How deeply does Modern C cover hexadecimal floating-point constant?

Explains syntax, approximation, representation, and suffix-selected types, but does not develop floating-point internals.

Hexadecimal floating-point constant

As explained in Modern C

A hexadecimal floating-point constant is a C floating-point literal written with hexadecimal significand digits and a binary power exponent.

Consider 0x1.99999AP-3: its hexadecimal significand is combined with a binary power exponent, making the literal correspond closely to a floating-point binary representation. section 5.3

A precise spelling for an approximate value

The decimal constant 0.2 may be stored as approximately 0.2000000000000000111. The hexadecimal constant 0x1.99999AP-3 represents approximately 0.20000000298, while 0xC.CCCCCCCCCCCCCCDP-6 represents approximately 0.200000000000000000003. Their spellings look distant, but their values are close. On most modern architectures, hexadecimal floating-point constants with few digits exactly match their literal values. section 5.3

TAKEAWAY: A floating-point literal has value, type, and binary representation.

Use a trailing f or F for float, l or L for long double; without a suffix, the constant has type double. section 5.3

How Modern C covers it

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Modern C, Third EditionA hexadecimal floating-point literal is a C floating-point literal written with a hexadecimal significand and a binary exponent introduced by P or p.

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Related concepts

C99produced by · C99 is the ISO standard revision of the C programming language published in 1999.
literalkind of · A literal is a language construct that directly denotes a fixed value or specifies an exact value permitted by a type.
binary representationequivalent to · Binary representation expresses information or values using a base-two positional system with two symbols, conventionally zero and one.
hexadecimal numbercontrasts with · A hexadecimal number is a numeral represented in the base-sixteen positional system using symbols 0–9 and A–F for values zero through fifteen.
floating-point constantkind of · A floating-point constant is source-code numeric literal syntax that denotes a value in a floating-point type.

This explainer was generated by Manning's knowledge graph from the text of Modern C. The section links point to the parts of the book it draws on.