You launch the Debugger by selecting the desired source file and issuing the Debug command as explained in Running or debugging a program.
When you launch the Debugger, you may see either or both of two prompts:
A dedicated OpenEdge runtime instance starts for the session in a suspended state, with an ABL stack trace displayed as a tree in the Debug view. The current line, which is the first executable statement in the source file, is selected in the stack trace. In an ABL Editor window showing the source file, this line is highlighted and includes an execution pointer () in the left margin.
Use any of the program execution commands on the Debug view toolbar or context (right-click) menu to proceed.
Debugging class files
When you use an ABL class file as the starting program for the Debugger, a temporary program is created to instantiate the class, using a public default constructor (no parameters). A different temporary program is used for each debugging session, as concurrent debug sessions are allowed. Each temporary program has a unique name relative to the Debugger session. If the class does not have a public default constructor, an error occurs.