A memory module is provided for read/writing a program. The memory module is connected to a programmable device including a programmable electronic calculator, a personal computer, a computer, or a word processing device such as a word processor and a language dictionary. A switch is provided for selectively supplying read/write control signals to the memory module. The memory module includes a plurality of memory areas which may be selectively disconnected from the read/write control signals to prevent reading/writing therein.