title: What does the "+" symbol mean on the left side of the R console?
body: <p>I have entered in code to plot a graph, but when I press <kbd>Enter</kbd> to execute the graph, it does not plot the graph. Rather, <code>+</code> symbols appear every time I press <kbd>Enter</kbd> to execute the command and plot the code.
  Now there is a long column of <code>+</code> symbols in my R consoles.</p>
  
  <p>Why is this happening and what can I do to prevent this from happening?</p>