 In most cases the designs were fairly crude, with the entire address and data buses exposed by the port and attached via an edge connector; the cartridge was memory mapped directly into the system's address space such that the CPU could execute the program in place without having to first copy it into expensive RAM.The Texas Instruments TI 59 family of programmable scientific calculators used interchangeable ROM cartridges that could be installed in a slot at the back of the calculator.The calculator came with a module that provides several standard mathematical functions including solution of simultaneous equations.