Multi-Tasking

Here is an example of a boot menu, demonstrating a very simple version of this technique:

E> Do
    Screen Open 0,640,200,4,Hires
    Repeat
    Input "Please enter a program name to run: ";P$
    Exit If P$="",2
    Trap Prun P$
    If Errtrap : Print "Program not found!" : End If
   Until Errtrap=0
   Wait 50
  Loop

• You may use PRUN to call and run as many programs as memory allows.
• If there is a SYSTEM instruction in a program called by PRUN, it will not return to the Workbench, but back to the previous program.
• PRUN will work with compiled programs in exactly the same way as outlined above, except there will be no ".AMOS" appended to the name of the program that is to be loaded and run.
• The COMMAND LINES reserved variable can be used to send parameters between programs.
• The BGRAB command can be used to grab banks from the original program to the program that has been called.
• If an error is encountered during testing or running, a value will be stored in the PARAM function, as follows: <0 if there is a test-time error, >0 if there is a run-time error and zero if no error is encountered at all.

If you are not sure about the display before calling another program with PRUN, simply close all current screens. This will also free as much memory as possible. Similarly, if you are not sure about the display after running another program with PRUN, you should also close all of the screens, and then call the main screen initialisation of your original program again.

PRG UNDER
function: report the availability of a program "under" the current program
status=Prg Under

This function is used to report on the accessibility of an AMOS Professional program that is "under" the current program. One of three values can be returned:

Zero indicates that the current program is running normally, under the control of the Editor. Remote editor commands and BGRAB cannot be used.

A value of 1 indicates that the current program is the only program running, but it is not the program currently under the control of the Editor. This happens when an accessory program is run or a "program to menu" option is selected, and remote editor commands are allowed as well as the use of the BGRAB command.

A value of -1 means that the program has been run via another program, using PRUN. In this case, memory banks can be grabbed, but remote editor commands cannot be sent.