Table of contentsClick link to navigate to the desired location
This content has been automatically translated from Ukrainian.
You have a counter that can only count to a certain number. For example, a pocket calculator that shows the maximum 999. If you try to add 1 to 999, it won't be able to show 1000 - the numbers will simply "overflow" and the calculator will show something completely different, for example 000.
In programming, such an effect is called integer overflow (integer overflow).
This happens when the number becomes larger than the maximum value that the selected variable type can store.
For example, if the variable int can store numbers up to 2,147,483,647, then adding 1 will make its value... negative!
Why 2,147,483,647 is the "ceiling" for a 32-bit number
In a computer, numbers are stored in binary form (that is, as a sequence of zeros and ones).
"32-bit" means that a number is allocated to store 32 cells, and each can have either 0 or 1.
But if the number signed (with sign), then one of these cells is reserved for sign:
- 0 in the first bit — the number is positive,
- 1 in the first bit — the number is negative.
That is, instead of 32 bits, only the number remains for the value 31 bits.
Maximum value When all 31 bits (except the sign) are filled with units, we get the largest possible positive number:
1111111111111111111111111111111
In the decimal system, this is just the case 2,147,483,647. In hexadecimal (hex) form, this is written as 0x7FFFFFFF:
- 7 — is binary 0111 (ie sign 0 + three units),
- F — is binary 1111 (four units),
- and so on until the end.
Because of this, very strange bugs sometimes occur in programs, and there have even been serious accidents due to overflow in history. even memes occur due to an integer overflow error, but this is not accurate.
This post doesn't have any additions from the author yet.
