CTerm Manual

The cursor is moved to the first character of the next line as soon as a character is written to the last column of the current line, not on the next character. A tab will wrap to the next line only if the current cursor position is the last character on the line. This behavior is often surprising to people who are used to VT emulators which implement the LCF as documented in [STD-070], who expect the cursor to "stick" in the last column until the next character is received.

There are two settable flags that will impact the default behaviour.

CSI ? 7 l will disable wrapping at the end of line completely, and any characters written to the last column will not move the cursor at all, overwriting the existing charater. Default behaviour can be restored with CSI ? 7 h.

If the CSI = 4 h sequence is received, CTerm will enable LCF mode as documented in [STD-070], and CSI = 4 l will restore default behaviour. CSI = 5 h will set LCF mode and disable CSI = 4 l, as well as cause LCF to remain enabled across an ESC c (RIS).

Specifically, the LCF will be set when displaying a printable character advances the cursor to the right margin, and cleared by any of the following being received: CSI ? 6 h, CSI ? 6 l, CSI ? 7 l, CSI @, CSI A, CSI B, CSI a CSI j, CSI H, CSI f, CSI I, CSI Y, CSI J, CSI K, CSI P CSI X, CSI r, ESC E, ESC M, CR, LF, BS, TAB Any normal printable character when the cursor is at the right margin (of the screen or scrollable area).

In doorway mode, indicates that the next character is a literal character. The IBM CP437 character will be displayed. This allows ESC and other control characters to be placed on the screen.

SOURCE: [BANSI]

Beep

Non-destructive backspace. Moves cursor position to the previous column unless the current column is the first, in which case no operation is performed.

SOURCE: [ECMA-48]

Moves to the next character tabulation stop. Does not overwrite any characters in between. If there are no character tabulation stops left in the line, moves to the first position of the next line. If the starting position is on the last line, will perform a scroll, filling the new line at bottom with the current attribute.

SOURCE: [ECMA-48]

Move cursor position to same column of the next row. If current row is the last row, scrolls the screen up and fills the new row with the current attribute.

SOURCE: [ECMA-48]

Move cursor position to column 1 of the current line

SOURCE: [ECMA-48]

Introduces a control code. The ESC and the next byte together form the control code. If the control code is not valid, the ESC is ignored.

SOURCE: [ECMA-48]

Reserved for use within STS transmitted content (FETM=INSERT mode). OSC 8 hyperlink sequences inside an SOS-framed STS response cannot use bare ST (ESC \) as their terminator because it would prematurely close the SOS frame. Instead, ESC : \ (0x1B 0x3A 0x5C) is used as a substitute terminator.

ESC : is an unassigned Fp private-use escape sequence (per [ECMA-35]). A conformant parser that encounters ESC : outside of STS content silently drops it (per the rule above). Within STS FETM=INSERT content, the host parser recognizes the three-byte sequence ESC : \ as "escaped ST" and converts it to ESC \ before replay.

Saves the current cursor position same as CSI s

SOURCE: [VT102]

Restores the current cursor position same as CSI u

SOURCE: [VT102]

Moves to the line home position of the next line. (Same as CR LF)

SOURCE: [ECMA-48]

Marks the active presentation position as the first character position of a selected area. The content from SSA to ESA (or to the cursor position, depending on TTM) is eligible for transmission when STS is received.

SSA and ESA are cleared by changes to scroll margins (DECSTBM, DECSLRM), origin mode (DECOM), or RIS.

Scrolling does not invalidate SSA — it marks a position in the presentation component, not the content at that position. When STS triggers, the terminal reads whatever content is currently at the marked positions.

SOURCE: [ECMA-48] (Section 8.3.138)

Marks the active presentation position as the last character position (inclusive) of a selected area begun by SSA.

ESA is required when TTM is set to ALL (CSI 16 h). When TTM is CURSOR (the default), the cursor position defines the end instead.

If no ESA has been issued, the selected area extends to the last cell of the viewport.

SOURCE: [ECMA-48] (Section 8.3.47)

Sets a character tabulation stop at the current column.

SOURCE: [ECMA-48]

Sets a line tabulation stop at the current line. Line tabulation stops are used by CVT (CSI Pn Y) and can be cleared by TBC with parameter values 1, 4, or 5.

Line tabulation stops are at fixed row numbers and are not affected by scrolling. No default line tabulation stops are set.

