addresses, the publications (email messages) sent to those addresses, and areflector, which is a single email address that, when designated as the recipient of a message, will send a copy of that message to all of the subscribers. Electronic mailing lists work Electronic mailing lists are usually fully or partially automated through the use of special mailing list software and a reflector address that are set up on a server capable of receiving email. Many electronic mailing list servers have a special email address in which subscribers (or those that want to be subscribers) can send commands to the https://www.ThesisScientist.com

4. server to perform such tasks as subscribing and unsubscribing, Electronic mailing list servers can be set to forward messages to subscribers of a particular mailing list either individually as they are received by the list server Types Announcement list One type of electronic mailing list is an announcement list, which is used primarily as a one-way conduit of information and can only be "posted to" by selected people. This may also be referred to by the term newsletter. Newsletter and promotional emailing lists are employed in various sectors as parts of direct marketing campaigns. Discussion list Another type of electronic mailing list is a discussion list, in which any subscriber may post. On a discussion list, a subscriber uses the mailing list to send messages to all the other subscribers, who may answer in similar fashion. Thus, actual discussion and information exchanges can happen. Mailing lists of this type are usually topic-oriented (for example, politics, scientific discussion, joke contests), and the topic can range from extremely narrow to "whatever you think could interest us". In this they are similar to Usenet newsgroups, and share the same aversion to off-topic messages. The term discussion group encompasses both these types of lists and newsgroups. Feature of Internet: The web leverages the key features of the Internet and makes them widely accessible to the public. Key features of the web in particular are its ease of use, universal accessibility, and ability to be quickly searched: Ease of use. The web can be immediately used by anyone already familiar with a computer window. The only special features are links, which are as natural and intuitive to use as pressing a button. This ease of use enabled the rapid adoption of the web in the 1990's, and led to the establishment of the Internet around the world. Universal access. The open design of the web makes it easy to build web browsers for a wide range of devices. Web browsers have been deployed on cell phones and personal organizers, and the web is now the standard interface for providing access to information. https://www.ThesisScientist.com

5. Search capabilities. The development of search sites greatly multiplied the power and usefulness of the web by providing the capability to effectively search the content of millions of web pages in seconds. ISP: (Internet service provider) An Internet service provider (ISP), also sometimes referred to as an Internet access provider (IAP), is a company that offers its customers access to the Internet. The ISP connects to its customers using a data transmission technology appropriate for delivering Internet Protocol datagrams, such as dial-up, DSL, cable modem, wireless or dedicated high-speed interconnects. An ISP (Internet Service Provider) is a company that collects a monthly or yearly fee in exchange for providing the subscriber with Internet access. An ISP might provide dial-up service, cable, DSL, or other types of Internet access. Some ISPs are local while others are national. A national ISP will provide access throughout most of the nation, while a local ISP will only serve subscribers in a limited geographical region. ISPs may provide Internet e-mail accounts to users which allow them to communicate with one another by sending and receiving electronic messages through their ISP's servers. ISPs may provide other services such as remotely storing data files on behalf of their customers, as well as other services unique to each particular ISP. ISPs employ a range of technologies to enable consumers to connect to their network. For users and small businesses, the most popular options include dial-up, DSL (typically Asymmetric Digital Subscriber Line, ADSL), broadband wireless, cable modem, fiber to the premises (FTTH), and Integrated Services Digital Network (ISDN) (typically basic rate interface). For customers with more demanding requirements, such as medium-to-large businesses, or other ISPs, DSL (often SHDSL or ADSL), Ethernet, Metro Ethernet, Gigabit Ethernet, Frame Relay, ISDN (BRI or PRI), ATM, satellite Internet access and synchronous optical networking (SONET) are more likely to be used. Typical home user connection Dial-up DSL Broadband wireless access Cable Internet FTTH ISDN Wi-Fi https://www.ThesisScientist.com

