The Domain Name System is one way to resolve host names in a TCP/IP environment. In non-Microsoft environments, host names are typically resolved through host files or DNS. In a Microsoft environment, WINS and broadcasts are also used. DNS is the primary system used to resolve host names on the Internet. In fact, DNS had its beginning in the early days of the Internet.In its early days, the Internet was a small network established by the Department of Defense for research purposes. This network linked computers at several government agencies with a few universities. The host names of the computers in this network were registered in a single HOSTS file located on a centrally administered server. Each site that needed to resolve host names downloaded this file. Few computers were being added to this network, so the HOSTS file wasn’t updated too often and the different sites only had to download this file periodically to update their own copies.

You will create two main types of variables in your PHP code: scalar and array. Scalar variables contain only one value at a time, and arrays contain a list of values, or even another array.The example at the beginning of this chapter created a scalar variable, and the code in this book deals primarily with scalar variables. You can find information on arrays in Appendix B, "Basic PHP Language Reference." When you assign a value to a variable, you usually assign a value of one of the following types:

Whether it’s because you have made a call using a mobile phone, received a message on your pager, checked your email from a PDA or even just seen an advert related to it, we have all come across a wireless data or voice network!If a user, application or company wishes to make data portable, mobile and accessible then wireless networking is the answer. A wireless networking system would rid of the downtime you would normally have in a wired network due to cable problems. It would also save time and money due to the fact that you would spare the expense of installing a lot of cables. Also, if a client computer needs to relocate to another part of the office then all you need to do is move the machine with the wireless network card.

Just because Linux is distributed for free, it doesn’t mean the software is not copyrighted. Linux has been registered as copyrighted under the GNU General Public License (GPL), which is known in the programming community as a copyleft instead of copyright because of its nature. The GPL allows you to redistribute the Linux software, along with the complete source code, to anyone who wants it. However, the original owner of the components retains the copyrights to the software.