I found out how to use double numbers in the Psion L1VM. The bytecode of the L1VM (.l1obj) uses the modern IEEE 64 bit double numbers. The ARM CPU in the Psion 5MX uses a different format for double numbers. So how can this be fixed? In my "math circle" program I defined Pi as a string. Then the string is converted to a double number. This just works fine. You need to do this with any double number you want to use.