Introduction: Telephone Applications
Android began as a platform for cellular telephone handsets, so it is no surprise that Android Apps are very capable of dealing with the phone. You can write apps that dial the phone, or that guide the user to do so. You can write apps that verify or modify the number the user is calling (for example, to add a long-distance dialing prefix). You can also send and receive SMS (short message service, a.k.a. Text Messages). Of course, both of these capabilities are discussed assuming your device is telephony equipped. Nowadays, a great many Android tablets are WiFi-only, and do not have "3G" or even 2G telephone/SMS capabilities. For these devices, other capabilities such as SMS via Internet and VOIP (Voice Over IP, usually SIP) have to be used.
This chapter covers most of these topics; a few will be found elsewhere in this book.