Computer software, or simply software, is that part of a computer system that consists of data or computer instructions, in contrast to the physical hardware from which the system is built. In computer science and software engineering, computer software is all information processed by computer systems, computer software includes computer programs and related non-executable data, such as online documentation or digital media. Computer hardware and software require each other and neither can be used on its own. At the lowest level, executable code consists of machine language instructions specific to an individual processor—typically a central processing unit, a machine language consists of groups of binary values signifying processor instructions that change the state of the computer from its preceding state. For example, an instruction may change the value stored in a storage location in the computer—an effect that is not directly observable to the user. An instruction may cause something to appear on a display of the computer system—a state change which should be visible to the user.
The processor carries out the instructions in the order they are provided, unless it is instructed to jump to a different instruction, the majority of software is written in high-level programming languages that are easier and more efficient for programmers, meaning closer to a natural language. High-level languages are translated into machine language using a compiler or an interpreter or a combination of the two, an outline for what would have been the first piece of software was written by Ada Lovelace in the 19th century, for the planned Analytical Engine. However, neither the Analytical Engine nor any software for it were ever created, the first theory about software—prior to creation of computers as we know them today—was proposed by Alan Turing in his 1935 essay Computable numbers with an application to the Entscheidungsproblem. This eventually led to the creation of the academic fields of computer science and software engineering. Computer science is more theoretical, whereas software engineering focuses on practical concerns.
However, prior to 1946, software as we now understand it—programs stored in the memory of stored-program digital computers—did not yet exist, the first electronic computing devices were instead rewired in order to reprogram them. On virtually all platforms, software can be grouped into a few broad categories. There are many different types of software, because the range of tasks that can be performed with a modern computer is so large—see list of software. System software includes, Operating systems, which are collections of software that manage resources and provides common services for other software that runs on top of them. Supervisory programs, boot loaders and window systems are parts of operating systems. In practice, an operating system bundled with additional software so that a user can potentially do some work with a computer that only has an operating system. Device drivers, which operate or control a particular type of device that is attached to a computer, which are computer programs designed to assist users in the maintenance and care of their computers
Electronic mail, or email, is a method of exchanging digital messages between people using digital devices such as computers and mobile phones. Email first entered use in the 1960s and by the mid-1970s had taken the form now recognized as email. Email operates across computer networks, which today is primarily the Internet, some early email systems required the author and the recipient to both be online at the same time, in common with instant messaging. Todays email systems are based on a store-and-forward model, Email servers accept, forward and store messages. Originally an ASCII text-only communications medium, Internet email was extended by Multipurpose Internet Mail Extensions to carry text in character sets. International email, with internationalized email addresses using UTF-8, has been standardized, the history of modern Internet email services reaches back to the early ARPANET, with standards for encoding email messages published as early as 1973. An email message sent in the early 1970s looks very similar to an email sent today.
Email played an important part in creating the Internet, and the conversion from ARPANET to the Internet in the early 1980s produced the core of the current services, the term electronic mail was used generically for any electronic document transmission. For example, several writers in the early 1970s used the term to describe fax document transmission, as a result, it is difficult to find the first citation for the use of the term with the more specific meaning it has today. This spelling appears in most dictionaries, Mail was the form used in the original protocol standard, RFC524. The service is referred to as mail, and a piece of electronic mail is called a message. EMail is a form that has been used in RFCs for the Authors Address and is expressly required for historical reasons. E-mail is sometimes used, capitalizing the initial E as in similar abbreviations like E-piano, E-guitar, A-bomb, by 1968, AUTODIN linked more than 300 sites in several countries. With the introduction of MITs Compatible Time-Sharing System in 1961, multiple users could log in to a system from remote dial-up terminals.
