Numbers are always converted using the decimal number base: there is no provision in Standard Fortran for transfers in other number bases such as octal or hexadecimal. More complicated conversions such as these can be performed with the aid of internal files.
On output number are generally right-justified in the specified field; leading blanks are supplied where necessary. Negative values are always preceded by a minus sign (for which space must be allowed in the field); zero is always unsigned; the SP and SS descriptors control whether positive numbers are to be preceded by a plus sign or not. A number which is too large to fit into its field will appear instead as a set of w asterisks.
On input numbers should be right-justified in each field. All forms of constant permitted in a Fortran program can safely be used in an input field of the corresponding type, as long there are no embedded or trailing blanks. Leading blanks are always ignored; a field which is entirely blank will be read as zero. The treatment of embedded and trailing blanks can be controlled with the BN and BZ descriptors. The rules here are another relic of very early Fortran systems.
When reading a file which has been connected by means of an OPEN statement (provided it does not contain BLANK='ZERO') all embedded and trailing blanks in numeric input fields are treated as nulls, i.e. they are ignored. In all other cases, such as input from the standard pre-connected file or from an internal file, embedded and trailing blanks are treated as zeros. These defaults can be altered with the BN and BZ control descriptors. It is hard to imagine any circumstances in which it is desirable to interpret embedded blanks as zeros; the default settings are particularly ill-chosen since numbers entered by a user at a terminal are often left-justified and may appear to be padded out with zeros. Errors from this source can be avoided by using BN at the beginning of all input format specifications.