Thursday, February 2, 2012

integer overflow c++

integer overflow c++

In binary, we count from 0 to 15 like this: 0, 1, 10, 11, 100, 101, 110, 111, 1000, 1001, 1010, 1011, 1101, 1111. As you can see, the larger numbers require more bits to represent. Because our variables have a fixed number of bits, this puts a limit on the largest number they can hold.

Consider a hypothetical variable that can only hold 4 bits. Any of the binary numbers enumerated above would fit comfortably inside this variable because none of them are larger than 4 bits. But what happens if we try to assign a value that takes 5 bits to our variable? We get overflow: our variable will only store 4 of the 5 bits, and the excess bits are lost.

Overflow occurs when bits are lost because a variable does not have enough memory to store them. We can see this in action with the following program:

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