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Text File | 1991-10-27 | 18KB | 475 lines

--------------------------------------------- * MultiDos Plus Rel. 4.01 Shareware Version * * Copyright (c) 1986 - 1991 Nanosoft Inc. * --------------------------------------------- Welcome to MultiDos Plus, a powerful real-time multitasking shell for DOS. MultiDos Plus is a copyrighted work of Nanosoft Inc and is NOT public domain. If you like this product, register with us for $35, and we will send you the commercial version of MultiDos Plus ($99 value) with printed documentation. You may freely copy and distribute this product as long as you abide by the following conditions: a) You may not charge any fee for making copies or sell this product. b) You may not distribute this as part of any product or service for which you charge a fee. c) You must copy the product in its entirety with no changes. If you would like to do any of the above, you must have our permission in writing. Contact us for site licensing and royalty arrangements. ------------ * WARRANTY * ------------ This product is distributed with absolutely no warranty of any kind. ------------------- * How to Register * ------------------- Send a check for $35 to: Nanosoft Inc. 13 Westfield Road Natick, MA 01760 Attn: Shareware Dept. To register using Mastercard or Visa call (508) 651-0091. To register by FAX send name, address, and charge card information (be sure to include expiration date) and telephone numbers to (508) 655-8860. ------------------------------------------------------------- * Differences between the commercial and shareware versions * ------------------------------------------------------------- The commercial version which you will receive when you register has the following additional features: a) It supports 64 tasks instead of the 3 tasks supported by this version. b) The commercial version supports programs running in LIM 4.0 expanded memory. This version supports progams running in conventional memory only. The documentation accompanying this product is for the commercial version. Therefore, disregard all references to expanded memory and related commands. ----------------------------- * To install MultiDos Plus: * ----------------------------- Print the file MDSHARE.PRN and read it before using Multidos Plus. For a quick start type MULTIDOS to start the program. When it is up, type a ? for a brief list of commands. The following is a list of new features or information not found in the manual. Read the manual first before reading the following sections. -------------------- Command Line Options -------------------- A new command line option has been added which tells MultiDos Plus not to load the MDBIO10.EXE display BIOS. This option may be invoked by typing /NO10 on the MultiDos Plus command line. For example: MULTIDOS /NO10 This option is useful for applications which only have one task which will ever write to the display. It may also be useful if your tasks cooperate with each other in their use of the display by using a resource semaphore to control display usage. Please note that RS-232 output redirection is performed by the MDBIO10 module. If your application uses the COMM command to specify I/O redirection, the /NO10 option will disable the redirection of the display output. *** /NOMAP *** A new option is available to disable the mapping of LIM memory into empty spaces above the C000 segment. Use /NOMAP to disable the mapping. *** /NOCB *** A new option is available to disable the checking for CTRL-C and CTRL-BREAK during DOS writes. Use /NOCB to completely disable the checking for these two key combinations. If this option is not used and a CTRL-C is pressed during a DOS write to the CRT display, the application may be aborted, or if if has an INT 23H handler that ignores CTRL-C or CTRL-BREAK, an ugly unexpected ^C may be displayed. Using /NOCB makes it possible to use the ANSI.SYS functions to format and control a display without risking that the operator may enter a CTRL-C during a DOS display write. ----------------- Operator Commands ----------------- * ASG Command * MultiDos Plus has a feature which will enable certain keys to bring a task to the foreground immediately without using the ALT Z sequence. The PC keyboard function keys and ALT keys may be used for this purpose. For example, the F1 function key may be set to always bring the COMMAND task to the foreground. Once a key assignment has been made, the task may be brought to the foreground any time the key is pressed. The way to make this assignment is to use the ASG command. The ASG command allows the assignment of up to 10 keys to 10 tasks. The syntax for the ASG command is: ASG [<task name> <index> <scan code>] If the ASG command is entered without any arguments, a list of current key assignments will be displayed. Each of the 10 entries in the assignment table is listed in the order: index, scan code, task name. The arguments specify a mapping between a specified scan code and a task name. The scan code must be specified as a decimal number. The ASG command to map the COMMAND task to the F1 function key would be: ASG COMMAND 0 59 This command would set the first entry in the assignment table to map the task COMMAND to scan code 59 which is the F1 function key. The decimal values for the function key scan codes are: Key Normal Shifted Ctrl Alt F1 59 84 94 104 F2 60 85 95 105 F3 61 86 96 106 F4 62 87 97 107 F5 63 88 98 108 F6 64 89 99 109 F7 65 90 100 110 F8 66 91 101 111 F9 67 92 102 112 F10 68 93 103 113 The scan codes for other function keys and the Alt keys may also be used. If an astrisk is used in the place of a task name, the key assignment has a different meaning. Whenever that key is pressed, the previous foreground task is brought back to the