Customization of the CCP.




		The standard CP/M-68K CCP contains four different program

	modules.  In order to write your own customized version of the CCP

	it is only necessary to substitute your CCP for two of the four

	existing modules.  However it is essential to understand the inter-

	facing procedures between the four different modules and their relation-

	ship to the BDOS and BIOS of CP/M-68K.


		The four CCP program modules are:

		(1)  CCPIF.O		

		(2)  CCPBDOS.O

		(3)  CCPLOAD.O

		(4)  CCP.O


		The first three modules of the CCP perform general CP/M

	housekeeping functions.  CCPIF.O is the coldboot and warmboot interface

	between the CCP,the BDOS,and the BIOS.  CCPBDOS.O is an assembly

	language module that performs the BDOS function calls for the main

	CCP module:  CCP.O.  CCPLOAD.O is the assembly language module that

	performs the program load function for CCP.O.  CCP.O is the main module

	of the CCP.  Substitute your custom CCP for modules three and four of the

	standard CCP for CP/M-68K.  A description of the CCP input and output

	interface requirements with modules one and two as well as the BDOS

	and BIOS follow.

	CCP INPUT INTERFACE
	-------------------

		The main module of the CCP is entered via a jsr(jump to sub-

	routine) instruction from CCPIF.O.  Here is the exact instruction as

	it appears in CCPIF.O.


		jsr	_main		*call the CCP


		The label _main contains the underscore character because

	the C compiler places an underscore before every external variable

	and function name.  CCP.O contains the function:

		main()
		{
			/* main CCP module */
		}

	which orchestrates the function of the Console Command Processor.

	This jsr instruction is the only entry point to the CCP.


	CCP OUTPUT INTERFACE
	--------------------


		The CCP needs to access the BDOS to perform its function.

	The module CCPBDOS.O contains assembly language instructions to

	fill registers D0 and D1 with the BDOS function number and the BDOS

	parameter respectively.  This module is expecting to pull off the

	stack a word for the function number and a long word for the parameter.

	The function is defined in the main module as follows:
		
		EXTERN UWORD bdos();

	Here are two examples of the CCP.O to CCPBDOS.O interface:

	(1)  userno = bdos(GET_USER_NO,(long)255);

	(2)  move.l	#255,-(sp)
	     move.w	#GET_USER_NO,-(sp)
	     jsr	_bdos
	     tst	d0		*return value in register D0
	     move.w	d0,userno	*get return value	
		etc.......			

	The bdos will return a word value for the current user number.

		In the standard CP/M-68K CCP,a warmboot occurs after the

	termination of every transient program.  Upon warmboot,control is

	transferred to the BDOS and eventually back to the CCP via that

	jsr instruction.  Before entrance to the main module,the system

	stack is reset to its orginal starting address.  CCPIF.O must be

	the first module of CP/M-68K.  This module also performs coldboot

	startup procedures essential to coldboot loading.  Any interface

	to the BIOS is done through the BDOS direct BIOS call.  See the 

	programmer's guide for details.  If you experience problems with

	doubly defined global variables,use the NM68 utility to get a listing

	of the system symbol table.  For example:

				A>NM68 CPM.REL

	will give you a listing of the CP/M-68K symbol table.  For further

	details regarding the use of NM68 see the CP/M-68K programmer's guide.

		Finally it is necessary that the CCP use bdos function 10 to

	read in a command line from the console if you wish to make use of

	bdos function 47(chain to program).  The chain to program function

	traps function 10 calls and supplies the CCP with the next command

	to execute from an internal buffer.