Often we need to deal with the individual characters in a
string. We might want to check to see whether a
string contains any whitespace, or to change the characters to lowercase, or to see whether a given character is present, and so on.
One part of this kind of processing involves how we gain access to the characters themselves. Sometimes we need to process every character. Other times we need to process only a specific character, or we can stop processing once some condition is met. It turns out that the best way to deal with these cases involves different language and library facilities.