An old operating system created during the late 1970s. CP/M or Control Program for Microcomputers ran on 8 bit microprocessors such as the Intel 8080 or Zilog Z80. Typically these had 4 to 64 kilobytes of RAM and speeds of up to 10 MHz. It was rare for a disk from one CP/M computer to be properly read by a computer from a different company, but was still considered a kind of loose "standard". It faded from popular use by 1985, overtaken by MS-DOS and the Mac OS.