This manual provides readers with a step-by-step examination of the development of encryption techniques from the Caesar cipher to modern-day public and private key encryption methods. It gives examples which show how messages, files and notes can be programmed with different levels of security. Numerous techniques are explained in detail, followed by the development of program modules in both Basic and C++. The companion CD-ROM contains all the Basic and C++ source code for the enciphering and deciphering programs described in the book, along with executable versions of these programs.