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NANSI.SYS
An Enhanced MS-DOS Console Driver
Version 3.4 November 1991
Documentation updated February 1999
http://alumni.caltech.edu/~dank/nansi/
1. Introduction - Who should use NANSI.SYS
NANSI.SYS is a console device driver for MS-DOS computers. It exe-
cutes the same ANSI cursor control sequences as does the standard con-
sole driver ANSI.SYS, but significantly faster. It also offers
several extra features, while still being simple, small, and cheap.
You can benefit from using NANSI.SYS if:
1. you use programs (such as DIR, MORE, or NETHACK) which display text
on the screen via DOS, or
2. you have an EGA or VGA, and want to use the 43- or 50-line mode of
your display, or
3. you run out of space when redefining keys with ANSI.SYS, or
4. you are a programmer who uses ANSI escape sequences, and are frus-
trated with slow display updates, or
5. you are porting display-intensive Unix programs to run under MS-
DOS.
You will not benefit from using NANSI.SYS if:
1. you never wish commands like TYPE or DIR were faster, and
2. you only use programs like Microsoft Word or Word Perfect, which
bypass DOS when displaying text, and
3. you aren't interested in displaying 43 lines of text on your EGA or
VGA, and
4. you have never heard of ANSI.SYS anyway.
The display speed improvement you get by installing NANSI.SYS depends
on the kind of programs you run. Installing NANSI.SYS will bring no
improvement in display speed for programs that bypass DOS (e.g. Micro-
soft Word), a 30% improvement in display speed with most programs that
don't bypass DOS, a 50% improvement with "optimized" programs (see
chapter 9 below), and a 95% improvement with "optimized" programs that
avoid scrolling.
One "optimized" program, COPY /b, comes with DOS. To test the speed
improvement yourself, create a long text file named foo.txt, and
display it with COPY /b foo.txt con: with NANSI.SYS installed- it will
go by very quickly. This speed increase occurs even when running in a
window in Microsoft Windows 3.0.
2. Compatibility
NANSI.SYS has been tested on IBM PC/XT, /AT, and PS/2 systems. It
should run on any CGA, MDA, EGA, or VGA compatible video card. It is
compatible with Microsoft Windows 3.0. Unlike many display speedup
progams, it does not use wierd hardware scrolling tricks, and there-
fore remains completely compatible with programs that write directly
to the screen.
November 29, 1991
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3. Copyright status
This program and documentation is Copyright 1986, 1991 Daniel Kegel.
The executable program and its documentation may be freely distri-
buted.
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
or look on the web at http://www.gnu.org/copyleft/gpl.html.
Correspondence (in English, German, or French) should be
directed to the author at dank@alumni.caltech.edu
4. Version
The version number can be found with the DOS command TYPE NANSI.SYS.
This documentation is for version 3.3, created November 1991.
5. Installation and System Requirements
NANSI.SYS version 3.3 is distributed as the archive NANSI33.ZIP, with
the following contents:
NANSI.SYS - the device driver
NANSI.DOC - this documentation file
RAW.C - how to set and clear RAW mode for faster screen output
RAW.H - definitions for users of RAW.C
GC.ON - text file which, when TYPEd, turns on the graphics cursor
NANSI.SYS requires MS-DOS version 2.0 or higher, and uses about 3
kilobytes of system RAM.
