(1) URL: –

A Uniform Resource Locator (URL), commonly informally termed a web address (which term is not defined identically) is a reference to a web resourcethat specifies its location on a computer network and a mechanism for retrieving it. A URL is a specific type of Uniform Resource Identifier (URI), although many people use the two terms interchangeably. A URL implies the means to access an indicated resource, which is not true of every URI. URLs occur most commonly to reference web pages (http), but are also used for file transfer (ftp), email (mailto), database access (JDBC), and many other applications.

(2) Email address: –

Electronic mail is a method of exchanging digital messages between computer users; such messaging first entered substantial use in the 1960s and by the 1970s had taken the form now recognized as email. Email operates across computer networks, now primarily the Internet.

Some early email systems required the author and the recipient to both is online at the same time, in common with instant messaging. Today’s email systems are based on a store-and-forward model. Email servers accept, forward, deliver, and store messages. Neither the users nor their computers are required to be online simultaneously; they need connect only briefly, typically to a mail server, for as long as it takes to send or receive messages.

(3) Internet versus intranet: –

There’s one major distinction between an intranet and the Internet: The Internet is an open, public space, while an intranet is designed to be a private space. An intranet may be accessible from the Internet, but as a rule it’s protected by a password and accessible only to employees or other authorized users.

From within a company, an intranet server may respond much more quickly than a typical Web site. This is because the public Internet is at the mercy of traffic spikes, server breakdowns and other problems that may slow the network. Within a company, however, users have much more bandwidth and network hardware may be more reliable. This makes it easier to serve high-bandwidth content, such as audio and video, over an intranet.

(4) ISP: –

Short for Internet Service Provider, it refers to a company that provides Internet services, including personal and business access to the Internet. For a monthly fee, the service provider usually provides a software package, username, passwordand access phone number. Equipped with a modem, you can then log on to the Internet and browse the World Wide Web and USENET, and send and receive e-mail. For broadband access you typically receive the broadband modem hardware or pay a monthly fee for this equipment that is added to your ISP account billing.

In addition to serving individuals, ISPs also serve large companies, providing a direct connection from the company’s networks to the Internet. ISPs themselves are connected to one another through Network Access Points (NAPs). ISPs may also be called IAPs (Internet Access Providers).

(5) NIC: –

In the early days of computing, individual computers operated as stand-alone systems. The earliest personal computers did not have an easy way to connect to other computers. In order to transfer files between computers, you had to use a portable storage medium such as a floppy disk; however, in modern-day computers, connecting to a network is essential. For example, you need to connect to use e-mail, access information on the Internet, and share documents within a corporate network.

A computer uses a network interface card (NIC) to become part of a network. The NIC contains the electronic circuitry required to communicate using a wired connection (e.g., Ethernet) or a wireless connection (e.g., Wi-Fi). A network interface card is also known as a network interface controller, network adapter, or Local Area Network (LAN) adapter.

Early NICs typically consisted of an expansion card connected to a computer’s motherboard. This separate card contained the electronic circuitry and the physical connectors. Here’s an example of a typical NIC.

(6) Bridge: –

In telecommunication networks, a bridge is a product that connects a local area network (LAN) to another local area network that uses the same protocol(for example, Ethernet or token ring). You can envision a bridge as being a device that decides whether a message from you to someone else is going to the local area network in your building or to someone on the local area network in the building across the street. A bridge examines each message on a LAN, “passing” those known to be within the same LAN, and forwarding those known to be on the other interconnected LAN (or LANs).

In bridging networks, computer or node addresses have no specific relationship to location. For this reason, messages are sent out to every address on the network and accepted only by the intended destination node. Bridges learn which addresses are on which network and develop a learning table so that subsequent messages can be forwarded to the right network.

(7) Router: –

A router is hardwaredevice designed to receive, analyze and move incoming packets to another network. It may also be used to convert the packets to another network interface, drop them, and perform other actions relating to a network. The picture shows the Linksys BEFSR11 wireless router and is what many home routers resemble.

A router has a lot more capabilities than other network devices, such as a hub or a switch that are only able to perform basic network functions. For example, a hub is often used to transfer data between computers or network devices, but does not analyze or do anything with the data it is transferring. By contrast, routers can analyze the data being sent over a network, change how it is packaged, and send it to another network or over a different network. For example, routers are commonly used in home networks to share a single Internet connection between multiple computers.

(8) Encoder: –

An encoder is the combinational circuit which performs a reverse function that of decoder. Encode inputs are decimal digits and/or alphabetic characters and outputs are coded representation of these inputs.

(9) Decoder: –

The basic function of a decoder is to detect the presence of a specified combination of bits on its inputs and to indicate that presence by a specified output level. A decoder has n input lines o handles n bits and from one to 2noutput lines to indicate the presence of one or more n – bit combinations.


(1) String: –

Strings are actually one-dimensional array of characters terminated by a null character ‘\0’. Thus a null-terminated string contains the characters that comprise the string followed by a null.

The following declaration and initialization create a string consisting of the word “Hello”. To hold the null character at the end of the array, the size of the character array containing the string is one more than the number of characters in the word “Hello.”

(2) Dynamic memory allocation: –

When we declare an array, we need to reserve some memory to store the elements of this array.  This memory allocation and it is static. That is when we declare an array, we specify the number of elements in that array and a fixed memory is allocated.  Once declared the size of the array cannot be changed.

But there are situations in which we may want to declare the variable and not allocate memory for it until we use that variable.  We may also want to free the memory allocated for a variable after its use is over. These are some of the things we will concentrate on in this lecture.

The dynamic allocation of memory during the program execution is achieved through two built in functions malloc or calloc, realloc and free. There is also sizeof() function used to determine the number of bytes occupied by an entity in memory.

(3) File handling function: –

Files are constructed on storage device such as on disk or on tap. C compiler provides facility to handle file where file mean to operate data file.

Normally we input data for a program using keyboard. And computer will display output on screen these input and output devices called I/O (Input Output) console. Data file operate from storage device. There is some difference between I/O console and I/O storage device are (1) The console always exist but I/O file may or may not be exist. (2) In case of a console, the program reads from the keyboard and writes on to the screen. In case of file, it is possible to read data and to write data to some specific file which is located in the storage device (3) Before reading or writing data from a file, it must be open by user and after processing of data, I/O file must be close by the user but it is not necessary to console input output.

(4) Preprocessor directive: –

The C Preprocessor is not a part of the compiler, but is a separate step in the compilation process. In simple terms, a C Preprocessor is just a text substitution tool and it instructs the compiler to do require pre-processing before the actual compilation. We’ll refer to the C Preprocessor as CPP.

All preprocessor commands begin with a hash symbol (#). It must be the first nonblank character, and for readability, a preprocessor directive should begin in the first column.

(5) Structure & Union: –

Structure in c is a heterogeneous user defined data type it is also called abstract data type. Structure in c is similar to record in Pascal. A structure may contain different data type inside structure, variable are called member. It groups multiple variables in a single entity.

An union is a data type in c which allows the over lay of more than one variable in the same memory area normally. Every variable is stored in a separate location and as a result each of those variable have than on address often, it is found that some variable used in the program are used only a small portion of the source code.

(6) Switch statement: –

A switch statement allows a variable to be tested for equality against a list of values. Each value is called a case, and the variable being switched on is checked for each switch case.