After a code editor, the debugger is probably the tool used most often by a developer. Most IDEs will include a source code debugger. The debugger allows you to view the source code of a program as it is being executed by the compiler. Common operations of a source code debugger include:
single stepping through code, executing a single line of code at a time
the ability to single step into a function call, or simply to single step over all statements in a function without following function calls
the ability to set breakpoints at any line or function in the source code
the ability to set a breakpoint based on an arbitrary code expression
the ability to set and display variables in the program, including complex structures
the ability to view the call stack
a disassembler