A bignum system in a computer or program allows internal representation of arbitrarily large integers or arbitrarily precise rational numbers. Numbers are typically stored as (ratios of) digit lists which can grow using dynamically allocated memory.

First implemented in MacLISP, bignum facilities are available in most modern Lispss and in many other languages (Java, Perl, Ruby, Python, Squeak). The VAX/VMS operating system offered bignum facilities as a collection of string functionss. The GNU Multi-Precision Library is a free C library that offers bignum features. All computer algebra systems contain bignum facilities.

Bignum systems often employ fast multiplication algorithms.

See also: large numbers.