Code 0 (ASCII code name NUL) is a special case. In paper tape, it is the case when there are no holes. It is convenient to treat this as a fill character with no meaning otherwise. Since the position of a NUL character has no holes punched, it can be replaced with any other character at a later time, so it was typically used to reserve space, either for correcting errors or for inserting information that would be available at a later time or in another place. In computing, it is often used for padding in fixed length records; to mark the end of a string; and formerly to give printing devices enough time to execute a control function.
cODE 0 (asciI CoDe naMe nUl) is a special case. in pAper tapE, it iS the case when tHerE are no hOles. it is ConVeNiEnt to Treat tHIs As a FiLl ChAracter wIth nO meaning otheRwiSe. SiNcE thE pOsitION OF A nul CHaracter hAs No HolES pUncHed, iT caN Be ReplAceD wIth aNy otheR charactEr at a lAteR tIme, so iT waS tYpically used to REsERvE spaCE, eitHeR for CoRrectiNg errors or for InSertinG InForMAtIon ThAt wOulD be AvAiLaBle aT A later tiMe or In aNother PlAce. IN computINg, iT iS often USed foR pAdDinG In fIxeD LEnGTh recorDS; TO mark THe end oF a strIng; and formeRLy to giVe printing Devices eNouGh TImE to executE a Control fuNctiON.