DRIVER.TXT

Universal Drivers for Telink, Minitel, Fido, FidoNet,
Sysop, and Rolodex.

T. Jennings 	27 Nov 84
		 7 Jul 87	_mbusy

	All IO drivers MUST conform to this standard. All software will do
screen, clock, and modem IO through these drivers.

GENERAL

	You should put certain functions into seperate files, along the
following guidelines. The reason is that some programs use only the screen
functions (Rolodex, etc) some use only the modem functions (ViaDev, etc)
and some use both (Fido, Telink, etc). Seperating them will allow not
loading the whole damn thing everytime.

	Also, lconout must be in a seperate file; sometimes it is necessary
to use the standard MSDOS lconout() so that redirection can still be used.
PLINK will complain about multiple defineds unless you seperate them.

	DRIVER.H defines the static variables that must be set. These are:


CRT Variables

int lines;	Number of lines on the screen, i.e. 24 for a
		24 line screen.

int cols;	The number of columns on the screen, i.e. 80
		for an 80 column screen.

int top;	A mistake, but this is the top line NUMBER. Zero
		is just about universal, though, if the hardware
		starts its line numbering at 1, set it to 1.

int bottom;	The last line NUMBER, i.e. if the first line
		number is 0, then for a 24 line screen this will
		be 23.


char ulcorner = '+';	These are the characters used in drawing
char urcorner = '+';	boxes on the screen. if DRIVER.H is used,
char llcorner = '+';	they have the indicated defaults.
char lrcorner = '+';	They can be changed at init() time.
char vertbar = '|';
char horizbar = '-';

char graph_on[];	These are null terminated strings, used to
char graph_of[];	enable and disable graphics mode. If they are 
			not null, then they are sent out before any 
			attempts are made to draw the graphic 
			characters above. These must be set at init() 
			time.


MODEM PARAMETERS

unsigned cd_bit;	A bit mask for the modem input status
			function. This should be used by the
			_dsr() function (below) for testing
			for Carrier Detect. It is set by the
			main() of the program, with some sort
			of default. If desired, the default can
			be changed by the driver at init() time.

TIMER PARAMETERS:

long millisec;		These are incremented as millisecond
long millis2;		counters. The resolution is 1 millisec;
			however, high accuracy is not required. For
			the IBM PC, 55 is added every timer tick,
			and is close enough. For a 10 mS timer tick,
			add 10, etc.

int seconds;		Incremented at the same time as millisec,
int minutes;		above. Seconds should run from 0 to 59, then
			be cleared to zero, and minutes incremented. 
			Minutes increments indefinitely; there is
			no hours counter.



FUNCTIONS:

scrinit()		Set all the abovementioned screen variables.
			This is always called before any screen
			access is done.

init()			Full hardware initialization. This sets up
			any interrupt structures, calls scrinit(),
			and performs any other initialization
			necessary to make the hardware usable. This
			should also raise the DTR line, if any 
			(described below). There is a matching 
			function, uninit().

			This should start the clock ticking, and the
			'minutes' variable incremented once per
			minute. See NOTES, below, on a function to
			perform this.

uninit()		Take down any initialization necessary before
			returning to DOS, such as clock interrupts.
			NOTE: This should NEVER disturb the current
			state of DTR. This is to allow one program
			to terminate, and take control of the modem,
			without losing carrier. See NOTES on taking
			down the clock.

baud(rate)		Set the baud rate of the serial port or
			modem. 'rate' is the desired baud rate; it
			returns the baud rate set, or zero if that 
			rate is not supported.

_mconstat()		Returns 0 if no character ready at the modem,
			else any non-zero value. Do not remove the
			character from the modem. Non-destructive
			reads are performed at the next highest layer.

_mconin()		Returns the contents of the modem data port. 
			Wait for a character if necessary. Must return
			an 8 bit value.

_mconostat()		Return true if the modem is ready to accept
			a character.

_mconout(c)		Output character 'c' to the modem. Wait for
			output ready if necessary.

_cd()			Return true if CD is
			true. This reads whatever status port, masks
			it with the cd_bit value, and if true, returns
			true. 
			
lower_dtr()		Drop a modem output control line. The
			actual line used depends on the hardware.

raise_dtr()		Raise a modem control line. This also
			depends on the hardware. It should be
			called by init().

_mflush()		Flushes both (if any) input and output
			buffers.

_mbusy()		Returns true if there is anything in the
			output buffer; ie. returns zero when the
			output buffer is empty.
			If there is no output buffer, then this
			can return zero immediately.

_mbreak(n)		Set a line break (n != 0) or remove a line
			break. (n == 0). 


TIMER FUNCTIONS:

set_clk();		Start the timer running, and incrementing
			the TIMER PARAMETERS, mentioned above.

clr_clk();		Clears all of the timer counters to zero;
			millisec, millis2, seconds, minutes.

reset_clk();		Removes the clock timer.


CRT FUNCTIONS:


_lconout()		Optional function. The default one is in the
			XENIX library, which goes through the DOS.
			Create this one for custom applications
			or raw speed.

			Note that MSDOS redirection cannot be used
			if this function is invoked. If redirection
			is needed, write an _lconout() in the main
			function, that uses MSDOS calls.

place(line,col)		Place cursor at the specified line and 
			column. Input has already been bounded and 
			error checked; code for speed. The passed
			line number starts at 0 (top of screen)
			and columns start at 0 (left edge of screen.)

			Avoid the use of printf(), etc, or anything 
			else in "higher" level libraries. Use the 
			local _lconout(), as this function wont be 
			used if the program can use redirection.

clreol()		Clear from current cursor position to end 
			of line. Do not move the cursor. 

insline()		Insert a blank line at the current cursor
			line, and scroll the line under the cursor,
			and all below it, down one. The inserted
			line does not have to have any specific 
			contents. Code for speed.

delline()		Delete a line at the current cursor line.
			The line under the cursor disappears, and
			all lines below it scroll up one. The 
			bottom line does not have to be cleared.