1) For a given font , cpi (characters per inch) is the number of typographic character that will fit on each inch of a printed line. The measurement applies mainly to monospace ( fixed-width ) fonts. Fonts with characters of proportional (varying) widths have an average cpi.
2) cpi (cyles per instruction, or clocks per instruction) is the number of computer clock speed cycles (alternating current pulses) that occur while a computer instruction is being executed (performed by the computer processor). The number of cycles per instruction can be reduced by using pipelining . In some superscalar processors, more than one instruction can be performed during a single clock cycle.
3) CPI (Common Programming Interface) is the application program interface ( API ) specified as part of IBM's proprietary software architecture, the Systems Application Architecture ( SNA ).