There are two categories of numeric data types: exact and approximate. The exact data types are the integer data types. The approximate data types are the floating point data types.

There are three integer data types: I1 (one-byte), I2 (two-byte), and I4 (four-byte). Integer2 is a synonym for I2 and integer4 is a synonym for I4.

The following table lists the ranges of values for each integer data type:

A floating-point value is represented either as whole plus fractional digits (for example, 123.45) or as a mantissa plus an exponent. The following figure illustrates the mantissa and exponent parts of floating point values.

There are two floating point data types: float4 (4-byte) and float (8-byte). (Real is a synonym for float4, and float8 and double precision are synonyms for float.)

Floating point numbers are double-precision quantities stored in four or eight bytes. The range of float values is processor-dependent, and the precision is approximately 16 significant digits.

For information about the correct notation for a floating-point numeric literal, see Numeric Literals.