6. ISP services range in price according to the package offered, and type of service. Dial-up is least expensive, and perks will vary greatly between ISPs. Some offer multiple email accounts, others vast amounts of webspace, and still others discounts for paying in advance. DSL and cable companies will also differ, so carefully read through offerings before deciding. If you are getting an ISP other than cable, you will likely have choices. There are many websites that offer reviews from present subscribers of various ISPs, which might be helpful in making a decision. FTP: (File Transfer Protocol): File Transfer Protocol (FTP) is a standard network protocol used to exchange and manipulate files over a TCP/IP based network, such as the Internet. FTP is built on a client-server architecture and utilizes separate control and data connections between the client and server applications. Applications were originally interactive command-line tools with a standardized command syntax, but graphical user interfaces have been developed for all desktop operating systems in use today. FTP is also often used as an application component to automatically transfer files for program internal functions. FTP can be used with user-based password authentication or with anonymous user access The key definition to remember is the term "protocol," which means a set of rules or standards that govern the interactions between computers. It is a key component in many terms that are now taken for granted: Transmission Control Protocol / Internet Protocol or TCP/IP, the governing standards for internet communications; Hyper Text Transfer Protocol or HTTP, which established the benchmarks for internet addresses and communications between two computers in the internet; and File Transfer Protocol (FTP) which, as has been said, sets the rules for transferring files between computers. The primary objective in the formulation of File Transfer Protocols was to make file transfers uncomplicated and to relieve the user of the burden of learning the details on how the transfer is actually accomplished. The result of all these standards and rules can be seen in today's web interactions, where pointing-and-clicking (with a mouse) initiates a series of actions that the typical internet user does not see or even remotely understand. Purpose To promote sharing of files (computer programs and/or data). To encourage indirect or implicit use of remote computers. To shield a user from variations in file storage systems among different hosts. To transfer data reliably, and efficiently. Data format While transferring data over the network, several data representations can be used. The two most common transfer modes are: ASCII mode Binary mode: In "Binary mode", the sending machine sends each file byte for byte and as such the recipient stores the bytestream as it receives it. (The FTP standard calls this "IMAGE" or "I" mode) https://www.ThesisScientist.com

7. In ASCII mode, any form of data that is not plain text will be corrupted. When a file is sent using an ASCII-type transfer, the individual letters, numbers, and characters are sent using their ASCII character codes. The receiving machine saves these in a text file in the appropriate format (for example, a Unix machine saves it in a Unix format, a Windows machine saves it in a Windows format). Hence if an ASCII transfer is used it can be assumed plain text is sent, which is stored by the receiving computer in its own format. HTTP: (Hypertext Transfer Protocol) HTTP or Hyper Text Transfer Protocol (HTTP) is the communications protocol which enables browsing the Web. Short for HyperText Transfer Protocol, the underlying protocol used by the World Wide Web. HTTP defines how messages are formatted and transmitted, and what actions Web servers and browsers should take in response to various commands. For example, when you enter a URL in your browser, this actually sends an HTTP command to the Web server directing it to fetch and transmit the requested Web page. The other main standard that controls how the World Wide Web works is HTML, which covers how Web pages are formatted and displayed. HTTP is called a stateless protocol because each command is executed independently, without any knowledge of the commands that came before it. This is the main reason that it is difficult to implement Web sites that react intelligently to user input. This shortcoming of HTTP is being addressed in a number of new technologies, including ActiveX, Java, JavaScript and cookies. Hypertext Transfer Protocol (HTTP) is an application-level protocol for distributed, collaborative, hypermedia information systems.Its use for retrieving inter-linked resources, called hypertext documents HTTP session An HTTP session is a sequence of network request-response transactions. An HTTP client initiates a request. It establishes a Transmission Control Protocol (TCP) connection to a particular port on a host Computers on the World Wide Web use the HyperText Transfer Protocol to talk with each other. The HTTP provides a set of instructions for accurate information exchange. The communication between the client (your browser) and the server (a software located on a remote computer) involves requests sent by the client and responses from the server. Each client-server transaction, whether a request or a response, consists of three main parts 1.A response or request line https://www.ThesisScientist.com

