Generally, program modules include {HEAD ~ routines}, programs, objects, components, and data structures, etc. that perform particular tasks or implement {TAIL ~ particular abstract data types} 
Generally , program modules include { HEAD ~ routines } , programs , objects , components , and data structures , etc . that perform particular tasks or implement { TAIL ~ particular abstract data types }
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL