ANSI.SYS is adevice driver in theDOS family ofoperating systems that provides extraconsole functions throughANSI escape sequences. It is partially based upon a subset of thetext terminal control standard proposed by theANSI X3L2 Technical Committee on Codes and Character Sets (the "X3 Committee").
As it was not installed by default, and was notoriously slow, little software took advantage of it and instead resorted to directly manipulating the IBM PC hardware. A number of third-party alternatives that ran at reasonable speed were created, such asANSI.COM,[1]NANSI.SYS[2] andANSIPLUS.EXE[3] to attempt to change this.[independent source needed]
To useANSI.SYS under DOS, a line is added to theCONFIG.SYS (orCONFIG.NT underWindows NT based versions ofWindows) file that reads:
wheredrive: andpath are thedrive letter and path to thedirectory in which the fileANSI.SYS is found, andoptions can be a number of optional switches to control the behaviour.ANSI.SYS may also be loaded intoupper memory viaDEVICEHIGH/HIDEVICE.
Using this driver, programs that write to thestandard output can write escape sequences to make use of the 16 text foreground colors and 8 background colors available inVGA-compatible text mode, make text blink, change the location of the cursor on the screen, and blank the screen. They could also change the video mode from standard 80×25text mode to a number of different graphics modes (for example, 320×200 graphics mode with text drawn as pixels, though ANSI.SYS is not able to turn individual pixels on and off).
The standardANSI.SYS is very slow as it maps escape sequences toBIOS calls (which managed to be designed so thattwo calls were needed to put a character on the screen and move the cursor right). Several companies made third-party replacements such asNANSI.SYS[2] that interface directly with thevideo memory, in a similar way to most DOS programs that have a full-screen user interface.
COMMAND.COM checked if this driver was in use, and changed theCLS command to use an escape sequence instead of a BIOS call.[5]
An interesting (mis)feature ofANSI.SYS is the ability to remap any key on thekeyboard in order to perform shortcuts or macros for complex instructions. Using special escape sequences, the user can define any keystroke that has a character-code mapping to simulate an arbitrary sequence of such keystrokes.[6] This was used to create simpletrojans out of text files laced with nefarious keyboard remaps, known as "ANSI bombs". A number of products were released to protect users against this:
ANSI.SYS appeared inMS-DOS 2.0, the first version of the operating system supporting device drivers.[11] It was supported by all following versions of MS-DOS. It is also present in many non-Microsoft DOS systems, e.g.IBM PC DOS andDR-DOS.[12]
ANSI.SYS was required to run some software that used its cursor and color control functions.[12] It could also be used to enable elaborate color codes in theCOMMAND.COM prompt. These uses were overshadowed by the use ofANSI.SYS inBBSes; ANSI escape sequences were used to enable BBSes to sendtext graphics more elaborate thanASCII art, and to control the cursor in ways that were used in a number ofonline games and similar features.
Most versions of Windows did not supportANSI escape codes in any useful way (it could be used by MSDOS emulation in some versions). InWindows 10 support for similar escape sequences was built into theWin32 console (the text terminal window), but must be activated using theWindows API functionSetConsoleMode by setting theENABLE_VIRTUAL_TERMINAL_PROCESSING flag.[13]
CSI (Control Sequence Introducer) is a placeholder for the common two-byte escape lead-in sequence "ESC [" (that is,0x1B 0x5B).[12] The ANSI standard also defines an alternative single-byte CSI code0x9B, which is not supported by ANSI.SYS (this code instead drew a cent sign⟨¢⟩ fromCP437).
Standard DOSANSI.SYS drivers support only the following sub-set of ANSI escape sequences:[12]
| Sequence | Effect |
|---|---|
| ESC [r A | Cursor up (CUU) |
| ESC [r B | Cursor down (CUD) |
| ESC [c C | Cursor forward (CUF) |
| ESC [c D | Cursor back (CUB) |
| ESC [r;c f | Horizontal and vertical position (HVP) |
| ESC [r;c H | Cursor position (CUP) |
| ESC [n J | Erase display (ED) (n=0, 2 or n=0, 1, 2)[nb 1] |
| ESC [n K | Erase in line (EL) (n=0 or n=0, 1, 2)[nb 1] |
| ESC [n m | Select graphic rendition (SGR) (n=0..47) |
| ESC [ 6 n | Device status report (DSR) requests cursor position, returned as cursor position report (CPR): ESC [r;c R |
| ESC [ s | Save cursor position (SCP) |
| ESC [ u | Restore cursor position (RCP) |
There are also some escape sequences specific to the implementation ofANSI.SYS. They are not generally supported by ANSI consoles in other operating systems.
| Sequence | Effect |
|---|---|
| ESC [n h ESC [ ?n h ESC [ =n h ESC [ >n h[nb 2] | Setscreen mode (SM)[nb 2] |
| ESC [n l ESC [ ?n l ESC [ =n l ESC [ >n l[nb 2] | Reset screen mode (RM)[nb 2] |
| ESC [n q | Enable (n=1) or disable (n=0)/X support[nb 3] |
| ESC [ L | Insert line (IL)[nb 4] |
| ESC [ M | Delete line (DL)[nb 4] |
| ESC $ ) 1 | Switch keyboard input mode to Korean (Hangul)[nb 5] |
| ESC ( 2 | Switch keyboard input mode to English[nb 5] |
| ESC [ + | Enable console output[nb 6] |
| ESC [ - | Disable console output[nb 6] |
| ESC [a;b;... p | Set key re-definement (SKR/KR) |
| Mode | Description | Mode | Description |
|---|---|---|---|
| 0 | 40 × 25 monochrome | 1 | 40 × 25 color |
| 2 | 80 × 25 monochrome | 3 | 80 × 25 color |
| 4 | 320 × 200 color | 5 | 320 × 200 monochrome |
| 6 | 640 × 200 monochrome | ||
| 7 | Wrap at end of line[nb 7] | ||
| 13 | 320 x 200 color (graphics) | 14 | 640 x 200 color (16-color graphics) |
| 15 | 640 x 350 monochrome (2-color graphics) | 16 | 640 x 350 color (16-color graphics) |
| 17 | 640 x 480 monochrome (2-color graphics) | 18 | 640 x 480 color (16-color graphics) |
| 19 | 320 x 200 color (256-color graphics) | ||
| 114 | 640 x 480 color (16-color graphics)[nb 8] | 115 | 640 x 475 color (16-color graphics)[nb 8] |
In some DOS implementations, video modes above 7 are not documented. UnderMultiuser DOS, the only valid argument in conjunction withPCTERM is 7.
{{cite book}}:|work= ignored (help) (NB. NWDOSTIP.TXT is a comprehensive work on Novell DOS 7 and OpenDOS 7.01, including the description of many undocumented features and internals. It is part of the author's yet largerMPDOSTIP.ZIP collection maintained up to 2001 and distributed on many sites at the time. The provided link points to a HTML-converted older version of theNWDOSTIP.TXT file.)[1]