A string is a kind of array, namely, an array of characters. A string has properties that a simple array of characters lacks, but you can still refer to the characters within a string using array notation. Now a string of length 1 and a character are indistinguishable for most purposes. But starting with version 4.0, TP has used very strict type-checking for the sake of speed and efficiency. This gives us a quick way to change single characters inside strings.
Copy leaves String intact.
Delete alters String. If 'test' does not occur in String, Pos returns 0. The plus sign can join string variables or tokens, or mix strings with characters and packed arrays. Expect strict type-checking, for example between characters and strings of length 1. ShortString is a syntax error.