To install NANSI.SYS on your computer, copy the file NANSI.SYS to your
boot disk (usually C:), and include one of the following statements in
the configuration file CONFIG.SYS on your boot disk:
For IBM VGA and Vega VGA cards, or if you don't know (or care) what
kind of card you have:
DEVICE=NANSI.SYS
November 29, 1991
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For Paradise VGA Plus cards:
DEVICE=NANSI.SYS /t54 /t55 /t56 /t57
For VGA cards using the Oak Technology OTI-067:
DEVICE=NANSI.SYS /t4F /t50 /t51
For VGA cards using the Trident Microsystems TVGA 8900:
DEVICE=NANSI.SYS /t50 /t51 /t52 /t53 /t54 /t55 /t56 /t57 /t58 /t59 /t5A
6. COMMAND-LINE OPTIONS
6.1. /K : force Nansi to use extended keyboard BIOS calls which
sense F11 and F12
When IBM introduced the extended keyboard with F11 and F12 keys, and
separated the numeric keypad from the arrow keys, it also introduced
an extended way of reading the keyboard with BIOS. The old way still
works, but doesn't recognize the extended keys.
Normally, Nansi tries to detect whether the extended keyboard BIOS
calls are available, and if so, uses them. However, by giving the /k
option you can force Nansi to use these calls even if Nansi doesn't
think they are there. This option is included for compatibility with
ANSI.SYS.
6.2. /X : tell Nansi to let you redefine the extended keys indepen-
dantly
IBM's extended keyboard BIOS calls added something new: they return
different scan codes for different keys with the same meaning. For
instance, they return 71 for the numeric keypad HOME key, but 224;71
for the gray HOME key. Nansi returns 71 when either of these keys are
pressed. However, the /X option causes these keys to be treated dif-
ferently during keyboard redefinition. For example, if you start
Nansi with the /X option, you can define just the gray HOME key to say
"dir/w" by sending the string ESC [224;71;"dir/w";13p
6.3. /S : tell Nansi to be secure, and disable keyboard redefini-
tion
Although it is nice to be able to redefine the keyboard with escape
sequences, it is a gaping security hole. To prevent trojan horse
attacks from messages in text files, archives, and programs downloaded
from the outside world, disable this feature by invoking Nansi with
the /s option in config.sys. For example,
DEVICE=NANSI.SYS /s /t54 /t55 /t56 /t57
This saves a few bytes of memory, too.
November 29, 1991
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6.4. /Tnn : tell Nansi that video mode nn is a text mode
No two VGA cards seem to have the same set of video mode codes. The
same mode number can indicate a graphics mode on one card, and a text
mode on another card. Worse yet, BIOS can't tell you what kind of
mode it's in. This is a problem because Nansi gets its speed by
bypassing BIOS, which it can only do in text modes.
Nansi solves this dilemma by maintaining a 256-entry table, one entry
per possible video mode. By default, the table says that only modes
0, 1, 2, 3, and 7 are text modes. You can add new text modes with the
/t option. For instance, if modes D hex and 50 hex are text modes,
you would invoke Nansi as follows:
DEVICE=NANSI.SYS /t0D /t50
How to tell whether you need /t:
If your board is in a non-IBM text video mode (for instance, mode 50
hex), and you haven't added /t50 after NANSI.SYS in CONFIG.SYS, the
cursor will disappear after a CLS command, and the text output will be
sluggish; furthermore, if you turn on the graphics cursor (by TYPEing
the file GC.ON which came with NANSI), the beginning and end of every
text line will be garbled.
How to tell whether you don't need /t:
If you mistakenly specify a graphics mode with the /t option, the
display will be garbled while in that mode. Get back to normal by
typing MODE CO80 or rebooting, and remove the offending /t option from
config.sys.
November 29, 1991
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7. ANSI Control Sequences
While putting text up on the screen, NANSI.SYS keeps a lookout for the
escape character (chr(27), known as ESC); this character signals the
start of a terminal control sequence. Terminal control sequences fol-
low the format
ESC [ param; param; ...; param cmd
where
ESC is the escape character chr$(27).
[ is the left bracket character.
param is an ASCII decimal number, or a string in quotes.
cmd is a case-specific letter identifying the command.
Usually, zero, one, or two parameters are given. If parameters are
omitted, they usually default to 1; however, some commands (KKR) treat
the no-parameter case specially. Spaces are not allowed between
parameters.
