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System
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System
Appendix D: System
The Mesa system is available as Mesa.image. Users without need of some of the runtime machinery (BasicMesa users of earlier systems) can trim down the Mesa system via a command line switch. Support for use of memory banks other than the first is part of the standard system (provided that the proper microcode is available on the machine running it). The standard user interface is the command line; BCDs are loaded and started by specifying them on the command line. It is also possible to load the Mesa Executive which serves as an interactive user interface.
Command Line Loading
Client BCDs are loaded by specifying them on the command line. The general form of the command line is:
>[Mesa[/d]] [/s] file1[/s] file2[/s] . . .
The valid global switches are listed below. A ’-’ preceding the switch inverts its meaning.
/b -- convert the system to a "basic" one. Throw away the keyboard and display handlers, close Mesa.typescript.
/d -- go directly to the debugger (this is the only switch applicable to the image file).
/k -- don’t allocate the debugger bitmap in bank 1 (see Appendix E: Debugger)
The valid local switches are listed below. A ’-’ preceding the switch inverts its meaning.
/d -- go to the debugger after loading this BCD but before starting it.
/s -- start the BCD (default if non-null control module).
/l -- load the BCD with code links. The modules will only have code links if there is room for the links in the code and the modules specify that they want code links. See Appendix D of the Mesa Language Manual for a discussion of code links.
The default extension for file is ".bcd". The Alto Executive inserts Mesa.image (if it’s on the disk) in front of files ending with the extension .bcd. Global switches are given by a slash with no preceding file name. Local switches apply only to the file to which they are attached. If Mesa runs out of things to load from the command line, it returns to the Alto Executive.
Feedback of modules loaded and their global frame address is given on the screen and on the file Mesa.typescript unless the /b switch is invoked.
Example:
>Mesa DisplayPackage/l-s SomeConfig/d
Start Mesa and load the DisplayPackage with code links but don’t start it. Then load SomeConfig and go to the debugger before starting it.
Restrictions
The default maximum number of processes is 75. The default number of modules is 384. If this is too large, there is SmallMesa.image with 32 and 256 respectively. If this is too small, negotiate with your support group to have a larger Mesa system made.
Mesa Executive
An interactive user interface can be obtained by loading the file MesaExec.bcd into Mesa.image. It provides commands for loading and starting modules, going to the debugger, and exiting to the Alto Executive. The commands are given as single letters, and are completed to full words by the program. The prompt is a ">". All characters typed on the screen are also written into the file Mesa.typescript.
Commands
Below is a listing of the commands with the characters typed by the user underlined.
>New Filename: file[/l]CR
Load file into the system but don’t start it. A file extension of .bcd is assumed. MesaExec then prints out the global frame address for the module (or control module of a bound config). The optional /l instructs the loader to use code links if space is provided for the configuration being loaded.
>Start Global frame: numberCR
Start the (or restart) module with the given global frame. Typing ESC to the prompt will insert the global frame address of the last file loaded via New.
>Debug [Confirm]CR
Go to the Debugger (if installed). Proceed from the Debugger to return to MesaExec.
>Quit [Confirm]CR
Return to the Alto Executive.
>-- any text CR
Insert a comment into Mesa.typescript.
Error Messages
Errors generated during loading or interaction with the Mesa Executive are reported by displaying messages. If there is no display (e.g., you said /b), Mesa generates signals that will be caught by the debugger. The following error messages are given by the Mesa Executive:
!File: file
When attempting to load a Bcd, file cannot be found or is an invalid Bcd. If file is not the Bcd being loaded, then it is a code file for the Bcd. A Bcd may be invalid because it was produced by an incompatible version of the system.
!Number
An invalid number was typed.
!String too long
A string was typed that was too long.
!File name referenced in different versions
When loading a Bcd, the interface or program name was referenced in different versions. Loading is continued but there may be unbound external references.
External Debugger not installed, type DEL to abort
An attempt was made to invoke the debugger but it has not been installed.