Appendix C. Operating System Calls
The computer's Operating System is a program, stored in read-only memory, which runs continually, sorting out what goes where and when. Some parts of the Operating System can be accessed from BASIC, and these instructions all begin with an asterisk. When executing BASIC, the computer will pass these instructions straight to the Operating System.
Here is a list of available commands:
*CAT
Catalogues all file names on cassette, and displays them on the screen. Can be shortened to *.
*SAVE
Saves a section of memory onto tape. *SAVE "File" 1000 10FF 102A will save a page of memory, called File, from address &1000 to &10FF, and an execution address (for use by *RUN) of 102A. If the execution address is omitted, it is assumed to be equal to the start address.
*RUN
Loads and runs a program stored by *SAVE. *RUN "File" will load and run the example given in *SAVE above.
*LOAD
Loads a file and stores it in memory at a specified address. *LOAD "Game" 2000 will load from tape a file called Game, and store this at location &2000.
*OPT
Determines the computer's reaction to errors during cassette operations.
*OPT1,X Controls the error messages given.
| X=0 | Gives no messages. |
| X=1 | Gives short messages (as normal). |
| X=2 | Gives long messages, including load and execution addresses. |
*OPT2,X Controls the computer's action.
| X=0 | Lets the computer ignore all errors, and carry on regardless. Messages can still be given. |
| X=1 | The computer asks you to try again by rewinding the tape (as normal). |
| X=2 | The computer aborts the operation. |
*OPT3,X Sets the inter-block gap - the time delay between each page of memory stored on the tape. X determines the gap in tenths of a second. This only applies to PRINT# and BPUT#. The gap on SAVE is fixed at 0.6 seconds.
*OPT On its own sets all the values to normal.
*SPOOL
Used for saving a program listing or results (as long as they are ASCII characters) to cassette or disc as a text file. Thus *SPOOL FRED opens a file called FRED on either tape or disc. Whatever characters appear on the screen after that (e.g. a program listing called up by LIST, or one you enter on the keyboard) will be saved to FRED as a text file. To close the file, type *SPOOL RETURN at the end.
*EXEC
Loads a file from tape, as input rather than as a program. Used for loading a file which has been *SPOOLed.
*MOTOR
Used to turn the cassette motor relay on or off. *MOTOR0 for off, *MOTOR1 for on.
*KEY
Programs a user-definable function key.
*FX
A family of Operating System commands which are described in Appendix D.
*HELP
Gives version numbers of current software.