It was while troubleshooting a fault in an early Intel product that Frohman in 1970 developed the concept for the EPROM, the first non-volatile semiconductor memory that was both erasable and easily reprogrammable. At the time, there were two types of semiconductor memories. Random-access memory (RAM) chips were easy to program, but a chip would lose its charge (and the information encoded on the chip) when its power source was turned off. In industry parlance, RAM chips were "volatile". Read-only memory (ROM) chips, by contrast, were "nonvolatile"—that is, the information encoded in the chip was fixed and unchangeable. But the process for programming ROM memories was time-consuming and cumbersome. Typically, the data had to be “burned in” at the factory: physically embedded on the chip through a process called “masking” that generally took weeks to complete. And once programmed, the data in the ROM chip could not be altered.