SOURCE: [ECMA-48]

Move up one line

SOURCE: [ECMA-48]

Begins a string consisting of the characters 0x08 - 0x0d and 0x20-0x7e, terminated by a String Terminator (ST)

If a byte outside the valid range (other than ESC) is received, the string is discarded and the byte is re-processed as normal input. This applies to all command strings: DCS, OSC, PM, and APC.

Introduces Device Control Strings

SOURCE: [ECMA-48]

Triggers transmission of the selected area content established by SSA (and optionally ESA) back to the host.

The response is framed as SOS CTerm:STS:<N>: <content> ST where <N> is 0 for FETM=INSERT (attributed) or 1 for FETM=EXCLUDE (text only).

With TTM=CURSOR (default, CSI 16 l): Content from SSA up to but excluding the cursor position is transmitted.

With TTM=ALL (CSI 16 h): Content from SSA through ESA (inclusive) is transmitted regardless of cursor position.

With FETM=INSERT (default, CSI 14 l): Characters are transmitted with SGR sequences for attribute changes, doorway mode encoding for C0 control characters in cells, and OSC 8 for hyperlink changes. The stream is valid ECMA-48 that can be replayed to reproduce the region (after escaped-ST expansion; see below).

Escaped ST in attributed content: OSC 8 sequences require ST (ESC \) as their terminator, but bare ST would prematurely close the SOS frame. Within STS FETM=INSERT content, OSC 8 sequences are terminated with ESC : \ (0x1B 0x3A 0x5C) instead of ESC \ (0x1B 0x5C). ESC : is an unassigned Fp private-use escape sequence (per ECMA-35) that any conformant parser silently drops. The host parser recognizes ESC : \ within STS content as "escaped ST" and converts it to ESC \ before replay.

With FETM=EXCLUDE (CSI 14 h): Only graphic characters are transmitted. C0 and DEL bytes in cells are replaced with SPACE.

The transmitted stream is a linear sequence of character positions in presentation order (left to right, top to bottom). No line boundary markers are emitted — the host slices by the known screen width.

If no SSA has been issued, or the eligible area is empty, an empty response is returned: SOS CTerm:STS:<N>: ST

STS automatically clears the transmit state after transmission completes.

SOURCE: [ECMA-48] (Section 8.3.145)

As the above strings, but may contain any characters except a Start Of String sequence or a String Terminator sequence.

SOURCE: [ECMA-48]

Introduces Control Sequences

Ends a string.

SOURCE: [ECMA-48]

Begins a string consisting of the characters 0x08 - 0x0d and 0x20-0x7e, terminated by a String Terminator (ST)

Introduces Operating System Commands

SOURCE: [ECMA-48]

Begins a string consisting of the characters 0x08 - 0x0d and 0x20-0x7e, terminated by a String Terminator (ST) The string is currently ignored.

SOURCE: [ECMA-48]

Begins a string consisting of the characters 0x08 - 0x0d and 0x20-0x7e, terminated by a String Terminator (ST)

Introduces Application Program Commands

SOURCE: [ECMA-48]

Resets all the terminal settings, clears the screen, and homes the cursor.

SOURCE: [ECMA-48]

Parameters are expressed by the {'0' (ZERO) to '?'} character set.

Sequences which use parameters use decimal parameters separated by a ';'. The use of a ':' from the set is reserved.

If the parameter string begins with '<', '=', '>', or '?' then this is a non-standard extension to the ANSI spec.

If a default is defined, the parameter is optional

Defaults: Pn = 1
Moves text from the current position to the right edge Pn characters to the right, with rightmost characters going off-screen and the resulting hole being filled with the current attribute.

SOURCE: [ECMA-48]

Defaults: Pn = 1
Shifts the contents of the screen left Pn columns(s) with leftmost columns going off-screen and the resulting hole being filled with the current attribute.

SOURCE: [ECMA-48]

Defaults: Pn = 1
Moves the cursor position up Pn lines from the current position. Attempting to move past the screen boundaries stops the cursor at the screen boundary.

SOURCE: [ECMA-48]

Defaults: Pn = 1
Shifts the contents of the screen right Pn columns(s) with rightmost columns going off-screen and the resulting hole being filled with the current attribute.

SOURCE: [ECMA-48]

Defaults: Pn = 1
Moves the cursor position down Pn lines from the current position. Attempting to move past the screen boundaries stops the cursor at the screen boundary.

SOURCE: [ECMA-48]

Defaults: Pn = 1 Moves the cursor position right Pn columns from the current position. Attempting to move past the screen boundaries stops the cursor at the screen boundary.

