About character strings
Formally speaking, a single character is a single symbol. For instance, this is a single character between the double quotes:
"R"
Luckily, R does not make a difference between single ' and double " quotes, the interpreter will recognize single queotes just as fine, and will immediately turn them into double quotes.
'R'
The only thing that you need to be aware of is that you cannot mix up single and double quotes.
"R' # !!! Not a complete expression
If you try to run this statement, then the interpreter will not consider this as a closed, complete expression. It will expect you to continue entering values, which is visible from the plus signs (+) at the beginning of the line, where the prompt should be.
If you ever see this unintentionally, then you either need to complete the expression by entering the closing member of the symbol pair, or you can cancel this statement with the ESC key. (or Ctrl+C in a UNIX terminal)
Characters vs. Character strings
When you include multiple characters between the quotes, then you have a string of characters or character strings:
"R is cool."
You can include anything between these without problems: including single quotes.
"R is 'cheeky'."
You can also include double quotes, but for that you have to use the so-called escape characters, which we will cover at a later point. We will also cover character vectors, which are built using individual character strings (values). But first, let’s examine what we can do with simple, single strings.