INFORMATION TERMINAL DEVICE AND METHOD FOR PURCHASING AND ADDING ADDITIONAL PROGRAM FUNCTIONS

An information terminal device and method for upgrading a program simply and flexibly and an upgraded program is described. In many cases, a program running on a computer has additional functions prepared separately so that they can be added to that program as necessary. To use the additional functions, a user may purchase a new version of that program and install it on their computer by selecting icons which link to the new version of the program.