Tape types
For almost as long as computers have existed, magnetic tape has been the backup medium of choice. Tape is inexpensive, well understood and easy to remove and replace.
Stories by Russell Kay
Data models
In the real world, we think of data as facts, figures and other bits of knowledge. Put a lot of data items together in a useful form, and you get information -- maybe even intelligence.
Presence Technology
Presence technology allows a network user to know when another user is connected to the network and thus available to receive and immediately answer a communication. Instant messaging, pioneered by America Online, is the first and best-known example of a presence technology.
Direct access file system
The Direct Access File System (DAFS) is a developing protocol for storing and accessing files. Under DAFS, data is transferred directly from storage to client as logical files, not physical storage blocks. DAFS improves performance significantly because the request and its fulfillment bypass the server kernel and go directly to the file system.
SNMP
Simple Network Management Protocol (SNMP) is the standard way of checking that devices on a network are operating properly. With SNMP, devices on the network monitor their own activity, using built-in software called an agent, and store that information in a database called a management information base (MIB). An overall management program, such as NetView or OpenView, sends messages to the various agents on the network, which respond by sending back the MIB data.
UDDI: Looking up Web services
Organizations that attempt to do business online quickly learn that there are lots of IT-related problems that others have already solved. Increasingly, those solutions are becoming readily available to anyone, in the form of Web services. Web services are perhaps the latest, most powerful example of reusable program components, the difference being that instead of incorporating component code directly into your application, you simply access the service over the Web, pass your parameters along to it and let the remote service do the work for you.
UDDI: Looking Up Web Services
Universal Description, Discovery and Integration (UDDI) is akin to an Internet phone book that describes businesses and the Web services each supports. It's an XML-based, platform-independent, Internet-accessible registry in which businesses, software vendors and programmers can describe the Web services they offer and provide links on how to use them.
It's the Law!
Almost as long as there have been computers, IT pros have formulated "laws" - serious ones, like Moore's Law, and otherwise - to describe the conditions that govern computing.
Web caching
Web caching is the practice of storing frequently requested -- but infrequently changed -- pages, images and other Web objects on a nearby server or even a user's PC.
Wireless security
Wireless security requires a number of technical safeguards to protect the confidentiality and integrity of e-mail and other data broadcast over radio waves.
Wireless security
Some people think that the term wireless security is an oxymoron, but in fact, wireless security isn't very different from wired security. To protect data going out from an organization, whether over radio waves that anyone can listen in on or over phone lines or network cabling that can be wiretapped or sniffed, you need the same basic controls as with any other connection.
High-speed serial ports
Universal Serial Bus (USB) is a modern standard for connecting peripheral devices to a computer using a single connector that replaces serial, parallel and network connections. USB delivers both power and data, and up to 127 USB devices can be daisy-chained together. USB 1.1 operates at up to 12M bit/sec., while USB 2.0 delivers up to 480M bit/sec. IEEE 1394, a competing technology (also called FireWire and iLink), delivers 400M bit/sec.
System Development Life Cycle
Once upon a time, software development consisted of a programmer writing code to solve a problem or automate a procedure. Nowadays, systems are so big and complex that teams of architects, analysts, programmers, testers and users must work together to create the millions of lines of custom-written code that drive our enterprises.
FireWire
Before USB, the primary high-speed serial connection was that defined by IEEE standard 1394 - better known by the name Apple Computer Corp. gave it, FireWire. (Sony and others call it iLink.)
Random Numbers
A random number can't be predicted in advance. Thus, we can define only what a random number is not, not what it is. Random numbers can be produced by physical processes, such as throwing a die, flipping a coin or counting intervals between radioactive decay events. By itself, software can't generate truly random numbers; instead, it creates what are called pseudorandom numbers, starting from a single random "seed."