These days, most computers use the same internal data formats for integer and floating-point data, if one ignores little differences like big- versus little-endian byte ordering. However, occasionally it is necessary to exchange data between systems with incompatible data formats. This is what portable files are designed to do.
The portable file format is mostly obsolete. System files (see System File Format) are a better alternative.
Please note: This information is gleaned from examination of ASCII-formatted portable files only, so some of it may be incorrect for portable files formatted in EBCDIC or other character sets.