Objective-C Float, Double, Decimal

April 12, 2009 § 3 Comments

Float – 7 digits (32 bit)

Double-15-16 digits (64 bit)

Decimal -28-29 significant digits (128 bit)

Decimals have much higher precession and usually used within financial applications that require a high degree of accuracy. Decimals are much slower (up to 20X times in some tests) than a double\float.

Decimals and Floats/Doubles cannot be compared without a cast whereas Floats and Doubles can. Decimals also allow the encoding or trailing zeros.

Decimal doesn’t use IEEE floating point representation. It uses a decimal representation that is 100% accurate by doing decimal based math rather than base 2 based math. You can trust math to within the accuracy of decimal precision whereas you can’t fully trust floats or doubles unless you are very careful.

float is a single precision (32 bit) floating point data type as defined by IEEE 754 (it is used mostly in graphic libraries).

double is a double precision (64 bit) floating point data type as defined by IEEE 754 (probably the most normally used data type for real values).

decimal is a 128-bit floating point data type, it should be used where precision is of extreme importance (monetary calculations).

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