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A 32-bit register can store 2 32 different values. The range of integer values that can be stored in 32 bits depends on the integer representation used. With the two most common representations, the range is 0 through 4,294,967,295 (2 32 − 1) for representation as an binary number, and −2,147,483,648 (−2 31) through 2,147,483,647 (2 31 − 1) for representation as two's complement.
The rightmost bit represents (−2) 0 = +1, the next bit represents (−2) 1 = −2, the next bit (−2) 2 = +4 and so on, with alternating sign. The numbers that can be represented with four bits are shown in the comparison table below. The range of numbers that can be represented is asymmetric.
A floating-point variable can represent a wider range of numbers than a fixed-point variable of the same bit width at the cost of precision. A signed 32-bit integer variable has a maximum value of 2 31 − 1 = 2,147,483,647, whereas an IEEE 754 32-bit base-2 floating-point variable has a maximum value of (2 − 2 −23) × 2 127 ≈ 3.4028235 ...
It is therefore the maximum value for variables declared as integers (e.g., as int) in many programming languages. The data type time_t, used on operating systems such as Unix, is a signed integer counting the number of seconds since the start of the Unix epoch (midnight UTC of 1 January 1970), and is often implemented as a 32-bit integer. [8]
Programmers may also incorrectly assume that a pointer can be converted to an integer without loss of information, which may work on (some) 32-bit computers, but fail on 64-bit computers with 64-bit pointers and 32-bit integers. This issue is resolved by C99 in stdint.h in the form of intptr_t.
[a] Thus, a signed 32-bit integer can only represent integer values from −(2 31) to 2 31 − 1 inclusive. Consequently, if a signed 32-bit integer is used to store Unix time, the latest time that can be stored is 2 31 − 1 (2,147,483,647) seconds after epoch, which is 03:14:07 on Tuesday, 19 January 2038. [7]
For example, a two's complement signed 16-bit integer can hold the values −32768 to 32767 inclusively, while an unsigned 16 bit integer can hold the values 0 to 65535. For this sign representation method, the leftmost bit (most significant bit) denotes whether the value is negative (0 for positive or zero, 1 for negative).
Also available are the types usize and isize which are unsigned and signed integers that are the same bit width as a reference with the usize type being used for indices into arrays and indexable collection types. [22] Rust also has: bool for the Boolean type. [22] f32 and f64 for 32 and 64-bit floating point numbers. [22] char for a unicode ...