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Meaning of CDR

 
Computing Dictionary
 
 Definition: 

/ku'dr/ or /kuh'dr/ [LISP] To skip past the first item from a list of things (generalised from the LISP operation on binary tree structures, which returns a list consisting of all but the first element of its argument). In the form "cdr down", to trace down a list of elements: "Shall we cdr down the agenda?" Usage: silly. See also loop through.

Historical note: The instruction format of the IBM 7090 that hosted the original LISP implementation featured two 15 bit fields called the "address" and "decrement" parts. The term "cdr" was originally "Contents of Decrement part of Register". Similarly, "car" stood for "Contents of Address part of Register".

The cdr and car operations have since become bases for formation of compound metaphors in non-LISP contexts. gls recalls, for example, a programming project in which strings were represented as linked lists; the get-character and skip-character operations were of course called CHAR and CHDR.

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