integer overflow

integers have a limited amount of space

The 4 usual sizes for integers are 8 bits, 16 bits, 32 bits, and 64 bits

the biggest 8-bit unsigned integer is 255

… so what happens if you do 255 + 1? going above/below the limits is called overflow

the result wraps around to the other side

255 + 1 = 0
255 + 3 = 2
200 * 2 = 144
0 - 2 = 254

maximum numbers for different sizes

bits: unsigned signed

8: 127 255

16: 32767 65535

32: 2 billion ~4 billion

64: ~9 quintillion ~18 quintillion

overflows often don’t throw errors

computer (thinking): “255 + 1? that number is 8 bits, so the answer is 0! that’s what you wanted right?”

This can cause VERY tricky bugs

some languages where integer overflow happens

Java/Kotlin
C/C++
Rust
Swift
C#
SQL
R
Go
Dart
Python (only in numpy)

Some throw errors on overflow, some don’t, for some it depends on various factors. Look up how it works in your language!