Keywords: gildas-prog

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# Basic Routines

1. `LOAD_GREG (Mode)`
   To be updated since the change of SIC initialization mode This subroutine must be called before any other reference to GREG services. It is used to define the operating mode and to initialize the GREG vocabulary into the SIC monitor. The argument is of type Character and can be `'LIBRARY'` to initialize GREG in the ``Library Only'' (no interactive SIC monitor) mode, or `'INTERACTIVE'` to initialize GREG with all SIC monitor capabilities. Strings like `'LIBRARY GREG1'` or `'INTERACTIVE GREG2'` can be used to load only one language, although the GREG2 language requires GREG1 to function. This routine does not set the SIC prompt, neither the Log File which you may specify by calling routine `SIC_OPT`. Please refer to the SIC manual.
2. `GR_EXEC(LINE)`
   This is the basic routine for all plot actions. It is able to activate any GREG command exactly in the same way as if you had typed it during an interactive session. Use `GR_EXEC` if you do not know to which of the GREG languages it pertains, `GR_EXEC1,2 or L` according to the language if you know (and you should). The command line must not include the language field. The command is not written to the SIC stack, neither to the Log File.
3. `GR_ERROR()`
   This logical function allows error recovery. It returns the internal error status of GREG program, and clears it. If another GREG subroutine is called while an error status exist, program execution aborts.
4. `EXEC_GREG(LINE)`
   Obsolescent, use EXEC_COMMAND or EXEC_PROGRAM instead execute a command line which can be either a GREG command or a SIC command (like `'@ PROC'` for example). Control returns to the calling program when the command is completed successfully. If an error occurs, the current SIC error recovery action is activated before. This is usually a `PAUSE` which gives interactive control to the user ; control will then return to the calling program only after command `EXIT` (or `^Z`) has been typed. Contrary to `GR_EXEC`, the command is written to the SIC stack, and to the Log File. ``Interactive'' mode is required.

Only `GR_EXEC` (or its variant) and `GR_ERROR` are allowed in Library Mode.

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