Bit nibbler

A bit nibbler, or nibbler, is a computer software program designed to copy data from a floppy disk one bit at a time. It functions at a very low level directly interacting with the disk drive hardware to override a copy protection scheme that the floppy disk's data may be stored in. In most cases the nibbler software still analyses the data on a byte level, only looking to the bit level when dealing with synchronization marks (syncs), zero-gaps and other sector & track headers. When possible, nibblers will work with the low-level data encoding format used by the disk system, being Group Coded Recording (GCR - Apple, Commodore), Frequency Modulation (FM - Atari), or Modified Frequency Modulation (MFM - Amiga, Atari, IBM PC).

Software piracy began to be a problem when floppy disks became the common storage media. The ease of copying depended on the system; Jerry Pournelle wrote in BYTE in 1983 that "CP/M doesn't lend itself to copy protection" so its users "haven't been too worried" about it, while "Apple users, though, have always had the problem. So have those who used TRS-DOS, and I understand that MS-DOS has copy protection features". Apple and Commodore 64 copy protection schemes were extremely varied and creative because most of the floppy disk reading and writing was controlled by software (or firmware), not by hardware.

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