ANiNstructioN 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. ANiNstructioN 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)