Informal methods of using this to pass messages were developed and expanded,1965 – MITs CTSS MAIL and it used the Unix mail client to send messages between system users. The concept was extended to communicate remotely over the Berkeley Network,1979 – EMAIL, an application written by Shiva Ayyadurai for the University of Medicine and Dentistry of New Jersey. 1979 – MH Message Handling System developed at RAND provided several tools for managing electronic mail on Unix, most of them only allowed communication between users logged into the same host or mainframe, although there might be hundreds or thousands of users within an organization. In the early 1980s, networked personal computers on LANs became increasingly important, server-based systems similar to the earlier mainframe systems were developed
Integrated Authority File
The Integrated Authority File or GND is an international authority file for the organisation of personal names, subject headings and corporate bodies from catalogues. It is used mainly for documentation in libraries and increasingly by archives, the GND is managed by the German National Library in cooperation with various regional library networks in German-speaking Europe and other partners. The GND falls under the Creative Commons Zero license, the GND specification provides a hierarchy of high-level entities and sub-classes, useful in library classification, and an approach to unambiguous identification of single elements. It comprises an ontology intended for knowledge representation in the semantic web, available in the RDF format
Electronic spamming is the use of electronic messaging systems to send an unsolicited message, especially advertising, as well as sending messages repeatedly on the same site. It is named after Spam, a meat, by way of a Monty Python sketch about a menu that includes Spam in every dish. The food is stereotypically disliked/unwanted, so the word came to be transferred by analogy, because the barrier to entry is so low, spammers are numerous, and the volume of unsolicited mail has become very high. In the year 2011, the figure for spam messages is around seven trillion. The costs, such as lost productivity and fraud, are borne by the public and by Internet service providers, Spamming has been the subject of legislation in many jurisdictions. A person who creates electronic spam is called a spammer, the term spam is derived from the 1970 Spam sketch of the BBC television comedy series Monty Pythons Flying Circus. The sketch is set in a cafe where nearly every item on the menu includes Spam canned luncheon meat, as the waiter recites the Spam-filled menu, a chorus of Viking patrons drowns out all conversations with a song repeating Spam, Spam, Spam… Spammity Spam.
In the 1980s the term was adopted to describe certain abusive users who frequented BBSs and MUDs, in early chat rooms services like PeopleLink and the early days of Online America, they actually flooded the screen with quotes from the Monty Python Spam sketch. Sending an irritating, meaningless block of text in this way was called spamming and this was used as a tactic by insiders of a group that wanted to drive newcomers out of the room so the usual conversation could continue. It was used to prevent members of groups from chatting—for instance, Star Wars fans often invaded Star Trek chat rooms. This act, previously called flooding or trashing, known as spamming. The term was applied to a large amount of text broadcast by many users. It came to be used on Usenet to mean excessive multiple posting—the repeated posting of the same message, the unwanted message would appear in many, if not all newsgroups, just as Spam appeared in nearly all the menu items in the Monty Python sketch. This use had become established—to spam Usenet was flooding newsgroups with junk messages, the word was attributed to the flood of Make Money Fast messages that clogged many newsgroups during the 1990s.
There was an effort to differentiate between types of newsgroup spam, Messages that were crossposted to too many newsgroups at once – as opposed to those that were posted too frequently – were called velveeta. In the late 19th Century Western Union allowed telegraphic messages on its network to be sent to multiple destinations, the first recorded instance of a mass unsolicited commercial telegram is from May 1864, when some British politicians received an unsolicited telegram advertising a dentistry shop. The earliest documented spam was a message advertising the availability of a new model of Digital Equipment Corporation computers sent by Gary Thuerk to 393 recipients on ARPANET in 1978. Rather than send a message to each person, which was the standard practice at the time, he had an assistant, Carl Gartley
Simple Mail Transfer Protocol
Simple Mail Transfer Protocol is an Internet standard for electronic mail transmission. First defined by RFC821 in 1982, it was last updated in 2008 with Extended SMTP additions by RFC5321, for retrieving messages, client applications usually use either IMAP or POP3. SMTP communication between mail servers uses TCP port 25, Mail clients on the other hand, often submit the outgoing emails to a mail server on port 587. Despite being deprecated, mail providers sometimes still permit the use of nonstandard port 465 for this purpose, SMTP connections secured by SSL, known as SMTPS, can be made using STARTTLS. Various forms of electronic messaging were used in the 1960s. People communicated with one another using systems developed for specific mainframe computers, as more computers were interconnected, especially in the US Governments ARPANET, standards were developed to allow users of different systems to email one another. SMTP grew out of these standards developed during the 1970s, fewer than 50 hosts were connected to the ARPANET at this time.