foreground. For example: ASG * 0 61 Whenever the F3 function key is pressed, the previous foreground task will be brought back to the foreground. The value after the task name is the assignment table index and can range from 0 to 9. Entries may be placed in any order in the table. When a key is pressed, the entry with a matching scan code closest to the begining of the table is used. The /NALTZ command line option will not disable the single key task selection feature. * BAT Command * The BAT command will tell MultiDos Plus to execute commands from an ASCII text file as if they were entered from the keyboard. The format is: BAT filename where filename is any DOS pathname. All commands in the file are executed by MultiDos Plus before any other commands (i.e. INT 15H, function 15) are executed. No other task's child process requests are processed until the BAT command is finished. A BAT batch file can also contain embeded batch commands. * FG Command * A feature of the FG command, missing from the manual, is the ability to bring the previous foreground task back into the foreground without having to know the task's name. If an astrisk is used in place of the task name, the previous foreground task is brought back to the foreground. This function is most useful when a task is done with the foreground and wants to switch itself to the background, restoring the task that was previously in the foreground. The task can submit an FG command, using INT 15H function code 15, to MultiDos Plus. * REM Command * A command has been added to allow the addition of remark statements to automatic startup files. The REM command may be added to document the content of the file. Any characters after the REM are completly ignored. The following are examples of some REM statements: REM This is a test REMthisisatest REMARKABLE application written by Jack Spratt ----------------------------- Application Program Interface ----------------------------- Several additional functions have been added to the Application Program Interface. * Return Memory Parameters * Function code = 31 Entry: AH = 31 Exit: BX = First memory segment of conventional memory DX = First memory segment of the LIM swap frame created by MultiDos Plus to load programs into * Test if Multitasking is Disabled * Function code = 32 Entry: AH = 32 Exit: AX = 0 if multitasking is enabled or AX = TCB of task that disabled multitasking This function may be useful by interrupt handlers which may need to know if multitasking is disabled or not. ------------------------------------------- IRQ Enhancement for LIM Tasks ------------------------------------------- The IRQ command has been enhanced to support programs with interrupt service routines in swappable LIM memory. This includes many of the off-the-shelf communication programs as well as many other types of programs. The enhancement added a new command line optioin and two additional MultiDos Plus commands. The /IRQ command line option is used to enable the new features. If MultiDos Plus is invoked without this option, the IRQ command functions as documented in the manual. The /IRQ option must be followed by a hexadecimal value between 78 hex and F0 hex. This option can only be used on AT type computers. The /IRQ will tell MultiDos Plus to reprogram the 8259 interrupt controllers to use the specified vectors rather than the standard vectors. MultiDos Plus will then intercept all the hardware interrupts and re-vector them thru the original vectors. This allows MultiDos Plus to check if the interrupt has been associated with a task executing in swappable LIM memory and if so, map the task in before vectoring to the old vector. When the old vector ISR has finished processing, it returns to MultiDos Plus to restore the interrupted task's memory context. If the /IRQ option is used, the MultiDos Plus IRQ command is used to associate a hardware interrupt to the next loaded task. For example, suppose you want to run PROCOMM in LIM memory and using a modem connected to COM1. You also determine that nothing in your system uses the interrupt vectors 80H thru 8FH. MultiDos Plus is invoked by entering: MULTIDOS /IRQ 80 At the $ prompt enter the following commands: RM 300 (assuming your version of PROCOMM only needs 300K) IRQ 4 (COM 1 is IRQ 4, COM 2 is IRQ 3) PROCOMM (assume in your current directory) PROCOMM will be loaded in a 300K block of memory and will be associated with IRQ 4 (INT 0CH). Two additional commands have been defined to associate or disassociate IRQs with tasks that have already been loaded. These commands are SIRQ to associate and CIRQ to clear an association. The SIRQ command will allow the association of more than one IRQ to a task. The format for the SIRQ command is: SIRQ task irq# and the CIRQ command is: CIRQ irq# If an IRQ is already associated with a different task, SIRQ will issue an error message. The assignment of IRQ 0 is not permitted. When a task terminates, all IRQs associated with the task are cleared. --------------------------------------------- Application Interface for Task Context Switch --------------------------------------------- In order to provided our customers with high performance multitasking, the task context save and restore procedures save only the most necessary context required by most tasks. Some applications may require that certain other context be preserved at every task switch. An example might be several tasks which make use of the 8087 coprocessor. Although the coprocessor can be treated as a resource and controlled with a semaphore, this may not be feasable (lack of source code) or practical (complex calculations in pre-existing software). Another example might be the saving and restoring of a software interrupt needed by several tasks running in LIM memory. An interface has