SOURCE: [ECMA-48]

Defaults: Pn = 1 Moves the cursor position left Pn columns from the current position. Attempting to move past the screen boundaries stops the cursor at the screen boundary.

SOURCE: [ECMA-48]

Defaults: Ps1 = 0 Ps2 = 0 "sp" indicates a single space character. Sets font Ps1 to be the one indicated by Ps2. Currently four fonts are supported. Ps2 must be between 0 and 255. Not all output types support font selection. Only X11 and SDL currently do.

Not all fonts are supported in all modes. If a font is not supported in the current mode, no action is taken, but there should be a non-zero 'Font Selection result' value in the Font State Report.

SOURCE: [ECMA-48]

Defaults: Pn = 1
Moves the cursor to the first column of the line Pn down from the current position. Attempting to move past the screen boundaries stops the cursor at the screen boundary.

SOURCE: [ECMA-48]

Defaults: Pn = 1
Moves the cursor to the first column of the row Pn up from the current position. Attempting to move past the screen boundaries stops the cursor at the screen boundary.

SOURCE: [ECMA-48]

Defaults: Pn = 1
Movies the cursor to column Pn of the current row.

SOURCE: [ECMA-48]

Defaults: Pn1 = 1 Pn2 = 1
Moves the cursor to the `Pn2`th column of the `Pn1`th line.

SOURCE: [ECMA-48]

Defaults: Pn = 1
Move the cursor to the Pn-th next tab stop. Basically the same as sending TAB Pn times.

SOURCE: [ECMA-48]

Defaults: Ps = 0
Erases from the current screen according to the value of Ps

Erased characters are set to the current attribute.

SOURCE: [ECMA-48], [BANSI]

Defaults: Ps = 0
Erases from the current line according to the value pf Ps

Erased characters are set to the current attribute.

SOURCE: [ECMA-48]

Defaults: Pn = 1
Inserts Pn lines at the current line position. The current line and those after it are scrolled down and the new empty lines are filled with the current attribute. If the cursor is not currently inside the scrolling margins, has no effect.

SOURCE: [ECMA-48]

Defaults: Pn = 1 Deletes the current line and the Pn - 1 lines after it scrolling the first non-deleted line up to the current line and filling the newly empty lines at the end of the screen with the current attribute. If the cursor is not currently inside the scrolling margins, has no effect. If "ANSI" Music is fully enabled (CSI = 2 M), and no parameter is specified, performs "ANSI" music instead. See "ANSI" MUSIC section for more details.

SOURCE: [ECMA-48], [BANSI]

NON-STANDARD EXTENSION.
Defaults: Ps = 0
Sets the current state of ANSI music parsing. 0 - Only CSI | will introduce an ANSI music string. 1 - Both CSI | and CSI N will introduce an ANSI music string. 2 - CSI |, CSI N, and CSI M will all introduce an ANSI music string. In this mode, Delete Line will not be available.

"ANSI" Music / Not implemented. If "ANSI" Music is set to BananaCom (CSI = 1 M) or fully enabled (CSI = 2 M) performs "ANSI" music. See "ANSI" MUSIC section for more details.

SOURCE: [BANSI]

Defaults: Pn = 1
Deletes the character at the current position by shifting all characters from the current column + Pn left to the current column. Opened blanks at the end of the line are filled with the current attribute. If the cursor is not currently inside the scrolling margins, has no effect.

SOURCE: [ECMA-48]

Defaults: Pn = 1
Scrolls the screen up Pn lines. New lines emptied at the bottom are filled with the current attribute.

SOURCE: [ECMA-48]

If Ps1 is 2, and Ps2 is 1, replies with the graphics screen information in the following format: CSI ? 2 ; 0 ; Px ; Py S Where Px is the width of the screen in pixels and Py is the height.

SOURCE: [XTerm]

Defaults: Pn = 1
Scrolls all text on the screen down Pn lines. New lines emptied at the top are filled with the current attribute.

SOURCE: [ECMA-48]

Defaults: Pn = 1
Erase p1 characters starting at the current character. Will not erase past the end of line. Erased characters are set to the current attribute. This can erase across scroll margins.

SOURCE: [ECMA-48]

Defaults: Pn = 1
Moves the cursor to the corresponding character position (same column) of the line corresponding to the Pn-th following line tabulation stop. Line tabulation stops are set by VTS (ESC J).

If there is no next line tabulation stop, the screen scrolls up one line and the cursor moves to the last row, preserving the current column.

