Codes have been used in Calculating, EBCDIC, Fielded etc., with various bit mixes, and total bits between 8 and 5. This frequently depended upon which proprietary computer system you are using, and which sort of device you were using. Punched cards had another code. A typical code, ASCII, was finally introduced. The American Standard Code for Information Interchange has 8 bits, and is used interchangeably on about all systems today. Paper tape was updated to 8 Bits across, in addition to the sprocket, and used to boot computers, and also to transfer data from one machine to another. For example a NC, or Numerical Control, could use paper tape to relay instructions to a machine for cutting steel sheet contours.
Punch cards had been used since the 19th century, and two or three different formats had emerged, round holes, rectangular holes, 80 per cent, 90 per cent, separate codes, etc Once more it depended upon whose computer you are using IBM, Univac, Control Data etc However, the principle was the same. The ‘standard’ came to be the 80-column card, with 12 rows for every character. The 1 to 9 rows were numbers 1-9, with the 0, 11 and 12 rows used for do my coding various special characters, shifts etc Magnetic tape, originally on 10 Inch reels of half inch wide tape, 2400 feet long, used variants of the codes. Originally 6 bits and parity 7 were written throughout the tape. With the coming of bytes that increased to 9 pieces to integrate the 8-bit byte and parity.
Most versions here have been from the recording system, which is the way the information is written to and read from the tape. These include NRZ Non Return to Zero, PE Phase Enabled and, latterly GCR Group Controlled Recording. The density potential has increased, so the capacity of the tapes in the present day little cassettes has significantly improved. Transport Procedures, initially ‘Stop-Start’, to record each personality, now more commonly ‘Streaming’, have grown in parallel. The cassette has generally been written in blocks of different lengths with codes being required to control them, such as ‘Start of Block’, ‘Start of Data’ etc. Other codes are utilized to confirm the data. The DAT Digital Audio Tape tapes used today use another kind of electronic coding, but information codes are much the same.