8. 2.Header information 3.The body A client connects to the server at port 80 (unless it has been changed by the system administrator) and sends a request. The request line from the client consists of a request method, the address of the file requested and the HTTP version number. WORLD WIDE WEB WWW: The World Wide Web, abbreviated as WWW and W3 and commonly known as The Web, is a system of interlinked hypertext documents contained on the Internet. With a web browser, one can view web pages that may contain text, images, videos, and other multimedia and navigate between them using hyperlinks. Using concepts from earlier hypertext systems. "The World-Wide Web (W3) was developed to be a pool of human knowledge, which would allow collaborators in remote sites to share their ideas and all aspects of a common project." [4] If two projects are independently created, rather than have a central figure make the changes, the two bodies of information could form into one cohesive piece of work. Classification of Computer: Computers are classified according to their data processing speed, amount of data that they can hold and price. Generally, a computer with high processing speed and large internal storage is called a big computer. Due to rapidly improving technology, we are always confused among the Depending upon their speed and memory size, computers are classified into following four main groups. categories of computers. 1.Supercomputer. 2.Mainframe computer. 3.Mini computer. 4.Microcomputer. 1.Supercomputer: Supercomputer is the most powerful and fastest, and also very expensive. It was developed in 1980s. It is used to process large amount of data and to solve the complicated scientific problems. It can perform more than one trillions calculations per second. It has large number of processors connected parallel. So parallel processing is done in this computer. In a single supercomputer thousands of users can be connected at the same time and the supercomputer handles the work of each user separately. Supercomputer are mainly used for: https://www.ThesisScientist.com

9. Weather forecasting. Nuclear energy research. Aircraft design. Automotive design. Online banking. 2. Mainframe Computers: Mainframe computers are also large-scale computers but supercomputers are larger than mainframe. These are also very expensive. The mainframe computer specially requires a very large clean room with air-conditioner. This makes it very expensive to buy and operate. It can support a large number of various equipments. It also has multiple processors. 3. Minicomputers: These are smaller in size, have lower processing speed and also have lower cost than mainframe. These computers are known as minicomputers because of their small size as compared to other computers at that time. The capabilities of a minicomputer are between mainframe and personal computer. These computers are also known as midrange computers. The minicomputers are used in business, education and many other government departments. Although some minicomputers are designed for a single user but most are designed to handle multiple terminals. 5.MicrocomputerThe microcomputers are also known as personal computers or simply PCs. Microprocessor is used in this type of computer. These are very small in size and cost. The IBM’s first microcomputer was designed in 1981 and was named as IBM-PC. After this many computer hardware companies copied the design of IBM-PC. The term ―PC-compatible‖ refers any personal computer based on the original IBM personal computer design. There are many characteristics of a computer system 1. Speed:- A computer is a very high speed device they can perform or execute more than 100 millions of attraction for per second. Thus result high speed performance is performance is very fast. 2. Accuracy:- The accuracy of a computer is high and the degree of a particulars computer depend upon its designed but for a computer accuracy calculation with the same accuracy error accuracy in a computer there are many to human gather than technological or by the program due to accurate data in a wrong direction. 3. Diligence:- A human being get boar and tired and loss of efficiency and securely in repeated task but a computer never get and tired it will perform a calculation with scene speed same accuracy for any number of times. 4. Storage:- https://www.ThesisScientist.com

10. The high speed of calculation of computer reserve into requires more and more internal memory. The storage memory capacity of interred to megabyte and beg byte a good computer score 100 megabyte and beg byte. 5. Versatility:- The computer are reliable very accurate and can be used to solve the program related to difference field at one moment it may solve a computer stymie program and next it may be playing a game and may busy in other database problem. 6. Reliable:- The computer e reliable very accuracy and do not mistake in earth mastic calculation the reason is not hard ware level it does not require human interfere between its processing operations. 7. Reductions in paper work:- The use of computer for data processing has help for business organization with the increasing problem of papers handling. 8. Reduction in cost:- The investment of installing is high with after that it reduce the cost of an operation. 9. Retrieval capacity:- A computer has not a high storage capacity rather then it can between the storage there in second accuracy it. Limitation of a computer system 1.A computer has no brain intelligence of it’s on it does what is ask to does any sequence. 2.Computer can only do a job which can be express. 3.The computer can work in a particular entailments temperature of 15-35 and free at heart. 4.It has no emotions of fillings life human being in other words it has no hearts and sow being a simple machine. Operating system An operating system (OS) is an interface between hardware and user which is responsible for the management and coordination of activities and the sharing of the resources of a computer that acts as a host for computing applications run on the machine. As a host, one of the purposes of an operating system is to handle the details of the operation of the hardware. This relieves application programs from having to manage these details and makes it easier to write applications https://www.ThesisScientist.com