For example, both ESC[1;1H and ESC[H send the cursor to the home posi-
tion (1,1), which is the upper left.
In general, if you ask the cursor to go beyond the edge of the screen,
it goes to the appropriate edge. (ANSI.SYS was not always so nice.)
The following C macro illustrates how one could print a string at a
given location on the screen:
#define printXY(x,y,s) printf("%c[%d;%dH%s", 27, y, x, s);
Either single or double quotes may be used to quote a string. Each
character inside a quoted string is equivalent to one numeric parame-
ter. Quoted strings are normally used only for the Keyboard Key Reas-
signment command.
Each ANSI control sequence supported by NANSI.SYS is described below.
The descriptions follow the format
7.0.1. ABBREVIATED_NAME: what_to_send LONG NAME
where ABBREVIATED_NAME is a short name for the sequence, what_to_send
tells you what characters make up the sequence, and LONG NAME is a
long name for the sequence.
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7.1. Sequences dealing with Cursor Positioning
7.1.1. CUP: ESC[#;#H Cursor Position
Moves the cursor to the position specified by the parameters. The
first parameter, y, specifies the row number; the second parameter, x,
specifies the column number. If no parameters are given, the cursor
is moved to (1,1), the upper left corner of the screen.
7.1.2. HVP: ESC[#;#f Horizontal and Vertical Position
This is identical to Cursor Position. Don't ask me why it exists.
7.1.3. CUU: ESC[#A Cursor Up
Moves the cursor up the given number of rows without changing its hor-
izontal position.
7.1.4. CUD: ESC[#B Cursor Down
Moves the cursor down the given number of rows without changing its
horizontal position.
7.1.5. CUF: ESC[#C Cursor Forward
Moves the cursor right the given number of columns without changing
its vertical position.
7.1.6. CUB: ESC[#D Cursor Backward
Moves the cursor left the given number of columns without changing its
vertical position.
7.1.7. DSR: ESC[#n Device Status, Report!
# must be 6. The sequence ESC[6n causes the console driver to output
a CPR (Cursor Position Report) sequence.
Note: This sequence is not supported by the ANSI.SYS emulator built
into Microsoft Windows 1.x or 2.x.
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7.1.8. CPR: ESC[#;#R Cursor Position Report
The console driver outputs this sequence upon reciept of a DSR
sequence. The first parameter is the cursor's vertical position; the
second parameter is the cursor's horizontal position.
Note: Contrary to the MS-DOS manual, ANSI.SYS outputs a carriage
return after this sequence. NANSI.SYS faithfully reproduces this
quirk.
The resulting string can have up to eleven characters. For example,
if you have a 100-line display (wow), and the cursor is at
(x=132,y=100), the string will be ESC[132;100R followed by a carriage
return.
This should never be sent to the console driver.
Also note: This sequence is not supported by the ANSI.SYS emulator
built into Microsoft Windows 1.x or 2.x.
Here is an example of how to use DSR/CPR to find the current cursor
position with the C language:
/* Code fragment to get current cursor X and Y from console */
/* Be sure to disable line-buffering on stdin before calling */
int x, y, c;
printf("\033[6n");
fflush(stdout);
if (getchar() != '\033' || getchar() != '[')
abort("Console not responding to DSR?");
for (y=0; isdigit(c=getchar()); y=y*10+(c-'0'));
if (c != ';')
abort("Console CPR faulty?");
for (x=0; isdigit(c=getchar()); x=x*10+(c-'0'));
if (c != 'R')
abort("Console CPR faulty?");
#ifndef VT100
getchar(); /* ignore trailing CR */
#endif
This can also be useful for sensing screen size.
7.1.9. SCP: ESC[s Save Cursor Position
Saves the cursor's X and Y locations in an internal variable. See
RCP.
7.1.10. RCP: ESC[u Restore Cursor Position
Moves cursor to the position it held when the last SCP sequence was
received.
