# Development Tools

Writing and Modifying Program Code |

While PxPlus allows external methods for writing source instructions, a program cannot be converted to tokenized code and executed unless it exists within an active PxPlus session. In Command mode, the current program represents all the statements in memory that are immediately available for editing and/or execution. In Execution mode, the current program is also called the main-line program (execution level 1).

Whether you create a new program or LOAD an existing program, the changes you make to numbered statements at the command line apply to the current program in memory.

#### Note:
The current program does not have to be saved to be RUN. Conversely, saved program files can be run directly without first being loaded, although the RUN will automatically load the specified program if not already loaded.

PxPlus programs can be edited using a variety of techniques, including the *IT - Integrated Toolkit, Ed+ program editor, Command line editor, *E character-based editor, as well as any other text editor that saves source code in ASCII format.

## Numberless Programs

Line numbers are considered optional in PxPlus. However, numberless programs can only be created using the PxPlus graphical user interface based program editors, *IT and Ed+, or some other text editing tool (because non-numbered statements would be executed immediately at the Command line).

Once created, a numberless program may be loaded and listed (and edited) in Command mode. When issuing a LIST of a numberless program, sequential line numbers will be inserted automatically (for reference/editing purposes).