Floating-Point Data Types

Floating-Point Data Types

Type                                                Range                                                                Precision                                Bytes

Float (Single)                                ± 1.5e-45..3.4e+38                                7-8                                4

Real                                                ± 2.9e-39..1.7e+38                                11-12                                6

Double (Double)                                ± 5.0e-324..1.7e+308                                15-16                                8

Long Double (Extended)                ± 3.4e-4932..1.1e+4932                                19-20                                10

The type names originate from the C programming language. The corresponding Pascal names are specified in brackets. The Real type exists only in Pascal. The Data Interpreter is capable of translating hex values in an editor window into floating-point numbers of all four types and vice-versa.

In the computer, a floating-point number F is represented by a mantissa M and an exponent E, where M × 2^E = F. Both M and E are signed integer values themselves. The four data types differ in their value ranges (i.e. the number of bits reserved for the exponent) and in their precision (i.e. the number of bits reserved for the mantissa).

On Intel-based systems, calculations upon floating-point numbers are carried out by a math coprocessor while the main processor waits. The Intel 80x87 uses 80-bit precision for calculations, whereas RISC processors often use 64-bit precision.