November 29, 1991
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7.2. Sequences that Edit the Display
7.2.1. ED: ESC[#J Erase in Display
# must be 2. Clears the entire screen.
Note: Contrary to the MS-DOS manual, ANSI.SYS also moves the cursor to
the upper left corner of the screen. Contrary to the ANSI standard,
ANSI.SYS does not insist on # being 2. NANSI.SYS faithfully repro-
duces these quirks. (Version 2.2 of NANSI.SYS insisted on # being 2,
and it caused compatibility problems with programs that ignored the
MS-DOS manual. Sigh.)
7.2.2. EL: ESC[K Erase in Line
Deletes from the cursor to the end of the line.
7.2.3. IL: ESC[#L Insert Lines
The cursor line and all lines below it move down # lines, leaving
blank space. The cursor position is unchanged. The bottommost #
lines are lost.
Note: This is not supported in ANSI.SYS.
7.2.4. DL: ESC[#M Delete Lines
The block of # lines at and below the cursor are deleted; all lines
below them move up # lines to fill in the gap, leaving # blank lines
at the bottom of the screen. The cursor position is unchanged.
Note: This is not supported in ANSI.SYS.
7.2.5. ICH: ESC[#@ Insert Characters
The cursor character and all characters to the right of it move right
# columns, leaving behind blank space. The cursor position is
unchanged. The rightmost # characters on the line are lost.
Note: This is not supported in ANSI.SYS.
7.2.6. DCH: ESC[#P Delete Characters
The block of # characters at and to the right of the cursor are
deleted; all characters to the right of it move left # columns, leav-
ing behind blank space. The cursor position is unchanged.
Note: This is not supported in ANSI.SYS.
November 29, 1991
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7.3. Sequences that Set Modes
7.3.1. KKR: ESC["string"p Keyboard Key Reassignment
The first char (or, for function keys, two chars) of the string gives
the key to redefine; the rest of the string is the key's new value.
To specify unprintable chars, give the ASCII value of the char outside
of quotes, as a normal parameter. IBM function keys are two byte
strings starting with zero. For instance, ESC[0;59;"dir a:";13p rede-
fines function key 1 to have the value "dir a:" followed by the ENTER
key.
There are about 500 bytes available to hold redefinition strings.
Once this space fills up, new strings are ignored.
To clear all definitions, send the string ESC[p. (There was no way to
do this in ANSI.SYS.)
This feature is a security risk, and can be disabled with the /s
option when loading Nansi in config.sys. See Command-line Options
above.
Here's a table of the ASCII values of the common function keys; for
others, see the IBM Basic manual or the "IBM PS/2 and PC BIOS Inter-
face Technical Reference," a steal at $80 from IBM (1-800-IBM-PCTB).
F1 0;59 F2 0;60 F3 0;61 F4 0;62
F5 0;63 F6 0;64 F7 0;65 F8 0;66
F9 0;67 F10 0;68 F11 0;133 F12 0;134
HOME 0;71 END 0;79 PGUP 0;73 PGDN 0;81
INS 0;82 DEL 0;83 LEFT 0;75 RIGHT 0;77
UP 0;72 DOWN 0;80
When /X is given, the gray Insert, Delete, Home, End, PageUp, PageDn,
and arrow keys on an Extended keyboard can be redefined separately by
using 224 rather than 0 as the initial byte.
7.3.2. SGR: ESC[#;#;...#m Set Graphics Rendition
The Set Graphics Rendition command is used to select foreground and
background colors or attributes. When you use multiple parameters,
they are executed in sequence, and the effects are cumulative.
Attrib Value
0 All attributes off (normal white on black)
1 Bold
4 Underline
5 Blink
7 Reverse Video
30-37 foreground black/red/green/yellow/blue/magenta/cyan/white
40-47 background black/red/green/yellow/blue/magenta/cyan/white
November 29, 1991
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7.3.3. SM: ESC[=nh Set Video Mode
This sequence selects one of the available video modes. The IBM BIOS
supports several video modes; the codes given in the BIOS documenta-
tion are used as parameters to the Set Mode command. (In bitmap
modes, the cursor is simulated with a small blob (^V).)