Further implementations include FTP Mail and Mail Protocol, both from 1973, development work continued throughout the 1970s, until the ARPANET transitioned into the modern Internet around 1980. Jon Postel proposed a Mail Transfer Protocol in 1980 that began to remove the reliance on FTP. SMTP was published as RFC788 in November 1981, by Postel, the SMTP standard was developed around the same time as Usenet, a one-to-many communication network with some similarities. SMTP became widely used in the early 1980s, at the time, it was a complement to Unix to Unix Copy Program mail, which was better suited for handling email transfers between machines that were intermittently connected. SMTP, on the hand, works best when both the sending and receiving machines are connected to the network all the time. Both use a store and forward mechanism and are examples of push technology, though Usenets newsgroups are still propagated with UUCP between servers, UUCP as a mail transport has virtually disappeared along with the bang paths it used as message routing headers.
Sendmail, released with 4. 1cBSD, right after RFC788, was one of the first mail transfer agents to implement SMTP, over time, as BSD Unix became the most popular operating system on the Internet, sendmail became the most common MTA. Some other popular SMTP server programs include Postfix, Novell GroupWise, Novell NetMail, Microsoft Exchange Server, Message submission and SMTP-AUTH were introduced in 1998 and 1999, both describing new trends in email delivery. Originally, SMTP servers were typically internal to an organization, receiving mail for the organization from the outside and this behavior is helpful when the message being fixed is an initial submission, but dangerous and harmful when the message originated elsewhere and is being relayed. Cleanly separating mail into submission and relay was seen as a way to permit, as spam became more prevalent, it was seen as a way to provide authorization for mail being sent out from an organization, as well as traceability. This separation of relay and submission quickly became a foundation for modern email security practices, as this protocol started out purely ASCII text-based, it did not deal well with binary files, or characters in many non-English languages
In Internet, an email client, email reader or more formally mail user agent is a computer program in the category of groupware environments used to access and manage a users email. Client is meant to be a role, for example, a web application which provides message management and reception functions may internally act as an email client, as a whole, it is commonly referred to as webmail. Likewise, email client may be referred to a piece of hardware or software whose primary or most visible role is to work as an email client. Like most client programs, a client is only active when a user runs it. The most common arrangement is for a user to make an arrangement with a remote Mail Transfer Agent server for the receipt. The MTA, using a mail delivery agent, adds email messages to a clients storage as they arrive. The remote mail storage is referred to as the users mailbox, the default setting on many Unix systems is for the mail server to store formatted messages in mbox, within the users HOME directory.
Of course, users of the system can log-in and run a mail client on the computer that hosts their mailboxes, in which case. A users mailbox can be accessed in two dedicated ways, the Post Office Protocol allows the user to download messages one at a time and only deletes them from the server after they have been successfully saved on local storage. It is possible to leave messages on the server to another client to access them. However, there is no provision for flagging a specific message as seen, answered, or forwarded, the Internet Message Access Protocol allows users to keep messages on the server, flagging them as appropriate. IMAP provides folders and sub-folders, which can be shared among different users with different access rights. Typically, the Sent and Trash folders are created by default, IMAP features an idle extension for real time updates, providing faster notification than polling, where long lasting connections are feasible. See the remote messages section below, in addition, the mailbox storage can be accessed directly by programs running on the server or via shared disks.
Direct access can be efficient but is less portable as it depends on the mailbox format, it is used by some email clients. Email clients usually contain user interfaces to display and edit text, some applications permit the use of a program-external editor. The email clients will perform formatting according to RFC5322 for headers and body, to better assist the user with destination fields, many clients maintain one or more address books and/or are able to connect to an LDAP directory server. For originator fields, clients may support different identities, client settings require the users real name and email address for each users identity, and possibly a list of LDAP servers