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An integer overflow can cause the value to wrap and become negative, which violates the program's assumption and may lead to unexpected behavior (for example, 8-bit integer addition of 127 + 1 results in −128, a two's complement of 128).
[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, if the type of a variable as specified in the source code is narrower than the native register width (such as int on a 64-bit machine, a common scenario), then the compiler can safely use a signed 64-bit integer for the variable in the machine code it produces, without changing the defined behavior of the code. If a program ...
An example, suppose we add 127 and 127 using 8-bit registers. 127+127 is 254, but using 8-bit arithmetic the result would be 1111 1110 binary, which is the two's complement encoding of −2, a negative number. A negative sum of positive operands (or vice versa) is an overflow.
In the C# programming language, or any language that uses .NET, the DateTime structure stores absolute timestamps as the number of tenth-microseconds (10 −7 s, known as "ticks" [80]) since midnight UTC on 1 January 1 AD in the proleptic Gregorian calendar, [81] which will overflow a signed 64-bit integer on 14 September 29,228 at 02:48:05 ...
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).
Additionally, POSIX includes ssize_t, which is a signed integer type of the same width as size_t. ptrdiff_t is a signed integer type used to represent the difference between pointers. It is guaranteed to be valid only against pointers of the same type; subtraction of pointers consisting of different types is implementation-defined.
For example, in an eight-bit byte, only seven bits represent the magnitude, which can range from 0000000 (0) to 1111111 (127). Thus numbers ranging from −127 10 to +127 10 can be represented once the sign bit (the eighth bit) is added. For example, −43 10 encoded in an eight-bit byte is 10101011 while 43 10 is 00101011.