Mode Code Value
0 text 40x25 Black & White
1 text 40x25 Color
2 text 80x25 Black & White
3 text 80x25 Color
4 bitmap 320x200 4 bits/pixel
5 bitmap 320x200 1 bit/pixel
6 bitmap 640x200 1 bit/pixel
13 bitmap 320x200 4 bits/pixel
14 bitmap 640x200 4 bits/pixel
15 bitmap 640x350 1 bit/pixel
16 bitmap 640x350 4 bits/pixel
17 bitmap 640x480 1 bit/pixel
18 bitmap 640x480 4 bits/pixel
19 bitmap 320x200 8 bits/pixel
Modes 0, 1, and 4-19 require a CGA, EGA or VGA.
Modes 13-16 require an EGA or VGA.
Modes 17-19 require a VGA.
Other graphics cards may support other video modes.
The EGA and VGA let you use a shorter character cell in text modes in
order to squeeze more lines of text out of the 25-line text modes. To
enter short line mode, set the desired 25-line text mode (0 to 3),
then Set Mode 43. For instance: ESC[=3h ESC[=43h. To exit short line
mode, set the desired 25-line text mode again. On IBM VGA cards, this
sequence gives you a 50 line screen. NANSI.SYS ignores mode 43 unless
there is an EGA or VGA on your computer.
November 29, 1991
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7.3.4. SM: ESC[?nh Set Nonvideo Mode
This sequence is used to set non-video modes. The only value sup-
ported is
Mode Code Value when set
7 Cursor wraps at end of line
Setting mode 7 tells the cursor to wrap around to the next line when
it passes the end of a line.
7.3.5. RM: ESC[?nl Reset Nonvideo Mode
This sequence is used to reset non-video modes. The only value sup-
ported is
Mode Code Value when reset
7 Cursor stops at end of line
Resetting mode 7 tells the cursor to 'stick' at the end of the line
instead of wrapping to the next line.
November 29, 1991
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8. Background - What does a console driver do, and how?
A console driver consists of subroutines which are called by MS-DOS.
MS-DOS itself is mostly just subroutines which can be called by appli-
cation programs.
Programs that want to display text on the screen can call the "Write"
subroutine provided by MS-DOS. This subroutine in turn calls the
"Write" subroutine of the console driver.
When you, for example, type
C> type foo.txt
COMMAND.COM uses the "Read" subroutine of MS-DOS to read the file
"foo.txt" from the disk; it then uses the "Write" subroutine of MS-DOS
with the file's contents. MS-DOS then calls the console driver's
"Write" subroutine, which finally puts the data up on the screen.
Both ANSI.SYS and NANSI.SYS use IBM Video BIOS to control the screen.
However, NANSI.SYS writes directly to the screen in text modes; this
allows much faster operation.
9. How to Display Text Quickly
Output to the screen via DOS is usually slow because characters are
sent one-at-a-time through several layers of software. Application
programs often call a DOS function for each character or line.
To avoid this overhead, application programs should write as many
characters per DOS call as possible (in C programs, this means using
setbuf(), fflush(), and buffered output).
Another problem is that application programs sometimes send line after
line of text, letting the cursor stay at the bottom of the screen.
This forces the console driver to scroll the entire screen up once for
each line displayed, which is rather expensive.
This can be fixed by having the application program clear the screen
and home the cursor after each page of output.
Finally, the biggest problem is that DOS calls the device driver once
or twice for each character written.
Fortunately, DOS can be told to pass the entire write request directly
to the device driver; this is called "raw" mode. The files RAW.C and
RAW.H, included in this package, provide an easy way to set and clear
"raw" mode, to turn break checking on and off, and to check for keys-
trokes when in raw mode.
