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On 5 January 1975, the 12-bit field that had been used for dates in the TOPS-10 operating system for DEC PDP-10 computers overflowed, in a bug known as "DATE75". The field value was calculated by taking the number of years since 1964, multiplying by 12, adding the number of months since January, multiplying by 31, and adding the number of days since the start of the month; putting 2 12 − 1 ...
The register width of a processor determines the range of values that can be represented in its registers. Though the vast majority of computers can perform multiple-precision arithmetic on operands in memory, allowing numbers to be arbitrarily long and overflow to be avoided, the register width limits the sizes of numbers that can be operated on (e.g., added or subtracted) using a single ...
Overflow cannot occur when the sign of two addition operands are different (or the sign of two subtraction operands are the same). [1] When binary values are interpreted as unsigned numbers, the overflow flag is meaningless and normally ignored. One of the advantages of two's complement arithmetic is that the addition and subtraction operations ...
Arithmetic and logical instructions set some or all of the flags, and conditional jump instructions take variable action based on the value of certain flags. For example, jz (Jump if Zero), jc (Jump if Carry), and jo (Jump if Overflow) depend on specific flags. Other conditional jumps test combinations of several flags.
Developments were mostly theoretical until the Morris worm, which exploited a buffer overflow in fingerd. [5] The field of computer security developed quickly thereafter, escalating with multitudes of new attacks such as the return-to-libc attack and defense techniques such as the non-executable stack [ 6 ] and address space layout randomization .
The average memory reference time is [1] = + + where = miss ratio = 1 - (hit ratio) = time to make main-memory access when there is a miss (or, with a multi-level cache, average memory reference time for the next-lower cache)
In the C programming language, signed integer overflow causes undefined behavior, while unsigned integer overflow causes the number to be reduced modulo a power of two, meaning that unsigned integers "wrap around" on overflow. This "wrap around" is the cause of the famous "Split Screen" in Pac-Man.
Arbitrary-precision arithmetic can also be used to avoid overflow, which is an inherent limitation of fixed-precision arithmetic. Similar to an automobile's odometer display which may change from 99999 to 00000, a fixed-precision integer may exhibit wraparound if numbers grow too large to represent at the fixed level of precision.