  Interval arithmetic is hardly feasible without directed rounding as provided,
for example, by the IEEE floating-point standard. Equally essential for
interval methods is directed rounding for conversion between the external
decimal and internal binary numerals. This is not provided by the standard I/O
libraries. Conversion algorithms exist that guarantee identity upon conversion
followed by its inverse. Although it may be possible to adapt these algorithms
for use in decimal interval I/O, we argue that outward rounding in radix
conversion is computationally a simpler problem than guaranteeing identity.
Hence it is preferable to develop decimal interval I/O ab initio, which is what
we do in this paper.