SOURCE: [ECMA-48]

Defaults: Pn = 1
Move the cursor to the Pnth preceding tab stop. Will not go past the start of the line.

SOURCE: [ECMA-48]

Defaults: Pn = 1
Move the cursor to the specified position on the current row. Will not go past the end of the line.

SOURCE: [ECMA-48]

Defaults: Pn = 1
Moves the cursor position forward Pn columns from the current position. Attempting to move past the screen boundaries stops the cursor at the screen boundary.

SOURCE: [ECMA-48]

Defaults: Pn = 1
Repeats the previous graphic character Pn times. Will not repeat escape sequences.

SOURCE: [ECMA-48]

Defaults: Ps = 0
If Ps is 0, CTerm will reply with the sequence: CSI = 67;84;101;114;109;pN c 67;84;101;114;109 is the ASCII values of the "CTerm" string. pN is the revision ID of CTerm with dots converted to semi-colons (e.g. "1;156"). Use the revision to detect if a specific feature is available. If you are adding features to a forked version of cterm, please do so by adding an extra parameter to the end, not by incrementing any existing one!

SOURCE: [ECMA-48]

Defaults: Ps = 0
If Pn is 0, CTerm will reply with the sequence: CSI < 0 ; Ps…​ c

Defaults: Pn = 1
Moves to row specified by Pn.

SOURCE: [ECMA-48]

Defaults: None
Removes a tab stop at postion Pn.

SOURCE: [ECMA-48]

Defaults: Pn = 1
Moves forward Pn rows.

SOURCE: [ECMA-48]

Defaults: Pn1 = 1 Pn2 = 1
Moves the cursor to the Pn2th column of the Pn1th line.

SOURCE: [ECMA-48]

Defaults: Ps = 0
Clears tabulation stops according to the value of Ps:

SOURCE: [ECMA-48]

Sets one or more ANSI modes. The following modes are supported:

SOURCE: [ECMA-48] (Sections 7.2.6, 7.2.18)

NON-STANDARD EXTENSION
Enable DoorWay Mode

SOURCE: [BANSI]

NON-STANDARD EXTENSION
Enable Last Column Flag mode

NON-STANDARD EXTENSION
Force Last Column Flag mode

NON-STANDARD EXTENSION
Sets one or more mode. The following modes are supported:

Defaults: Pn = 1
Moves the cursor position left Pn columns from the current position. Attempting to move past the screen boundaries stops the cursor at the screen boundary.

SOURCE: [ECMA-48]

Defaults: Pn = 1 Moves the cursor position up Pn lines from the current position. Attempting to move past the screen boundaries stops the cursor at the screen boundary.

SOURCE: [ECMA-48]

Resets ANSI modes. Same parameter values as SM above. Resetting mode 14 restores FETM=INSERT (attributed transmission). Resetting mode 16 restores TTM=CURSOR (cursor-exclusive termination).

SOURCE: [ECMA-48]

NON-STANDARD EXTENSION

SOURCE: [BANSI]

NON-STANDARD EXTENSION
Disable Last Column Flag mode

NON-STANDARD EXTENSION
Resets one or more mode. The following modes are supported:

Defaults: Ps1 = 0
Sets or clears one or more text attributes. Unlimited parameters are supported and are applied in received order. The following are supported:

All others are ignored.

Blink indicates the blink bit. Bold indicates the bold bit. FG indicates the foreground colour. BG indicates the background colour. TF indicates that the Tru Colour foreground is changed. TB indicates that the Tru Colour background is changed.

For palette selection, an additional two parameters are required after that value. They are considered part of the 38/48, not separate values. The first additional parameter must be a 5. The second additional parameter specified the palette index to use. To set the foreground to orange, and the background to a fairly dark grey, you would send: CSI 38 ; 5 ; 214 ; 48 ; 5 ; 238 m

The default palette is the XTerm 256-colour palette. [256colors]

For direct colour selection, an additional four parameters are required after that value. They are considered part of the 38/48, not separate values. The first additional parameter must be a 2. The second, third, and fourth specify the R/G/B values respectively. CTerm handles this with an internal temporary palette, so scrollback may not have the correct colours. The internal palette is large enough for all cells in a 132x60 screen to have unique foreground and background colours though, so the current screen should always be as expected.