Even if you follow all these rules, output with ANSI.SYS will still be
very slow, simply because IBM did a bad job designing BIOS, and
because ANSI.SYS was written with total disregard for performance.
NANSI.SYS, on the other hand, was written by a performance fanatic.
November 29, 1991
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10. NANSI and Microsoft Windows
Microsoft Windows 1.x and 2.x allowed you to run command.com in a win-
dow, but did not give you access to NANSI.SYS. Windows 3.0 gives you
full access to NANSI.SYS, even when running command.com in a window
(wow!). However, you can only do this if you have a 386-based com-
puter (boo, hiss); on other computers, Windows runs command.com only
in full screen mode.
Under Microsoft Windows 3.0, if you write text to stdout in RAW mode,
the display is not refreshed until the end of the write; no intermedi-
ate scrolling is shown. I suspect this is because Windows doesn't
refresh the display until display memory hasn't been touched for a few
milliseconds.
11. New in version 3.3 of NANSI.SYS
Fixed bug that caused erratic behavior after ESC[p. Bug was present
in all prior versions of NANSI.
Fixed a few typos in documentation.
12. New in version 3.2 of NANSI.SYS
Can finally read F11 and F12!
New /K command-line option forces Nansi to use Extended Keyboard BIOS
calls if for some reason Nansi doesn't recognize the extended key-
board.
New /X command-line option lets user redefine "new" cursor motion keys
independently of "old" cursor motion keys.
Both of these switches are compatible with the switches of the same
name in ANSI.SYS.
13. New in version 3.1 of NANSI.SYS
A new escape sequence has been added to enable and disable the simu-
lated cursor in graphics mode (see SET MODE 99). The graphics cursor
is disabled by default.
Nansi can now sense options given on the DEVICE=NANSI.SYS line in
config.sys.
/S command-line option has been added to disable the keyboard redefin-
ition escape sequence. This closes up a big security loophole.
/T command-line option has been added to allow the user to tell Nansi
about nonstandard text video modes (see COMMAND-LINE OPTIONS). This
is important if you want to use non-IBM text modes properly, as Nansi
treats nonstandard modes as graphics by default, which results in
slower display.
November 29, 1991
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14. New in version 3.0 of NANSI.SYS
Now obeys BIOS's idea of number of screen lines, when supported.
Works properly when on video pages greater than zero, too.
Supports 132-column displays.
Deleted Output Character Translation feature. It took up 260 bytes,
and nobody ever used it.
Fixed bug related to setting background color while in graphics mode.
No longer assumes AH is zero upon entry to driver.
November 29, 1991
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15. Limitations in the current version of NANSI.SYS
Video modes are specified in hexadecimal on the command line, and in
decimal in escape sequences. This is a needless inconsistancy, but
since users' manuals usually specify the mode numbers in hex, it
shouldn't be too big a bother. You can convert a hexadecimal number
to decimal in BASIC with the print command. For example, from the DOS
prompt, typing
C:>basic
print &h7f
system
displays "127".
All parameter values must be between 0 and 255.
The maximum number of characters available for keyboard redefinition
is 500. Any single keyboard redefinition escape sequence must be
shorter than (500 - (total keyboard redefinition space already used))
bytes.
Insert and delete character do not work in graphics modes.
Graphics mode writing is slow. If this bothers you, try NNANSI, which
is someone else's modification of NANSI v2.2 to attack just this prob-
lem.
Does not support erase-to-end-of-screen and other useful functions.
Nansi determines whether the BIOS number-of-screen-lines variable is
supported by checking for an EGA card. There might be a better way.
Nansi only checks for an EGA or VGA card at startup time. If you have
two video cards installed, and one shows more text lines per screen
than the other, AND you switch between the cards without rebooting,
Nansi could conceivably become confused about the number of text lines
on the screen.
November 29, 1991
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