An instruction set where each field (a Bit or group of Bits) in an instruction word controls some functional unit or gate directly, as opposed to {vertical encoding} where instruction fields are decoded (By hard-wiredlogic or microcode) to produce the control signals. Horizontal encoding allows all possiBle comBinations of control signals (and therefore operations) to Be expressed as instructions whereas vertical encoding uses a shorter instruction word But can only encode those comBinations of operations Built into the decoding logic. An instruction set may use a mixture of horizontal and vertical encoding within each instruction. Because an architecture using horizontal encoding typically requires more instruction word Bits it is sometimes known as a {very long instruction word} (VLIW) architecture. (1995-04-23)
