Disks: For long-term storage, most computers have a disk drive. There are two types of disk drives. A removable disk drive contains a diskette (called a floppy) and allows the user to remove the diskette and store it somewhere else or use it in another computer (usually named A: or B:). An internal (or "hard") disk is permanently attached to the computer (usually named C: or D:). The hard disk can typically hold a lot more data and, since it is built into the computer, allows for faster access to the data.
Computer Networks: Computers can access information from the disks of other computers if they are physically connected. From one computer's point of view, the other computer's disks are just like its own. For example, the PC's in the ESU PC lab are physically connected to one disk ESU has decided to call the I: disk. There is not one separate I: disk in each computer. Rather, all of the I: drive files reside in another computer somewhere on campus.
Modems: Another way to connect computers is through a telephone line. Special programs and equipment (modems) are used to "dial," "answer" and "talk" between the computers. The speed of the data transfer through the telephone depends upon the telephone line and the modem but is usually much slower than if the two computers were physically connected.
Dedicated Lines: Many computers are connected via lines dedicated purely for computer communication. Such lines are on campus (e.g., so a computer in Stroud can talk to computer in Gessner) as well as throughout the world (e.g., so a computer in Stroud can talk to a computer in France). These dedicated lines make up what is called the internet. For most distances, these lines are much faster than the telephone lines. Each computer is assigned a unique computer address that allows the computers to find each other.
Most PC's don't require a password to access its own hard drive or removable drives. The common I: drive at ESU is set up so that you don't need a password to access that either. However, there are other computers on campus that need to be secure. Access to those require a password.
E-mail: An example of a computer that requires a password is the one that handles electronic mail (e-mail). Each ESU student is provided with a username and password that allows them access to only his/her information. To access the computer, you must provide your username and password. This computer is separate from the PC's in the PC lab. To access it, your computer must be connected to the e-mail computer. Most of the computers on campus are already connected via a dedicated line. If you are off campus, you must telephone in via a modem.
Telnet: If you are on campus, you can access the e-mail computer via a protocol called telnet, which allows you to communicate with the computer. You can also use telnet to access any computer connected to the internet (as long as you have an account on the other computer).
ftp: When you connect with another computer via telnet (i.e., "log in"), what you see on your screen is typically the same that you would see if you were actually there. If all you need to do is transfer files and information, "ftp" (file transfer protocol) is much simpler. You connect in a similar way (an account is needed) but there are no fancy graphics. You just tell the computer what files you want to get and it transfers them to your computer disk.
gopher: The problem with ftp and telnet is that the computers are exchanging information even if you are not really doing anything. This can slow down the transfer of information for the other computers who are trying to use the same line. Gopher was created to remedy this situation. With gopher, you are only connected when transfering the file. When you first connect to the other computer (which has special programs to handle these requests; usually a special part of the computer is made available to everyone so no password is required), a special file is automatically sent to your machine and then the connection is broken. This special file lists the files that are available on the machine. Once you choose the file you want, the connection is then automatically made again, the selected file is transfered, and then the connection is broken again. In this way, you are only connected during the transfer time.
http: To make the navigation through the internet easier, http was created (hyper-text transfer protocol). The http programs (browsers) work like gopher but allow for the transfered files to be seen (rather than just transfered to the disk). When the transfered files are written in a language called HTML (hypertext markup language), the list of files that are available on the machine can be seen as hyperlinks, where a simple click on the file name will then transfer the selected file. Like gopher, you are only connected during the time needed to transfer the file to your machine.
To use the browser to connect to another machine, you specify the file you want via its URL (uniform resource locator). For example, the URL of ESU's main file (home page) is http://www.esu.edu/index.shtml. The http:// specifies that the file should be transfered using the hypertext transfer protocol. The www.esu.edu/ is the address for the ESU computer. The index.shtml is the file that will be transfered (note: when the filename is index.shtml or index.html, it isn't necessary to specify it; thus, http://www.esu.edu/ would be sufficient in this case).
To access files through the browser, you can either (a) specify the URL directly, (b) click on the hypertext "links", or (c) use a "search engine".
Last updated: 27 September 1998.
bbq@esu.edu