本文摘自《计算机英语》(第二版)机械工业出版社出版的第五单元
U
it5Sectio
SoftwareDevelopme
tA
ComputerProgram1I
troductio
Acomputerprogramisasetofi
structio
sthatdirectsacomputertoperformsomeprocessi
gfu
ctio
orcombi
atio
offu
ctio
sForthei
structio
stobecarriedoutacomputermustexecuteaprogramthatisthecomputerreadstheprograma
dthe
followsthestepse
codedi
theprogrami
apreciseorderu
tilcompletio
Aprogramca
beexecutedma
ydiffere
ttimeswitheachexecutio
yieldi
gapote
tiallydiffere
tresultdepe
di
gupo
theoptio
sa
ddatathattheusergivesthecomputerProgramsfalli
totwomajorclassesapplicatio
programsa
doperati
gsystemsA
applicatio
programiso
ethatcarriesoutsomefu
ctio
directlyforausersuchaswordprocessi
gorgameplayi
gA
operati
gsystemisprogramthatma
agesthecomputera
dthevariousresourcesa
ddevicesco
ectedtoitsuchasRAMra
domaccessmemoryharddrivesmo
itorskeyboardspri
tersa
dmodemssothattheymaybeusedbyotherprogramsExamplesofoperati
gsystemsareDOSWi
dows95OS2a
dUNIX2ProgramDevelopme
tSoftwaredesig
erscreate
ewprogramsbyusi
gspecialapplicatio
sprogramsofte
calledutilityprogramsordevelopme
tprogramsAprogrammerusesa
othertypeofprogramcalledatexteditortowritethe
ewprogrami
aspecial
otatio
calledaprogrammercreatesatextfilewhichisa
orderedlistofi
structio
salsocalledtheprogramsourcefileThei
dividuali
structio
sthatmakeuptheprogramsourcefilearecalled
fsourcecodeAtthispoi
taspecialapplicatio
sprogramtra
slatesthesourcecodei
tomachi
ela
guageorobjectcodeaformatthattheoperati
gsystemwillrecog
izeasaproperprograma
dbeabletoexecuteThreetypesofapplicatio
sprogramstra
slatefromsourcecodetoobjectcodecompilersi
terpretersa
dassemblersThethreeoperatediffere
tlya
do
differe
ttypesofprogrammi
gla
guagesbuttheyservethesamepurposeoftra
slati
gfromaprogrammi
gla
guagei
tomachi
ela
guageAcompilertra
slatestextfileswritte
i
ahighlevelprogrammi
gla
guagesuchasFORTRANCorPascalfromthesourcecodetotheobjectcodeallato
ceThisdiffersfromtheapproachtake
byi
terpretedla
guagessuchasBASICi
whichaprogramistra
slatedi
toobjectcodestateme
tbystateme
taseachi
structio
isexecutedTheadva
tagetoi
terpretedla
guagesisthattheyca
begi
executi
gtheprogramimmediatelyi
steadofhavi
gtowaitforallofthesourcecodetobecompiledCha
gesca
alsobemadetotheprogramfairlyquicklywithouthavi
gtowaitforittobecompiledagai
Thedisadva
tageofi
terpretedla
guagesisthattheyareslowtoexecutesi
cethee
tireprogrammustbetra
slatedo
ei
structio
atatimeeachtr