11. Operating systems offer a number of services to application programs and users. Applications access these services through system calls or, when available, application programming interfaces (APIs). By executing these system calls, or invoking these interfaces, the operating system can manage parameters in the background, or negotiate exchanges of signals or processes, relieving programs or processes in the foreground from the tedium of scrutinizing low level matters. Users may also interact with the operating system with some kind of software user interface like typing commands by using command line interface (CLI) or using a graphical user interface (GUI). DOS: Microsoft Disk Operating System) is an operating system for x86 based personal computers, which was purchased by Microsoft. It was the most commonly used member of the DOS family of operating systems, and was the main operating system for personal computers during the 1980s and 1990s. 8086-family computer. Each computer would have its own distinct hardware and its own version of MS-DOS, Originally MS-DOS was designed to be an operating system that could run on any UNIX Operating System: is a computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna. Today the term Unix is used to describe any operating system that conforms to Unix standards, meaning the core operating system operates the same as the original Unix operating system. Today's Unix systems are split into various branches, developed over time by AT&T as well as various commercial vendors and non-profit organizations. https://www.ThesisScientist.com

12. Unix environment and the client-server program model were essential elements in the development of the Internet and the reshaping of computing as centered in networks rather than in individual computers. Unix was designed to be portable, multi-tasking and multi-user in a time-sharing configuration. Unix systems are characterized by various concepts: the use of plain text for storing data; a hierarchical file system; treating devices and certain types of inter- process communication (IPC) as files; and the use of a large number of software tools, Feature: Multitasking is a method by which multiple tasks, also known as processes, share common processing resources such as a CPU. In the case of a computer with a single CPU, only one task is said to be running at any point in time, meaning that the CPU is actively executing instructions for that task. Multi-user is a term that defines an operating system or application software that allows concurrent access by multiple users of a computer Time-sharing is sharing a computing resource among many users by means of multiprogramming and multi-tasking. Unix operating systems are widely used in both servers and workstations. The Representation of Data Inside Computer: computer works with binary number system that is consist of only two digits zero and one. Inside the computer binary number is represented by an electrical pulse. One means a pulse of electricity and zero means no pulse. All the data enters into the computers first converts into the binary number system. One digit in binary number system is called bit and combination of eight bits is called byte. A byte is the basic unit that is used to represent the alphabetic, numeric and alphanumeric data. Data is the combination of characters, numbers and symbols collected fro a specific purpose. Data is divided into three types; alphabetic data, numeric data and alphanumeric data. Numeric data consist of ten digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, two signs + and – and decimal point . There are different types of number system that are used to represent numeric data. These number systems are decimal number system, binary number system, octal number system and hexadecimal number system. Alphabetic data is used to represent 26 alphabetic. It consist of capital letters from A to Z, small letters from a to z and blank space. Alphabetic data is also called non numeric data. Alphanumeric data used to represent alphabetic data, numeric data, special character. Computer is a system to manipulate data. Monitor, where we see data, is not the place to store them (though one of the police team had ceased the monitor to investigate a case of https://www.ThesisScientist.com

13. data theft!). It is the secondary storage devices (hard disk, floppy disk, CD, DVD, etc.) where the data are stored. Whatever we write through the keyboard or try to push through the various input devices, the corresponding input devices convert them first into digital signals to produce 0 or 1 (bits). These continuous streams of bits are then stored or represented signifying the non-availability or availability of the voltage. To avoid further ambiguity in retrieval, these bits are stored and accessed in a group, say 8 bits together. The group of 8 bits is called byte and thus the higher units of bit calculation are the KB (1 KB = 1024 bytes), MB (1 MB = 1024 KB), GB (1 GB = 1024 MB), etc. There exist several kinds of data such as Textual, Numerical, Alphanumerical, logical, Pictorial or Audiovisual. Each type of data has some pre-defined way of representation and other behaviour inside the computer. The textual data are the alphabetic character set of any language whereas the digits constitute the numeric part of the data. The mixture of alphabetic and numeric data together form the alphanumeric character sets. The logical data are those that help to analyse the comparison concept. Pictures and sounds create the pictorial and audiovisual data for the computer. Digital Computer: A computer that stores data in terms of digits (numbers) and proceeds in discrete steps from one state to the next. The states of a digital computer typically involve binary digits which may take the form of the presence or absence of magnetic markers in a storage medium (see memory), on-off switches or relays. In digital computers, even letters, words and whole texts are represented digitally. Computer capable of solving problems by processing information expressed in discrete form. By manipulating combinations of binary digits (see binary code), it can perform mathematical calculations, organize and analyze data, control industrial and other processes, and simulate dynamic systems such as global weather patterns A digital computer is an electronic computing machine that uses the binary digits (bits) 0 and 1 to represent all forms of information internally in digital form. Every computer has a set of instructions that define the basic functions it can perform. Sequences of these instructions constitute machine-language programs that can be stored in the computer and used to tailor it to an essentially unlimited number of specialized applications. Calculators are small computers specialized for mathematical computations. General- purpose computers range from pocket-sized personal digital assistants (notepad computers), to medium-sized desktop computers (personal computers and workstations), to large, powerful computers that are shared by many users via a computer network. The vast majority of digital computers now in use are inexpensive, special-purpose microcontrollers that are embedded, often invisibly, in such devices as toys, consumer electronic equipment, and automobiles. A device that processes numerical information; more generally, any device that manipulates symbolic information according to specified computational procedures. The term digital computer—or simply, computer—embraces calculators, computer workstations, control computers (controllers) for applications such as domestic appliances and industrial processes, data-processing systems, microcomputers, https://www.ThesisScientist.com

14. microcontrollers, multiprocessors, parallel computers, personal computers, network servers, and supercomputers. The main data-processing elements of a computer reside in a small number of electronic integrated circuits (ICs) that form a microprocessor or central processing unit (CPU). Electronic technology allows a basic instruction such as ―add two numbers‖ to be executed many millions of times per second. Other electronic devices are used for program and data storage (memory circuits) and for communication with external devices and human users (input-output circuits). Nonelectronic (magnetic, optical, and mechanical) devices also appear in computers. They are used to construct input-output devices such as keyboards, monitors (video screens), secondary memories, printers, sensors, and mechanical actuators. https://www.ThesisScientist.com

15. Computer Memory Computer data storage, often called storage or memory, refers to computer components, devices, and recording media that retain digital data used for computing for some interval of time. Computer data storage provides one of the core functions of the modern computer, that of information retention. It is one of the fundamental components of all modern computers, and coupled with a central processing unit (CPU, a processor), implements the basic computer model used since the 1940s. n contemporary usage, memory usually refers to a form of semiconductor storage known as random-access memory (RAM) and sometimes other forms of fast but temporary storage. Similarly, storage today more commonly refers to mass storage — optical discs, forms of magnetic storage like hard disk drives, and other types slower than RAM, but of a more permanent nature. Historically, memory and storage were respectively called main memory and secondary storage. The terms internal memory and external memory are also used. A digital computer represents data using the binary numeral system. Text, numbers, pictures, audio, and nearly any other form of information can be converted into a string of bits, or binary digits, each of which has a value of 1 or 0. The most common unit of storage is the byte, equal to 8 bits. A piece of information can be handled by any computer whose storage space is large enough to accommodate the binary representation of the piece of information, or simply data. For example, using eight million bits, or about one megabyte, a typical computer could store a short novel. Primary storage Primary storage (or main memory or internal memory), often referred to simply as memory, is the only one directly accessible to the CPU. The CPU continuously reads instructions stored there and executes them as required. Any data actively operated on is also stored there in uniform manner. RAM:- RAM is the random memory. It is the internal memory of C.P.U for storing data. It is read write memory & it is volatile in nature. It is also called random excess memory. Then is randomly. It is fast & very expenses. The information in ram. It retain as there is power splay . When the power is swift off information store in the ram is last. Static RAM: - .Static RAM contain more than one transjector & capacitor there for more expensive. But it does not lose its charge. Dynamic Ram:- every cell of dynamic ram is made up of one trajectory & one capacitor on transjector were as a switch device that give to & status on & off the dynamic Ram store information in the form of charge on a capacitor. When transjector is on current is pass & capacitor get charge forming a one bit otherwise zero bit. But there is a leakage in the capacitor & the information get lost if the capacitor is not charge again https://www.ThesisScientist.com

