Older operating systems such as TOPS-10, along with CP/M, tracked file length only in units of disk blocks and used Control-Z (SUB) to mark the end of the actual text in the file. For this reason, EOF, or end-of-file, was used colloquially and conventionally as a three-letter acronym for Control-Z instead of SUBstitute. The end-of-text code (ETX), also known as Control-C, was inappropriate for a variety of reasons, while using Z as the control code to end a file is analogous to it ending the alphabet and serves as a very convenient mnemonic aid. A historically common and still prevalent convention uses the ETX code convention to interrupt and halt a program via an input data stream, usually from a keyboard.

Answer this question, if possible (if impossible, reply "unanswerable"): What did older operating systems use to mark the end of the text?
Control-Z (SUB)
Äldre operativsystem som TOPS-10, tillsammans med CP/M, spårade fillängden endast i enheter av diskblock och använde Control-Z (SUB) för att markera slutet på den faktiska texten i filen. Av denna anledning användes EOF, eller end-of-file, kollokvialt och konventionellt som en trebokstavsakronym för Control-Z istället för Substituerad. End-of-text code (ETX), även känd som Control-C, var olämpligt av en mängd olika skäl, medan Z som kontrollkod för att avsluta en fil är analog med den som avslutar alfabetet och fungerar som en mycket bekväm mnemonisk hjälp. En historiskt vanlig och fortfarande förhärskande konvention använder ETX-kodkonventionen för att avbryta och stoppa ett program via en inmatningsdataström, oftast från ett tangentbord. Svara på denna fråga, om möjligt (om möjligt svara "osvarbart"): Vad använde äldre operativsystem för att markera slutet på texten?
Older operating systems such as TOPS-10, along with CP/M, tracked the file length only in disk block drives and used Control-Z (PDO) to mark the end of the actual text in the file. For this reason, EOF, or end-of-file, was colloquially and conventionally used as a three-letter acronym for Control-Z instead of Substitute. End-of-text code (ETX), also known as Control-C, was inappropriate for a variety of reasons, while Z as control code to terminate a file is analogous to the one ending the alphabet and serves as a very convenient mnemonic help. A historically common and still prevalent convention uses the ETX Code Convention to cancel and stop a program via an input data stream, usually from a keyboard. Answer this question, if possible (if possible answer "unanswerable"): What used older operating systems to mark the end of the text?
Control-Z (SUB)
Control-Z (PDO)