Open Watcom FORTRAN 77 Language Reference

Names, Data Types and Constants
The type associated with a name defines the type of the data it is to contain. For example, if A is of type
integer, then the storage unit which A occupies is assumed to contain integer data. Note that the data type
of an array element is the same as the data type associated with the array name.
The data type of a function name specifies the type of the result returned by the function when it is
referenced. A name that identifies a specific intrinsic function has type as specified in the chapter entitled
"Functions and Subroutines" on page 243. A generic function name has no type associated with it; its type
is determined by the type of its argument(s). The appearance of a generic function in a type statement is
not sufficient to remove the generic properties of that name. For example, if SIN was declared to be of type
real, it could still be called with an argument of type complex. The type of an external function reference is
determined in the same way as for variables and arrays. The actual type of the external function is
determined implicitly by its name or explicitly by its appearance in a FUNCTION or type statement. Note
that an IMPLICIT statement can affect the type of the external function being defined.
3.4 Constants
A constant can be one of arithmetic, logical or character. Each constant has a data type and value
associated with it and, once established in a program, cannot be changed. Arithmetic constants consist of
those constants whose data type is one of integer, real, double precision, complex or double precision
complex. Logical constants consist of those constants whose data type is logical and character constants
consist of those constants whose data type is character. The string of characters representing a constant
determines its value and data type. The blank character is insignificant for all but character constants.
3.4.1 Integer Constants
An integer constant is formed by a non-empty string of digits preceded by an optional sign.
The following are examples of integer constants.
1423
+345
-34565788
3.4.2 Real Constants
We first define a simple real constant as follows: an optional sign followed by an integer part followed by
a decimal point followed by a fractional part. The integer and fractional parts are non-empty strings of
digits. Either can be omitted but not both.
A real constant has one of the following forms.
1. A simple real constant.
2. A simple real constant followed by an E followed by an optionally signed integer constant.
3. An integer constant followed by an E followed by an optionally signed integer constant.
The optionally signed integer constant that follows the E is called the exponent. The value of a real
constant that contains an exponent is the value of the constant preceding the E multiplied by the power of
ten determined by the exponent.
The following are examples of real constants.
Constants 153