What does the increment operation ++ do in a programming language?

Increases the value of a variable by one.

There are prefix and postfix forms:

• Prefix (++x): First increases the value of the variable, then returns the new value.
• Postfix (x++): First returns the current value of the variable, then increases its value.

Example:

var a = 5
var b = ++a // a becomes 6, b becomes 6

var c = 5
var d = c++ // c becomes 6, d becomes 5

In Swift 3 and above, the ++ operator has been removed. Instead, the addition assignment operator += 1 is used.

var e = 5
e += 1 // e becomes 6