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ASCII is an acronym for American Standard Code for Information Interchange, a widely used standard for encoding text documents on computers. Usually, a file described as "ASCII" does not contain any special embedded control characters; you can view the contents of the file, change it with an editor, or print it with a printer.

In ASCII, every letter, number, and punctuation symbol has a corresponding number, or ASCII code. For example, the character for the number 1 has the code 49, capital letter A has the code 65, and a blank space has the code 32. This encoding system not only lets a computer store a document as a series of numbers, but also lets it share such documents with other computers that use the ASCII system.

Documentation files or program source code files are usually stored as ASCII text. In contrast, binary files, such as executable programs, graphical images, or word processing documents, contain other characters that cannot be normally displayed or printed, and are usually illegible to human beings.

The format of a file, whether ASCII or binary, becomes important when you are transferring files between computers. For example, when using FTP, you can transfer ASCII text files without any special consideration. To exchange binary files, however, you may need to enter the command set binary or otherwise prepare the client to transfer binary files, so that the computer will correctly transmit the special characters in the file.

Note: Most current FTP software will automatically transfer ASCII and binary files correctly.

BIOS is an acronym for Basic Input/Output System. It is the boot firmware program on a PC, and controls the computer from the time you start it up until the operating system takes over. When you turn on a PC, the BIOS first conducts a basic hardware check, called a Power-On Self Test (POST), to determine whether all of the attachments are present and working. Then it loads the operating system into your computer's random access memory, or RAM.

The BIOS also manages data flow between the computer's operating system and attached devices such as the hard disk, video card, keyboard, mouse, and printer.

The BIOS stores the date, the time, and your system configuration information in a battery-powered, non-volatile memory chip, called a CMOS (Complementary Metal Oxide Semiconductor) after its manufacturing process.

Although the BIOS is standardized and should rarely require updating, some older BIOS chips may not accommodate new hardware devices. Before the early 1990s, you couldn't update the BIOS without removing and replacing its ROM chip. Contemporary BIOS resides on memory chips such as flash chips or EEPROM (Electrically Erasable Programmable Read-Only Memory), so that you can update the BIOS yourself if necessary.

For detailed information about BIOS updates, visit: http://www.wimsbios.com/index.jsp

A content management system (CMS) is a system used to manage the content of a Web site. Content management systems are deployed primarily for interactive use by a potentially large number of contributors.

The content managed includes computer files, image media, audio files, electronic documents and web content. The idea behind a CMS is to make these files available inter-office, as well as over the web. A Content Management System would most often be used as an archive as well. Many companies use a CMS to store files in a non-proprietary form. Companies use a CMS to share files with ease, as most systems use server-based software, even further broadening file availability. As shown below, many Content Management Systems include a feature for Web Content, and some have a feature for a "workflow process."

"Work flow" is the idea of moving an electronic document along for either approval, or for adding content. Some Content Management Systems will easily facilitate this process with email notification, and automated routing. This is ideally a collaborative creation of documents. A CMS facilitates the organization, control, and publication of a large body of documents and other content, such as images and multimedia resources.

What is DHCP?

Dynamic Host Configuration Protocol (DHCP) is a network protocol that enables a server to automatically assign an IP address to a computer from a defined range of numbers (i.e., a scope) configured for a given network.

DHCP assigns an IP address when a system is started, for example:

1. A user turns on a computer with a DHCP client.

2. The client computer sends a broadcast request (called a DISCOVER or DHCPDISCOVER), looking for a DHCP server to answer.

3. The router directs the DISCOVER packet to the correct DHCP server.

4. The server receives the DISCOVER packet. Based on availability and usage policies set on the server, the server determines an appropriate address (if any) to give to the client. The server then temporarily reserves that address for the client and sends back to the client an OFFER (or DHCPOFFER) packet, with that address information. The server also configures the client's DNS servers, WINS servers, NTP servers, and sometimes other services as well.

5.The client sends a REQUEST (or DHCPREQUEST) packet, letting the server know that it intends to use the address.

6.The server sends an ACK (or DHCPACK) packet, confirming that the client has a been given a lease on the address for a server-specified period of time.

When a computer uses a static IP address, it means that the computer is manually configured to use a specific IP address. One problem with static assignment, which can result from user error or inattention to detail, occurs when two computers are configured with the same IP address. This creates a conflict that results in loss of service. Using DHCP to dynamically assign IP addresses minimizes these conflicts.

The term domain can refer either to a local subnetwork or to descriptors for sites on the Internet (e.g., www.sahoster.com).

Local subnetwork domains
On a local area network (LAN), a domain is a subnetwork made up of a group of clients and servers under the control of one central security database. Within a domain, users authenticate once to a centralized server known as a domain controller, rather than repeatedly authenticating to individual servers and services. Within a domain, individual servers and services accept the user based on the approval of the domain controller.

Internet domains
On the Internet, a domain is part of every network address. All devices sharing a common part of an address, or URL, are said to be in the same domain. In the address www.sahoster.com/people/address.shtml, sahoster is the domain, people is a directory in that domain, and address.shtml is a file in the directory.

To obtain a domain, you must purchase it from a domain registrar. You can choose a registrar from the list of accredited registrars.

Internet domains are organized by level. Most people are familiar with the Top Level Domains (TLDs) of .com, .edu, .net, and .org. TLDs are the most general and basic part of the URL. There are actually many top level domains. Every country is assigned one; see the complete list of country code Top Level Domains (ccTLDs).

