In data processing

Data processing

Computer data processing is any process that a computer program does to enter data and summarise, analyse or otherwise convert data into usable information. The process may be automated and run on a computer. It involves recording, analysing, sorting, summarising, calculating, disseminating and...

, a scratch tape is a magnetic tape

Magnetic tape data storage

Magnetic tape data storage uses digital recording on to magnetic tape to store digital information. Modern magnetic tape is most commonly packaged in cartridges and cassettes. The device that performs actual writing or reading of data is a tape drive...

 that is used for temporary storage and can be reused or erased after the completion of a job or processing run. During the early years of computing, when magnetic tape was the primary form of mass storage, many programs, notably sorting routines

Merge sort

Merge sort is an O comparison-based sorting algorithm. Most implementations produce a stable sort, meaning that the implementation preserves the input order of equal elements in the sorted output. It is a divide and conquer algorithm...

, required such temporary storage. The term can also be used to refer to a tape that had been used to store data that has now expired, if that tape is expected to be reused to store similar data, such as during a backup rotation.

See also

• Scratch space
  Scratch space
  Scratch space is space on the hard disk drive that is dedicated for only temporary storage. It cannot be used to permanently backup files. Scratch disks can be set to erase all data at regular intervals so that the disk space is left free for future use...
  
   – contemporary equivalent
• Merge sorting tape drives – paradigm application
• Scratch monkey
  Scratch monkey
  A Scratch Monkey is a term used in hacker jargon, as in "Before testing or reconfiguring, always mount a scratch monkey", a proverb used to advise caution when dealing with irreplaceable data or devices...
  
  – use in computer proverb