What does ":=" do?

Question

http://en.wikipedia.org/wiki/Equals_sign#In_computer_programming

In computer programming languages, the equals sign typically denotes either a boolean operator to test equality of values (e.g. as in Pascal or Eiffel), which is consistent with the symbol's usage in mathematics, or an assignment operator (e.g. as in C-like languages). Languages making the former choice often use a colon-equals (:=) or ≔ to denote their assignment operator. Languages making the latter choice often use a double equals sign (==) to denote their boolean equality operator.

Note: I found this by searching for colon equals operator

It's the assignment operator in Pascal and is often used in proofs and pseudo-code. It's the same thing as = in C-dialect languages.

Historically, computer science papers used = for equality comparisons and ← for assignments. Pascal used := to stand in for the hard-to-type left arrow. C went a different direction and instead decided on the = and == operators.

In the statically typed language Go := is initialization and assignment in one step. It is done to allow for interpreted-like creation of variables in a compiled language.

// Creates and assigns
answer := 42

// Creates and assigns
var answer = 42

Another interpretation from outside the world of programming languages comes from Wolfram Mathworld, et al:

If A and B are equal by definition (i.e., A is defined as B), then this is written symbolically as A=B, A:=B, or sometimes A≜B.

■ http://mathworld.wolfram.com/Defined.html

■ https://math.stackexchange.com/questions/182101/appropriate-notation-equiv-versus

Some language uses := to act as the assignment operator.

In a lot of CS books, it's used as the assignment operator, to differentiate from the equality operator =. In a lot of high level languages, though, assignment is = and equality is ==.

A number of programming languages, most notably Pascal and Ada, use a colon immediately followed by an equals sign (:=) as the assignment operator, to distinguish it from a single equals which is an equality test (C instead used a single equals as assignment, and a double equals as the equality test).

Reference: Colon (punctuation).