SOURCE: [ECMA-48], [XTerm]

Defaults: Ps = 0
A request for a status report. CTerm handles the following three requests:

SOURCE: [ECMA-48] (parameters 5 and 6 only) [BANSI] (parameter 255)

NON-STANDARD EXTENSION
Defaults: Ps = 1
When Ps is 1, CTerm will respond with a Font State Report of the form CSI = 1 ;pF ;pR ;pS0 ;pS1 ;pS2 ;pS3 n pF is the first available loadable-font slot number pR is the result of the previous "Font Selection" request:

pS0 - pS3 contain the font slots numbers of previously successful "Font Selection" requests into the 4 available alternate-font style/attribute values:

When Ps is 2, CTerm will respond with a Mode Report of the form CSI = 2[;pN [;pN] […​]] n Where pN represent zero or more mode values set previously (e.g. via CSI ? pN h). Mode values cleared (disabled via CSI ? pN l) will not be included in the set of values returned in the Mode Report. If no modes are currently set, an empty parameter will be included as the first and only pN.

When Ps is 3, CTerm will respond with a Mode Report of the form CSI = 3 ; pH ; pW n Where pH is the height of a character cell in pixels, and pW is the width of a character cell in pixels.

When Ps is 4, CTerm will respond with a Mode Report of the form CSI = 4 ; pF n Where pF is 1 if LCF mode is enabled, and 0 if it is disabled.

When Ps is 5, CTerm will respond with a Mode Report of the form CSI = 5 ; pF n Where pF is 1 if LCF mode is forced, and 0 if it is not.

When Ps is 6, CTerm will respond with a Mode Report of the form CSI = 6 ; pA n Where pA is 1 if OSC 8 hyperlink support is available, and 0 if it is not.

When Ps is 62 (DECMSR) and there is no Pn, CTerm will respond with a Mode Report of the form CSI 32767 * { This indicates that 524,272 bytes are available for macro storage. This is not actually true, SyncTERM will use all available memory for macro storage, but some software checks this value, and some parsers don’t allow more than INT16_MAX parameter values.

When Ps is 63 (DECCKSR) Pn defaults to 1, and CTerm will respond with a checksum of the defined macros in the form DCS Pn ! xxxx ST Where xxxx is the hex checksum.

SOURCE: [VT420]

Requests the current state of ANSI mode Ps. The terminal responds with CSI Ps ; Pm $ y (DECRPM).

The following ANSI modes can be queried:

All ECMA-48 standard modes are reported. Modes 14 and 16 are changeable; modes 21 and 22 are permanently set; all others are permanently reset. Any unrecognized mode returns Pm=0.

SOURCE: [VT320], [ECMA-48]

NON-STANDARD EXTENSION
Requests the current state of CTerm private mode Ps. The terminal responds with CSI = Ps ; Pm $ y using the same Pm values as DECRQM above.

The following CTerm modes can be queried:

Requests the current state of private mode Ps. The terminal responds with a mode report of the form CSI ? Ps ; Pm $ y (DECRPM) where Pm indicates the mode state:

The following private modes can be queried:

Any unrecognized mode returns Pm = 0.

SOURCE: [VT320]

Defaults: Ps = 1 Sets the cursor style

SOURCE: [VT520]

Defaults: Pn1 = 1 Pn2 = last line on screen
Selects top and bottom margins, defining the scrolling region. Pn1 is the line number of the first line in the scrolling region. Pn2 is the line number of the bottom line.

SOURCE: [VT100]

Defaults: Pt = 1 Pl = 1 Pb = last line Pr = last column
Sets SGR attributes in a rectangular screen area without changing characters. Pt, Pl, Pb, Pr define the rectangle. The remaining Ps parameters are SGR attribute values (same as CSI m), including extended colour sequences (38;5;N, 38;2;R;G;B, 48;5;N, 48;2;R;G;B).

If DECSACE is set to 1 (stream mode), the operation applies as a character stream from (Pt,Pl) to (Pb,Pr) wrapping at line boundaries. In stream mode, Pl > Pr is permitted when Pt < Pb.

Coordinates are affected by DECOM (origin mode). Does not change cursor position.

SOURCE: [VT420]

Set the output emulation speed. If Ps1 or Ps2 are omitted, causes output speed emulation to stop Ps1 may be empty. Sequence is ignored if Ps1 is not empty, 0, or 1. The value of Ps2 sets the output speed emulation as follows:

SOURCE: [VT420]

(Only when DEC Left Right Margin Mode - 69 - is enabled)

Defaults: Pn1 = 1 Pn2 = last column on screen
If either Pn1 or Pn2 is zero, the current setting is retained. Selects left and right margins, defining the scrolling region. Pn1 is the column number of the first column in the scrolling region. Pn2 is the column number of the right column.