16. the contain must be refresh reguralarly to ratfish in the memory so it is called dynamic Ram. Dynamic ram are cheap having high pack aging density & speed. Rom:- Rom is the read only memory. The memory from which we can only read. But cannot write. It is called Rom. This is non volatile in nature the information is store permanently in Rom. During manufacture the Rom spared interactions. That Rom started instructions. Those are required to start computer. When electricity is fast time on. This operation is referring to as bootstrap its size & costs both are lower than Ram. The contained of Rom are not lost when power supply is terminated like Ram. There are various types of rom. Types of Rom 1-E. Rom (Erasable read only memory)- E. Rom is the types of Rom. The contain of which can be erase. Making the Rom reusable. How ever the enraging remove of the chip from the C.P.U such chip are hardly suitable for use by the application programmer. 2-P. Rom (programmable read only memory) The P. Rom is a field of programmable device. It can be program only once & is not erasing. 3-E. P. Rom( erasable & programmable read only memory)- E. P. Rom can be erase by exposing it to ultraviolet light for a direction up to 40 minutes & E. P. Rom eraser achieved to device. Programming & electrical charge is tape & the charge is retain for than ten year. Because the charge has no leakage path. 4-E. E. P. Rom( electrically erasable & programmable read only memory)- E. E. P. Rom can be erase & reprogram about ten thousand times bought erasing & programming take about to ten second. The bought advantage of E. E. P. Rom is that. It is non volatile memory & can not update easily. While disadvantage are the high cost & at present. They are not completely non vale tile & the write operations take more time. Secondary memory- the main drop at primary memory is that it is volatile & its capacity is limited to manage this problem it is sport by addition memory. Which is more permanent nonvolatile & can grow to a limit of infinite? This memory is outside in C.P.U. but it sport main memory. So it is called secondary memory. Or external memory. The cost per bit of storage for this memory is very low & its operating speed is slow as compare to main memory. The auxiliary memory can store as much data required by the user at as long as its need. The secondary storage device are easy to handle & transport that is not possible with primary key. https://www.ThesisScientist.com

17. Types of secondary storage device. Take & disk is the two principal storage devices in a computer system. These storage device also non as bat the storage device & are use for a veracity of purpose such as to store file for data temporary storage of program. Main advantage of basic. These devices are external to C.P.U 7 the main memory are also term as secondary storage device. These are many secondary storage device are. 1:- magnetic tape:- magnetic tape is a popular & least expenses for storing data & files. The magnetic tape made is of plastic base coated path with on iron oxide coating. the wield of a tape can according to the particular system. The length of a reel of tape may from 1200 to 3600 feet. The data are store in a magnetic tape according their size a character is store along with width of the take in the formed of vertical frame with entered a with return at a time. One standard of a computer is 1600 & 16250 bit per inch. Advantage of magnetic tape. 1:-storage capacity: - the storage capacity of magnetic tape is very large. 2:- portable: - it is portable. 3:- cost: - magnetic tape is one of the cheap storage media. The cost per feet storing data on take is very fast. 4:- reusable: - the particular data can be deleted & other data can be store at the same place. The space can be using any number of times. Disadvantage. 1: - Non flexible– magnetic tap is not flexible media. 2:- Transmission speed:- The rate of data transfer is very slow in magnetic tap due serial nature of the device. 3:- Access time:- All the report prior to the requirement record access time is very large in magnetic tape. 4:- Interment problem:- The problem of dust humidity 7 high temphracer cause input output error. Magnetic disk: - Magnetic disk is a storage device. Which make be as the shape of gramophone record this disk is coated on box side with a fill of magnetic martial has the properly that can store ether 1 & 0 permanently. The disk mounted on a spindle connected to a motor rotate is very fast speed of the order of 3600 per second. Each disk is divided into number of & each track divided sector. There are per surface. Top surface of fast bottom of the last are not use for reading & writing. Then surface are used for storage purpose each surface has five hundred per tracks & each track has forty sectors. Advantage of magnetic disk:- 1:-storage capacity: - It can store a large volume of data. 2:- Transmission speed:- The rate of data transmission is fast magnetic disk. 3:- Access time:- access time with magnetic disk it is possible to access a record directly. So access time is less in this space magnetic disk. https://www.ThesisScientist.com

18. 4:- reusable: Reusable in this we can delete a particular data & store another data at the same place. 5:- flexible:- It is flexible . because it can use seqnencilly direct access storage device. Dis advantage. 1:- Cost:- cost of character storage. It hailer as compare to magnetic tape. 2:- Non human readable:- Non human readable data store in magnetic disk. It is non human readable from their form manual encoding not possible in magnetic disk. 3:- Non portable:- Non portable is very less is compare to magnetic tap. 4:- limited size record:- length of record which can be be store on it is limited by the size of disk track of disk sector. https://www.ThesisScientist.com