FORTRAN 77 Language Reference

## Real Constants

A real constant is an approximation of a real number. It can be positive, negative, or zero. It has a decimal point or an exponent. If no sign is present, the constant is assumed to be nonnegative.

Real constants, REAL*4, use 4 bytes of storage.

### Basic Real Constant

A basic real constant consists of an optional plus or minus sign, followed by an integer part, followed by a decimal point, followed by a fractional part.

The integer part and the fractional part are each strings of digits, and you can omit either of these parts, but not both.

Example: Basic real constants:

```+82.
-32.
90.
98.5```

### Real Exponent

A real exponent consists of the letter E, followed by an optional plus or minus sign, followed by an integer.

Example: Real exponents:

```E+12
E-3
E6```

### Real Constant

A real constant has one of these forms:

• Basic real constant

• Basic real constant followed by a real exponent

• Integer constant followed by a real exponent

A real exponent denotes a power of ten. The value of a real constant is the product of that power of ten and the constant that precedes the E.

Example: Real constants:

```-32.
-32.18
1.6E-9
7E3
1.6E12
\$1.0E2.0 							Invalid- \$ not allowed, error message
82							Not REAL-need decimal point or exponent
29,002.0 							Invalid -comma not allowed, error message
1.6E39 							Invalid-too large, machine infinity is used
1.6E-39 							Invalid -too small, some precision is lost
```

The restrictions are:

• Other than the optional plus or minus sign, a decimal point, the digits 0 through 9, and the letter E, no other characters are allowed.

• The magnitude of a normalized single-precision floating-point value must be in the approximate range (1.175494E-38, 3.402823E+38).