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The C language provides the four basic arithmetic type specifiers char, int, float and double (as well as the boolean type bool), and the modifiers signed, unsigned, short, and long.
Two's complement is the most common method of representing signed (positive, negative, and zero) integers on computers, [1] and more generally, fixed point binary values. Two's complement uses the binary digit with the greatest value as the sign to indicate whether the binary number is positive or negative; when the most significant bit is 1 the number is signed as negative and when the most ...
For Integers, the unsigned modifier defines the type to be unsigned. The default integer signedness outside bit-fields is signed, but can be set explicitly with signed modifier. By contrast, the C standard declares signed char, unsigned char, and char, to be three distinct types, but specifies that all three must have the same size and alignment.
This can also be thought of as the most significant bit representing the inverse of its value in an unsigned integer; in an 8-bit unsigned byte, the most significant bit represents the 128ths place, where in two's complement that bit would represent −128. In two's-complement, there is only one zero, represented as 00000000.
Thus, Q12 means a signed integer with any number of bits, that is implicitly multiplied by 2 −12. The letter U can be prefixed to the Q to denote an unsigned binary fixed-point format. For example, UQ1.15 describes values represented as unsigned 16-bit integers with an implicit scaling factor of 2 −15 , which range from 0.0 to (2 16 −1)/2 ...
an 11-bit binary exponent, using "excess-1023" format. Excess-1023 means the exponent appears as an unsigned binary integer from 0 to 2047; subtracting 1023 gives the actual signed value; a 52-bit significand, also an unsigned binary number, defining a fractional value with a leading implied "1" a sign bit, giving the sign of the number.
In a move or convert operation, zero extension refers to setting the high bits of the destination to zero, rather than setting them to a copy of the most significant bit of the source. If the source of the operation is an unsigned number, then zero extension is usually the correct way to move it to a larger field while preserving its numeric ...
All C integer types have signed and unsigned variants. If signed or unsigned is not specified explicitly, in most circumstances, signed is assumed. However, for historic reasons, plain char is a type distinct from both signed char and unsigned char. It may be a signed type or an unsigned type, depending on the compiler and the character set (C ...