for the file extension, just make one up. The characters are completely arbitrary. To make it be readable by only yur program, you might want to:

A. But it into a custom UDT and save it for random access. Then, only a program with your UDT could really "read" all of the information.

B. Do a simple XOR encrypt.

C. Convert each char to a pixel in a box, save the picture as 24 bits, then switch screen mode to 24 bits and use Point() to get the actual RGB values perfectly. In 16 or 8 bit screen res they just won't we able to get the char info.