. ▁An ▁interpreter ▁can ▁be ▁viewed ▁as ▁being ▁part ▁transl ator , ▁and ▁part ▁execution ▁model ▁implementation . ▁ ▁Each ▁and ▁every ▁programming ▁language ▁has ▁an ▁execution ▁model , ▁which ▁determ ines ▁the ▁manner ▁in ▁which ▁the ▁units ▁of ▁work ▁( that ▁are ▁indicated ▁by ▁program ▁syntax ) ▁are ▁scheduled ▁for ▁execution . ▁D etailed ▁examples ▁of ▁the ▁specification ▁of ▁execution ▁models ▁of ▁a ▁few ▁popular ▁languages ▁include ▁those ▁of ▁Python , ▁ ▁the ▁execution ▁model ▁of ▁the ▁Un ified ▁Par allel ▁C ▁( UP C ) ▁programming ▁language , ▁ ▁a ▁discussion ▁of ▁various ▁classes ▁of ▁execution ▁model ▁such ▁as ▁for ▁imper ative ▁versus ▁functional ▁languages , ▁ ▁and ▁an ▁article ▁discuss ing ▁execution ▁models ▁for ▁real - time ▁embedded ▁languages . ▁ ▁Over view ▁ ▁As ▁a ▁simple ▁example ▁of ▁a ▁basic ▁execution ▁model , ▁that ▁of ▁the ▁C ▁language ▁is ▁described ▁in ▁the ▁book ▁by ▁K ern igh an ▁and ▁Rich ie . ▁The ▁book ▁describes ▁that ▁work ▁takes ▁places ▁in ▁units ▁called ▁statements , ▁which ▁are ▁s ynt act ically ▁indicated ▁by ▁a ▁termin ating ▁"; ". ▁It ▁spec ifies ▁that ▁statements ▁are ▁completed ▁serial ly ▁( one ▁at ▁a ▁time ) ▁and ▁sequ entially ▁( a ▁previous ▁statement ▁comple tes ▁before ▁the ▁next ▁statement ▁begins ). ▁Details ▁such ▁as ▁this ▁are ▁part ▁of ▁the ▁execution ▁model . ▁ ▁In ▁the ▁modern ▁age , ▁parallel ▁programming ▁is ▁an ▁increasing ly ▁important ▁topic . ▁Par allel ▁execution ▁models ▁( se ver al ▁at ▁a ▁time ) ▁are ▁much ▁more ▁complex