Internet Dictionary
Click on a letter to see the relevant terms: A B C D E F G H I J K L M N O P Q R S T U V W Z

RAM Random Access Memory. Usually, when someone refers to a computer's memory, he or she is talking about the computer's RAM. This is a very fast read-write memory, equivalent to a group of addressable registers. After supplying an address, you can read the stored byte or write a new byte into the addressed location. If your computer has 16 Mbytes of RAM, it means it has approximately 16 million addressable memory locations each able to store one byte. The RAM in a PC is volatile, meaning that the contents of the memory are lost when the power is turned off. When you turn the power on, the boot sector on the computer's hard disk is loaded into the RAM. This short bit of code then loads the operating system into the RAM and the computer can function normally. When you click on a link to any web page, some remote server will download the web page into your RAM. After a web page is in the RAM, you can quickly move through the page by scrolling or linking to bookmarks on the same page. The delays you experience when surfing the Web are caused by waiting for a remote server to download a new web page into your RAM.

Real audio Instead of downloading an audio file and then playing it, real audio plays directly through the browser. It's analogous to Java interpretation and execution of each line of a program, except that it's an audio stream being played while downloaded into your PC's memory.

Register A register is a string of binary devices, each able to store one bit. For instance, one way to make an 8-bit register is with 8 transistors that are either in saturation (on) or in cutoff (off). If "on" represents 1 and "off" represents 0, the register can store one byte of data. As an example, if the transistors are on-on-off-off-on-off-on-on, then the stored byte is 11001011. An 8-bit register can store any byte from 00000000 to 11111111, equivalent to decimal 0 through 255. A 16-bit register can store 16 bits, equivalent to decimal 0 through 65535. A 32-bit register can store 32 bits, equivalent to decimal 0 through 4,294,967,295. Early PCs used 8-bit registers. The newest PCs are using 32-bit registers.

Resources Networked computers share three things: data files, programs, and resources. Data files can be copied from one computer's hard disk to another. Programs usually remain on the source computer but can be used by a client that downloads the program into its RAM. Resources refer to printers, hard drives, CD-ROM drives, modems, etc. The most common example of a shared resource is a laser printer connected to a computer, but available for printing by other computers in the network.

Ring network A network of computers using ring topology.

Ring topology The physical shape of a ring network. For instance, draw a circle on a piece of paper. Draw 6 dots along the circle with spaces between the dots. This dotted circle represents six networked computers using ring topology. It has the advantage that a cable break between any two computers does not disable the network. Why? Because a cable break in a ring network changes it to a bus network, which still allows all computers to communicate. The two computers connected by the broken cable no longer communicate by the shortest route, but they still can communicate by the longest route, the opposite direction on the ring.

Root directory The directory that stores all web pages of the root web.

Root web When you enter a web site for the first time, you are entering the home page of the root web. The directory that this home page is stored in is called the root directory of the web site. Any page that is part of this root web is stored in the same root directory. Larger web sites need to use child webs, kind of like chapters in a book. If child webs are used, their pages will be stored in subdirectories of the root directory.

Router Pronounced "rooter". This is a computer that receives TCP/IP traffic from one network and sends it on to another network. A router reads the addresses of each packet and forwards it, usually to another router along the destination path. The transmission between routers is called a hop. In other words, TCP/IP data from your computer hops between several routers to its final destination.

RTT Round Trip Time. When you ping another computer on a TCP/IP network using "ping IP address", your PC sends a packet of data to the addressed computer, which sends back a reply packet. The round trip is the time that elapses from the instant your PC sends the packet and the instant it receives a reply. Round trip measures the delay of a network. The delay between two computers on a LAN is only a few milliseconds. On the Internet it's usually a couple hundred milliseconds.

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