The following function capitalizes each word in a string. It has one parameter, named input, and five local variables, which are written as extra parameters.

# capitalize each word in a string
function capitalize(input,    result, words, n, i, w)
{
	result = ""
	n = split(input, words, " ")
	for (i = 1; i <= n; i++) {
		w = words[i]
		w = toupper(substr(w, 1, 1)) substr(w, 2)
		if (i > 1)
			result = result " "
		result = result w
	}
	return result
}

# main program, for testing
{ print capitalize($0) }

With this input data:

A test line with words and numbers like 12 on it.

This program produces:

A Test Line With Words And Numbers Like 12 On It.

11.6. Variables and Array Assignments		11.8. Group Listing of awk Functions and Commands