Line breakpoints are set on an executable line of a program. To set a line breakpoint at a line of source code:
A breakpoint appears in the Breakpoints view. A breakpoint icon appears on the marker bar, directly to the left of the line where you added the breakpoint. The line where the breakpoint is set is highlighted in the editor area. The line appears highlighted in the C/C++ perspective also.
When the breakpoint is enabled, the thread execution suspends before that line of code executes. The debugger selects the suspended thread and displays it's stack frames.