Usually wireless adapters can be connected to computers not to modems.
Yes, they can. There are plenty adapters for USB ports as well as PCI, PCIe.
In most case, no they do not.
Nowadays most of computers come with wireless adapters but it is an extra option and you need to pay for it. You always can check presence of wireless adapter by going to Device Manager->Network adapters.
Actually they do, of course it depends on brand. But majority of adapters serve as long as computers.
The best place find some wireless adapters is at any store that sells computers. You can also go online to EBay and find some new and used ones, with a good return policy.
Wireless network adapters (also known as wireless NICs or wireless network cards) are required for each device on a wireless network. Some newer laptop computers incorporate wireless adapters as a built-in feature of the system. Separate add-on adapters must be purchased for most computers, however. Popular wireless network adapters for PCs exist in the form of a PCMCIA "credit card." Macintosh computers use the distinctive AirPort card. USB wireless adapters that do not resemble cards also exist. Strictly speaking, no wireless hardware other than adapters is required to build a small wireless LAN (WLAN). However, to increase the performance of a WLAN, accommodate more computers, and increase the network's range, wireless access points and/or wireless routers can be deployed. Wireless routers function comparably to traditional routers for wired networks. One generally deploys wireless routers when building an all-wireless network from the ground up. An alternative to routers, access points allow wireless networks to join an existing wired network. One typically deploys access points when growing a network that already has a wired switch or router installed. In home networking, a single access point (or router) possesses sufficient range to span most homes. Businesses in office buildings often must deploy multiple access points and/or routers. Access points and routers often utilize a wireless antenna that significantly increase the communication range of the wireless radio signal. These antennas are optional and removable on most equipment. It's also possible to mount antennas on wireless clients to increase the range of wireless adapters. This is common practice for wardrivers, but add-on antennas are generally not required in typical home or business networks.
PCMCIA wireless adapter and USB wireless adapters. PCMCIA goes into notebooks (outdated one)
The needed devices are wireless access point (WAP), a wireless router. You need computers with wireless networking adapters. And you need a "wired" connection to the internet for the router to plug into. Most people are able to install it themselves but your ISP will install it if you are more comfortable with that.
The Wireless adapters should not be required for computers because they are not mobile and have better connection with the Ethernet. Netgear is the most popular type of adapter and is recommended only for laptops.
A wireless router allows you to create a wireless internet system for your home. This enables you to have multiple computers connect to the internet in multiple locations, giving you the freedom to use the internet anywhere in your house. A wireless router allows you to create a wireless internet system for your home. This makes it possible for you to have multiple computers to have the internet in multiple locations, allowing the freedom to use the internet anywhere in your house.
There are many USB wireless adapters on the market today. Some of the top rated USB wireless adapters include the Cisco Linksys, Link Xtreme, Belkin Wireless N+, and TRENDNet.