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(Corresponds to Section 4.2 of ANSI X3.9-1978 FORTRAN 77.)
A typeless constant has one of the following forms:
'binary-digits'B 'octal-digits'O 'hexadecimal-digits'Z 'hexadecimal-digits'X
binary-digits, octal-digits, and hexadecimal-digits are nonempty strings of characters in the set `01', `01234567', and `0123456789ABCDEFabcdef', respectively. (The value for `A' (and `a') is 10, for `B' and `b' is 11, and so on.)
A prefix-radix constant, such as `Z'ABCD'', can optionally be treated as typeless. See section Options Controlling Fortran Dialect, for information on the `-ftypeless-boz' option.
Typeless constants have values that depend on the context in which they are used.
All other constants, called typed constants, are interpreted--converted to internal form--according to their inherent type. Thus, context is never a determining factor for the type, and hence the interpretation, of a typed constant. (All constants in the ANSI FORTRAN 77 language are typed constants.)
For example, `1' is always type
INTEGER(KIND=1) in GNU
Fortran (called default INTEGER in Fortran 90),
`9.435784839284958' is always type
REAL(KIND=1) (even if the
additional precision specified is lost, and even when used in a
REAL(KIND=2) context), `1E0' is always type
and `1D0' is always type
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