Delphi in a Nutshell

Name

Single Type

Syntax

type Single;

Description

The Single type is an IEEE standard floating-point type that uses 4 bytes to store a sign bit, an 8-bit exponent, and a 23-bit mantissa. The mantissa is usually normalized, that is, it has an implicit 1 bit before the most significant bit. If the exponent is zero, however, the mantissa is denormalized—without the implicit 1 bit. Thus, the numerical value of 0.0 is represented by all zero bits. An exponent of all 1 bits represents infinity (mantissa is zero) or not-a-number (mantissa is not zero).

The limits of Single are roughly 1.18 × 10^-38 to 3.40 × 1038, with about seven decimal digits of precision. Table 5-3 shows the detailed format of finite and special Single values.

Table 5-3. Format of Single Floating-Point Numbers

Numeric class	Sign	Exponent	Mantissa
Positive
Normalized	0	0...1 to 1...10	0...0 to 1...1
Denormalized	0	0...0	0...1 to 1...1
Zero	0	0...0	0...0
Infinity	0	1...1	0...0
Signaling NaN	0	1...1	0...1 to 01...1
Quiet NaN	0	1...1	1...0 to 1...1
Negative
Normalized	1	0...1 to 1...10	0...0 to 1...1
Denormalized	1	0...0	0...1 to 1...1
Zero	1	0...0	0...0
Infinity	1	1...1	0...0
Signaling NaN	1	1...1	0...1 to 01...1
Quiet NaN	1	1...1	1...0 to 1...1

Tips and Tricks

• The Single type corresponds to the float type in Java, C, and C++.

• Single is usually used when memory is at a premium. It does not usually offer a performance advantage over Double, and it suffers from a limited ...