A fuzzy bit , also known as a flaky bit or a weak bit, [1] [2] is a bit cell on a digital storage medium that possesses no clear digital state. [3] This can mean there is some expected statistical distribution for the two possible states, 0 and 1, when the bit cell is read multiple times.
A fuzzy bit may be an unwanted side effect of a defective storage medium or reader, but can also be a deliberately generated effect. For example, in the 1980s and 1990s, with magnetic media such as floppy disks such bits were deliberately created by poor formatting to serve as a copy protection mechanism. An example of this is the game Dungeon Master, in which inconsistency in multiple read access to such a bit was checked when loading the software and was a prerequisite for operation. [4] Since usual floppy disk drives could not produce such bits, this was an effective mechanism for preventing illegal copies and one of the only possible approaches to circumvent such protection was to disable the check routine in the software. [5] [6]
Computer data storage or digital data storage is a technology consisting of computer components and recording media that are used to retain digital data. It is a core function and fundamental component of computers.
The Commodore 1541 is a floppy disk drive which was made by Commodore International for the Commodore 64 (C64), Commodore's most popular home computer. The best-known floppy disk drive for the C64, the 1541 is a single-sided 170-kilobyte drive for 5¼" disks. The 1541 directly followed the Commodore 1540.
The Commodore 1571 is Commodore's high-end 5¼" floppy disk drive, announced in the summer of 1985. With its double-sided drive mechanism, it has the ability to use double-sided, double-density (DS/DD) floppy disks, storing a total of 360 kB per floppy. It also implemented a "burst mode" that improved transfer speeds, helping address the very slow performance of previous Commodore drives.
A floppy disk or floppy diskette is a type of disk storage composed of a thin and flexible disk of a magnetic storage medium in a square or nearly square plastic enclosure lined with a fabric that removes dust particles from the spinning disk. Floppy disks store digital data which can be read and written when the disk is inserted into a floppy disk drive (FDD) connected to or inside a computer or other device.
A disk image is a snapshot of a storage device's structure and data typically stored in one or more computer files on another storage device.
Brain is the industry standard name for a computer virus that was released in its first form on 19 January 1986, and is considered to be the first computer virus for the IBM Personal Computer and compatibles.
ProDOS is the name of two similar operating systems for the Apple II series of personal computers. The original ProDOS, renamed ProDOS 8 in version 1.2, is the last official operating system usable by all 8-bit Apple II series computers, and was distributed from 1983 to 1993. The other, ProDOS 16, was a stop-gap solution for the 16-bit Apple IIGS that was replaced by GS/OS within two years.
Apple DOS is the family of disk operating systems for the Apple II series of microcomputers from late 1978 through early 1983. It was superseded by ProDOS in 1983. Apple DOS has three major releases: DOS 3.1, DOS 3.2, and DOS 3.3; each one of these three releases was followed by a second, minor "bug-fix" release, but only in the case of Apple DOS 3.2 did that minor release receive its own version number, Apple DOS 3.2.1. The best-known and most-used version is Apple DOS 3.3 in the 1980 and 1983 releases. Prior to the release of Apple DOS 3.1, Apple users had to rely on audio cassette tapes for data storage and retrieval.
Data degradation is the gradual corruption of computer data due to an accumulation of non-critical failures in a data storage device. It is also referred to as data decay, data rot or bit rot. This results in a decline in data quality over time, even when the data is not being utilized.
A flash drive is a data storage device that includes flash memory with an integrated USB interface. A typical USB drive is removable, rewritable, and smaller than an optical disc, and usually weighs less than 30 g (1 oz). Since first offered for sale in late 2000, the storage capacities of USB drives range from 8 to 256 gigabytes (GB), 512 GB and 1 terabyte (TB). As of 2023, 2 TB flash drives were the largest currently in production. Some allow up to 100,000 write/erase cycles, depending on the exact type of memory chip used, and are thought to physically last between 10 and 100 years under normal circumstances.
Magnetic storage or magnetic recording is the storage of data on a magnetized medium. Magnetic storage uses different patterns of magnetisation in a magnetizable material to store data and is a form of non-volatile memory. The information is accessed using one or more read/write heads.
Reading is an action performed by computers, to acquire data from a source and place it into their volatile memory for processing. Computers may read information from a variety of sources, such as magnetic storage, the Internet, or audio and video input ports. Reading is one of the core functions of a Turing machine.
Distribution Media Format (DMF) is a format for floppy disks that Microsoft used to distribute software. It allowed the disk to contain 1680 KiB of data on a 31⁄2-inch disk, instead of the standard 1440 KiB. As a side effect, utilities had to specially support the format in order to read and write the disks, which made copying of products distributed on this medium more difficult. An Apple Macintosh computer running Disk Copy 6.3.3 on the Mac OS 7.6 or later operating system can copy and make DMF disks. The first Microsoft software product that uses DMF for distribution were the "c" revisions of Office 4.x. It also was the first software product to use CAB files, then called "Diamond".
A floppy-disk controller (FDC) is a hardware component that directs and controls reading from and writing to a computer's floppy disk drive (FDD). It has evolved from a discrete set of components on one or more circuit boards to a special-purpose integrated circuit or a component thereof. An FDC is responsible for reading data presented from the host computer and converting it to the drive's on-disk format using one of a number of encoding schemes, like FM encoding or MFM encoding, and reading those formats and returning it to its original binary values.
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, Frequency Modulation, or Modified Frequency Modulation.
The Commodore 64 home computer used various external peripherals. Due to the backwards compatibility of the Commodore 128, most peripherals would also work on that system. There is also some compatibility with the VIC-20 and Commodore PET.
Data scrubbing is an error correction technique that uses a background task to periodically inspect main memory or storage for errors, then corrects detected errors using redundant data in the form of different checksums or copies of data. Data scrubbing reduces the likelihood that single correctable errors will accumulate, leading to reduced risks of uncorrectable errors.
A floppy disk is a disk storage medium composed of a thin and flexible magnetic storage medium encased in a rectangular plastic carrier. It is read and written using a floppy disk drive (FDD). Floppy disks were an almost universal data format from the 1970s into the 1990s, used for primary data storage as well as for backup and data transfers between computers.
The floppy disk is a data storage and transfer medium that was ubiquitous from the mid-1970s well into the 2000s. Besides the 3½-inch and 5¼-inch formats used in IBM PC compatible systems, or the 8-inch format that preceded them, many proprietary floppy disk formats were developed, either using a different disk design or special layout and encoding methods for the data held on the disk.
KryoFlux is a hardware and software solution for preserving software on floppy disks. It was developed by the Software Preservation Society.
