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)