The ATerm format is a generic internal and external representation of data by means of simple prefix terms. ATerms have the form

t := C(t1,...,tn) | C | n | "ccc" | r | [t1,....,tn]

where n stands for the decimal numbers, "ccc" for a string, r for a real.

The ATermLibrary implements the internal representation of ATerms and the conversion between the external and the internal representation. ATerms can also be represented in an efficient binary format in which complete sharing of subterms is maintained.