Constants

  A constant has a value which is fixed when the program is written. The data type of every constant is evident from its form. Arithmetic constants always use the decimal number base: Standard Fortran does not support other number bases such as octal or hexadecimal.

Although arithmetic constants may in general have a leading sign (plus or minus) there are some circumstances in Fortran when an unsigned constant is required. If the constant is zero then any sign is ignored.