Category domains called generic TLDs (gTLDs) are also available. These domains are described on the Internet Assigned Numbers Authority gTLD page.

The governing body for domain names is called ICANN (Internet Corporation For Assigned Names and Numbers), a non-profit corporation charged with overseeing the creation and distribution of TLDs.

A driver is software that allows your computer to communicate with hardware or devices. Without drivers, the hardware you connect to your computer (for example, a video card or a webcam) will not work properly.

A firewall is a system designed to prevent unauthorized access to or from a private network. You can implement a firewall in either hardware or software form, or a combination of both. Firewalls prevent unauthorized Internet users from accessing private networks connected to the Internet, especially intranets. All messages entering or leaving the intranet (i.e., the local network to which you are connected) must pass through the firewall, which examines each message and blocks those that do not meet the specified security criteria.

There are several types of firewall techniques:

Packet filtering: The system examines each packet entering or leaving the network and accepts or rejects it based on user-defined rules. Packet filtering is fairly effective and transparent to users, but it is difficult to configure. In addition, it is susceptible to IP spoofing.

Circuit-level gateway implementation: This process applies security mechanisms when a TCP or UDP connection is established. Once the connection has been made, packets can flow between the hosts without further checking.

Acting as a proxy server: A proxy server is a type of gateway that hides the true network address of the computer(s) connecting through it. A proxy server connects to the Internet, makes the requests for pages, connections to servers, etc., and receives the data on behalf of the computer(s) behind it. The firewalling capabilities lie in the fact that a proxy can be configured to only allow certain types of traffic (e.g., HTTP files, or web pages) through. A proxy server has the potential drawback of slowing network performance, since it has to actively analyze and manipulate traffic passing through it.
For more information, refer to the Knowledge Base document What is a proxy server?

In practice, many firewalls use two or more of these techniques in concert.

A firewall is considered a first line of defense in protecting private information. It cannot be considered the only line, however, since firewalls are mostly designed to protect network traffic and connections, and therefore do not attempt to authenticate users (i.e., determine who is and who isn't allowed to use the computer the firewall is protecting, or see the traffic coming to it).

The most common of free software firewalls for Windows is the one built into Windows XP. Windows 2000 had packet filtering abilities, but it wasn't a true firewall; it was not intended to block traffic and protect the computer, but rather to classify certain packets and treat them differently. Earlier versions of Windows did not have firewalls built in at all.

Macintosh computers running Mac OS X 10.2 and later are also equipped with a built-in firewall.

Third-party packages exist, such as Zone Alarm, Norton Personal Firewall, Tiny, Black Ice Protection, and McAfee Personal Firewall. Many offer free versions, or at least free trials of their commercial versions.

Many home and small office broadband routers have at least rudimentary firewalling capabilities built in. These tend to be simply port/protocol filters, although models with much finer control are available.

FTP is an acronym for File Transfer Protocol. As the name suggests, FTP is used to transfer files between computers on a network, such as the Internet. You can use FTP to exchange files between computer accounts, to transfer files between an account and a desktop computer, or to access software archives on the Internet. Keep in mind, however, that many FTP sites are heavily used and require several attempts before connecting.

Note: You need to use a client that supports secure FTP (e.g., SSH Secure Shell for Windows or MacSFTP for Macintosh) to transfer files to and from Indiana University's central systems. For more, see What is SFTP, and how do I use it?

How to use FTP
Graphical FTP clients
Using graphical FTP clients simplifies file transfers by allowing you to drag and drop file icons between windows. When you open the program, enter the name of the FTP host (e.g., ftp.empire.gov) and your username and password. If you are logging into an anonymous FTP server, you may not have to enter anything. Two common FTP programs are Transmit (for Macintosh) and Hummingbird FTP (for Windows).

Web browser
You can use a web browser to connect to FTP addresses exactly as you would to connect to HTTP addresses. Using a web browser for FTP transfers makes it easy for you to browse large directories and read and retrieve files. Your web browser will also take care of some of the details of connecting to a site and transferring files. While this method is convenient, web browsers are often slower and less reliable and have fewer features than dedicated FTP clients.

Command line FTP
You can also use FTP in a command line format from your Unix account, or your Unix or Windows workstation. For help, see What are some common FTP commands? For example, to start FTP, at the command line prompt, enter: ftp ftp.empire.gov
If you are connecting to your own account, enter your username and password. If you are connecting to an anonymous FTP site, for your username, enter anonymous . For your password, enter your email address.

Keeping track of files
Even if you are using a desktop computer to log into a Unix shell account, the files you transfer in an FTP session started from your Unix shell account will be stored in the directory of your account, not on the hard drive of your desktop computer.

If you make an Ethernet, broadband, or dial-up connection and run an FTP program (e.g., Transmit or Hummingbird) from your desktop computer, the files will usually transfer to your hard drive.

Anonymous FTP
Many universities, government agencies, companies, and private individuals have set up publicly accessible archives on the Internet. There are thousands of these sites that contain a myriad of programs, data files, and informational text. At these sites, public directories and files that may be read by the rest of the world via FTP are set aside. These directories are usually named /pub. You can usually find specific directions and information about the site in greeting messages or in files with names like README.

Remember that anonymous FTP is a privilege granted by the organization that owns the computer to which you are connecting.

Some general guidelines for using anonymous FTP are:
- Don't transfer files you don't need.
- Don't transfer an excessive amount of material.
- Restrict your transfers to off-peak hours, if possible.