ANSI.SYS
Template:Short description ANSI.SYS is a device driver in the DOS family of operating systems that provides extra console functions through ANSI escape sequences. It is partially based upon a subset of the text terminal control standard proposed by the ANSI 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 as Template:Mono,<ref name="ANSI.COM" /> Template:Mono<ref name="NANSI.SYS" /> and Template:Mono<ref name="Sweger_2007_ANSIPLUS" /> to attempt to change this.Template:Third-party inline
Usage
To use Template:Mono under DOS, a line is added to the Template:Mono (or Template:Mono under Windows NT based versions of Windows) file that reads:
- DEVICE=drive:\path\ANSI.SYS options
where drive: and path are the drive letter and path to the directory in which the file Template:Mono is found, and options can be a number of optional switches to control the behaviour. Template:Mono may also be loaded into upper memory via Template:Mono/Template:Mono.
- Template:Mono use extended keyboard BIOS functions (INT 16h) rather than standard ones<ref name="RHS_2007" /> This made the F11 and F12 keys work.
- Template:Mono force number of lines
- Template:Mono adjust line scrolling to support screen readers<ref name="RHS_2007" />
- Template:Mono or Template:Mono set screensize
- Template:Mono support redefinition of extended key codes independent of standard codes<ref name="RHS_2007" />
Functionality
Using this driver, programs that write to the standard output can write escape sequences to make use of the 16 text foreground colors and 8 background colors available in VGA-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 80×25 text 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 standard Template:Mono is very slow as it maps escape sequences to BIOS calls (which managed to be designed so that two calls were needed to put a character on the screen and move the cursor right). Several companies made third-party replacements such as Template:Mono<ref name="NANSI.SYS" /> that interface directly with the video memory, in a similar way to most DOS programs that have a full-screen user interface.
Template:Tt checked if this driver was in use, and changed the Template:Mono command to use an escape sequence instead of a BIOS call.<ref name="Paul_1997_NWDOSTIP" />
Keyboard remapping
An interesting (mis)feature of Template:Mono is the ability to remap any key on the keyboard 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.<ref name="uVGA_2012_keycodes" /> This was used to create simple trojans out of text files laced with nefarious keyboard remaps, known as "ANSI bombs". A number of products were released to protect users against this:
- Many replacements for Template:Mono support a command line switch to disable the key remapping feature, f.e. the option Template:Mono (Secure) in Datalight ROM-DOS<ref name="Datalight_2005_ROM-DOS" /> or NANSI.SYS<ref name="NANSI.SYS" /> of FreeDOS. Other ANSI drivers like ANSIPLUS can be configured to disable the redefinition of keys as well.<ref name="Sweger_2007_ANSIPLUS" />
- Some replacements were deliberately designed never to support the keyboard remapping functions.<ref name="Paragon_2000_PTS-DOS" /><ref name="Ellsässer_2004_PTSDOS" />
- PKWARE produced a terminate-and-stay-resident program, PKSFANSI (PK Safe ANSI), which filters out keyboard remapping escape codes as they are written to the standard output.<ref name="PK" /> This has the advantage that the user can load some useful remappings from a text file and then run PKSFANSI to prevent further, possibly malicious remappings.
Occurrence
Template:Mono appeared in MS-DOS 2.0, the first version of the operating system supporting device drivers.<ref name="field198311" /> 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 and DR-DOS.<ref name="Caldera_1998_DRDOS702" />
Template:Mono was required to run some software that used its cursor and color control functions.<ref name="Caldera_1998_DRDOS702" /> It could also be used to enable elaborate color codes in the Template:Mono prompt. These uses were overshadowed by the use of Template:Mono in BBSes; ANSI escape sequences were used to enable BBSes to send text graphics more elaborate than ASCII art, and to control the cursor in ways that were used in a number of online games and similar features.
Most versions of Windows did not support ANSI escape codes in any useful way (it could be used by MSDOS emulation in some versions). In Windows 10 support for similar escape sequences was built into the Win32 console (the text terminal window), but must be activated using the Windows API function <syntaxhighlight lang="text" class="" style="" inline="1">SetConsoleMode</syntaxhighlight> by setting the <syntaxhighlight lang="text" class="" style="" inline="1">ENABLE_VIRTUAL_TERMINAL_PROCESSING</syntaxhighlight> flag.<ref>Template:Cite web</ref>
Features
CSI (Control Sequence Introducer) is a placeholder for the common two-byte escape lead-in sequence "Template:Mono" (that is, Template:Mono).<ref name="Caldera_1998_DRDOS702" /> The ANSI standard also defines an alternative single-byte CSI code Template:Mono, which is not supported by ANSI.SYS (this code instead drew a cent sign Template:Angbr from CP437).
Standard DOS Template:Mono drivers support only the following sub-set of ANSI escape sequences:<ref name="Caldera_1998_DRDOS702" />
| 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)<ref group="nb" name="NB_MSDOS_ANSI_J" /> |
| ESC [ n K | Erase in line (EL) (n=0 or n=0, 1, 2)<ref group="nb" name="NB_MSDOS_ANSI_J" /> |
| 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 of Template:Mono. 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<ref group="nb" name="NB_ANSI_J" /> |
Set screen mode (SM)<ref group="nb" name="NB_ANSI_J" /> |
| ESC [ n l ESC [ ?n l ESC [ =n l ESC [ >n l<ref group="nb" name="NB_ANSI_J" /> |
Reset screen mode (RM)<ref group="nb" name="NB_ANSI_J" /> |
| ESC [ n q | Enable (n=1) or disable (n=0) Template:Mono support<ref group="nb" name="NB_MSDOS_X" /> |
| ESC [ L | Insert line (IL)<ref group="nb" name="NB_MSDOS_J" /> |
| ESC [ M | Delete line (DL)<ref group="nb" name="NB_MSDOS_J" /> |
| ESC $ ) 1 | Switch keyboard input mode to Korean (Hangul)<ref group="nb" name="NB_ANSI_KOREAN" /> |
| ESC ( 2 | Switch keyboard input mode to English<ref group="nb" name="NB_ANSI_KOREAN" /> |
| ESC [ + | Enable console output<ref group="nb" name="NB_DRDOS_ANSI_X" /> |
| ESC [ - | Disable console output<ref group="nb" name="NB_DRDOS_ANSI_X" /> |
| 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<ref group="nb" name="NB_SM-RM" /> | ||
| 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)<ref group="nb" name="NB_DRDOS_ANSI_J" /> | 115 | 640 x 475 color (16-color graphics)<ref group="nb" name="NB_DRDOS_ANSI_J" /> |
In some DOS implementations, video modes above 7 are not documented. Under Multiuser DOS, the only valid argument in conjunction with PCTERM is 7.