been developed which allows applications to get involved in the task context switch process. It is possible to set the entry point for two routines, one to save context and the other to restore context. The routine to restore context will be executed just before a task is allowed to run and the routine to save context will be executed when a task's execution is suspended (end of timeslice, give up timeslice, read keyboard, suspend for interval, etc.). The two routines are global. e.g. All tasks must use the same routines. Since some tasks require certain context be preserved and others do not, a flag mechanism exists to inform the context save and restore routines if and what context, if any, should be saved/restored. A new command, MISCFLAG, has been added which is used to set bits in the MISCFLAG word (byte offset 200) in the TCB. The format of the command is: MISCFLAG <hex value> The <hex value> is masked with hex 7F to keep only the lower 7 bits and is placed in the upper byte of the miscellaneous flag word when a task is first loaded. In other words, this command must be issued just prior to loading a task. When MultiDos Plus saves or restores a task's context, the value specified by the MISCFLAG command is checked for non-zero. If no MISCFLAG command is issued prior to a task load, the default value is zero. If a non-zero value is found, the application supplied context routines are executed. As stated earlier, the context save and restore routines are global and should probably be written as a TSR which must be executed under MultiDos Plus and must be installed in conventional memory. A sample TSR is supplied named APPLCTX.ASM to save and restore floating point context for a real 8087 and/or Microsoft floating point emulation. The TSR initialization code informs MultiDos Plus of the two routine's entry points by issuing a special INT 15H API call. The following code fragment can be used to set up the entry points. It assumes that the context save/restore routines are in the same code segment as the code fragment. MOV AX,1E08H ; FUNCTION AND SUBFUNCTION CODES PUSH CS POP DX ; SEGMENT OF ROUTINE CODE MOV BX,OFFSET CTXSAVE ; OFFSET OF CONTEXT SAVE ROUTINE MOV CX,OFFSET CTXRSTR ; OFFSET OF CONTEXT RESTORE ROUTINE INT 15H When either the save or restore routine is entered, ES:BX will be pointing to the task in question's TCB. Care must be exercised not to destroy any registers. When the routine is finished it must use a far return to return control to MultiDos Plus. The save and restore routines can be removed from execution by executing INT 15H function 1E08H and setting the save and restore routine entry points to null (0000:0000) pointers. A new field has been added to the TCB to aid the context save/restore routines in indexing into their context tables. The word at byte offset 220 in the TCB has the TCB index which is a value from 0 to the number of TCBs - 1. If the default number of TCBs (12) is configured, the largest TCB index will be 11. If you are trying to execute several BASIC programs, you may wish to use the APPLCTX TSR as most BASIC's use floating point. Other possible context save/restore needs might be the 32-bit registers in a 386 or the GDTR, LDTR, IDTR, etc. This should allow the execution of multiple DOS extenders or 32-bit software. -------------------------------------------------------------------- P E R F O R M A N C E -------------------------------------------------------------------- If MultiDos Plus is used in an application where you have complete control of the source code, here are several tips which can be used to help you gain the maximum possible performance from the hardware which will be running your software. Keep in mind that if a task waits for a key from the keyboard, waits for a message from a message queue, waits for an event, or waits for control of a resource semaphore, the task will not receive any time until a character, message, event or control is received. This gives more time to other running tasks doing useful work. Use the API function to give up your timeslice (AH = 0) where ever possible. This function will allow another task to have a chance to run if the current task has no useful work to perform for the rest of a timeslice. For example, if a task was displaying the current time on the display and checking for a keyboard input, it should give up its timeslice at the end of the loop if no keyboard input was received. In addition, only get and check the time as often as realistically required. There is no need to update the time display 18 times a second if the resolution is in minutes! If you are using the /PR scheduling option be sure to use the API function to suspend a task (AH = 3) in order to give up a timeslice. Use of the API function (AH = 0) to give up a timeslice under this scheduling option may prohibit tasks of a lessor priority from executing because execution is given to the highest priority task in the READY queue. If the default scheduling is used and you are setting different task priorities, be sure at least one task has a priority of zero. This will insure the maximum possible performance from the scheduling mechanism. If you don't need the ANSI.SYS emulation for a task, turn it off using the NANSI MultiDos Plus command. This will eliminate the overhead associated with this feature. If a task will never use the display, use the ND command prior to loading the task .EXE or .COM. Be sure to use the XQ command to start execution immediately after the task is loaded. If your application only requires a single task to write to the display, use the /NO10 option to inhibit the loading of the MultiDos Plus BIOS INT 10H replacement (MDBIO10.EXE) which would not be necessary. This would eliminate additional overhead when writing to the display.