Using the Line-Number Region

The line-number region shows the line numbers associated with the source code displayed in the source window. Figure 2-3 shows a portion of a line-number region, with a breakpoint set.

Figure 2-3 Line Number Region

You will see the following symbols in the line-number region:

• The > symbol in the line-number region in Figure 2-2 is the execution pointer. When the program is being executed, the execution pointer points to the next line to be executed, for the most-active function call; or to the call site for functions higher on the stack. If you move elsewhere in the source code, typing Control-x returns to the current execution point.

• A B appears in the line-number region next to every line at which execution is to stop. You can set simple breakpoints directly in the line-number region; all methods for setting breakpoints are described in " Setting Breakpoints".

• A T appears in the line-number region next to a line for which Prism is tracing execution. See " Tracing Program Execution" to learn how to trace program execution.

Shift-click on B or T in the line-number region to display the event associated with the breakpoint or tracepoint. See " Overview of Events" for a discussion of events.

The display of breakpoints and tracepoints in the line-number region is slightly more complicated in MP Prism; see " Using the Line-Number Region in MP Prism".

• The - symbol is the scope pointer; it indicates the current source position (that is, the scope). Prism uses the current source position to interpret names of variables. When you scroll through source code, the scope pointer moves to the middle line of the code that is displayed. Various Prism commands also change the position of the scope pointer.

• The * symbol is used when the current source position is the same as the current execution point; this happens whenever execution stops.

If you right-click in the line-number window, you display the source-window pop-up menu discussed in the previous section. Right-click anywhere in the main Prism window to close this menu.