SOURCE: [XTerm]

(Only when DEC Left Right Margin Mode - 69 - is disabled) NON-STANDARD EXTENSION Saves the current cursor position for later restoring with CSI u although this is non-standard, it’s so widely used in the BBS world that any terminal program MUST implement it.

SOURCE: [ANSISYS]

NON-STANDARD EXTENSION
Saves the current mode states as specified by CSI ? l and CSI ? h. If Ps1 is omitted, saves all such states. If one or more values of Ps is included, saves only the specified states (arguments to CSI ? l/h).

NON-STANDARD EXTENSION

If Ps is 0, sets the background colour. If Ps is 1, sets the foreground colour. Pn1, Pn2, Pn3 contains the RGB value to set. CTerm handles this with an internal temporary palette, so scrollback may not have the correct colours. The internal palette is large enough for all cells in a 132x60 screen to have unique foreground and background colours though, so the current screen should always be as expected.

Defaults: Pt = 1 Pl = 1 Pb = last line Pr = last column
Toggles (reverses) SGR attributes in a rectangular screen area without changing characters. Pt, Pl, Pb, Pr define the rectangle. The remaining Ps parameters specify which attributes to toggle:

All other Ps values are silently ignored.

If DECSACE is set to 1 (stream mode), the operation applies as a character stream wrapping at line boundaries.

Coordinates are affected by DECOM (origin mode). Does not change cursor position.

SOURCE: [VT420]

Move the cursor to the last position saved by CSI s. If no position has been saved, the cursor is not moved.

SOURCE: [ANSISYS]

NON-STANDARD EXTENSION

Restores the mode states as saved via CSI ? s. If Ps is omitted, restores all such states. If one or more values of Ps is included, restores all the specified states (arguments to CSI ? l/h)

Copies a rectangular area of characters from one location to another. The copied text retains its character values, attributes, and hyperlinks.

Pts, Pls, Pbs, Prs define the source rectangle (top, left, bottom, right). Pps is the source page (ignored — single page). Ptd, Pld define the destination top-left corner. Ppd is the destination page (ignored).

Defaults: Pts = 1, Pls = 1, Pbs = last line, Prs = last column, Ptd = 1, Pld = 1.

If Pbs < Pts or Prs < Pls, DECCRA is ignored. Coordinates are affected by origin mode (DECOM) but not by margins. Values exceeding page dimensions are clamped. The cursor does not move. If the destination area extends past the screen, the off-screen portion is clipped.

SOURCE: [VT420]

Requests a list of tab stops. The list is in the form: DCS 2 $ u Pt ST

The string Pt is a list of tab stops separated by `/`s.

SOURCE: [VT320]

Fills a rectangular area with the character specified by Pch. The fill character uses the visual attributes set by the most recent SGR command. Hyperlinks are cleared on filled cells.

Pch is the decimal value of the fill character. Any value from 0x20 to 0x7E or 0x80 to 0xFF is accepted. If Pch is in the C0 range (0x00–0x1F) or is DEL (0x7F), the command is ignored.

Pt, Pl, Pb, Pr define the rectangle (top, left, bottom, right). Defaults: Pt = 1, Pl = 1, Pb = last line, Pr = last column.

If Pb < Pt or Pr < Pl, DECFRA is ignored. Coordinates are affected by origin mode (DECOM) but not by margins. Values exceeding page dimensions are clamped. The cursor does not move.

SOURCE: [VT420]

Controls whether DECCARA and DECRARA operate on a rectangular area or a character stream.

Reset to 0 by RIS.

SOURCE: [VT420]

Returns a checksum for the specified rectangular area. Pn1 is an ID that is returned in the response. Ps MUST be 1 Pn2 specifies the top row of the rectangle Pn3 specifies the left column of the rectangle Pn4 specifies the bottom row of the rectangle Pn5 specifies the right column of the rectangle The return value is in the format of DCS Pn1 ! ~ xxxx ST Where xxxx is the hex value of the checksum.

Source: [VT420]

Erases all character positions in the specified rectangular area. Erased positions are set to SPACE with the visual attributes from the most recent SGR command. Hyperlinks are cleared on erased cells.

Pt, Pl, Pb, Pr define the rectangle (top, left, bottom, right). Defaults: Pt = 1, Pl = 1, Pb = last line, Pr = last column.

If Pb < Pt or Pr < Pl, DECERA is ignored. Coordinates are affected by origin mode (DECOM) but not by margins. Values exceeding page dimensions are clamped. The cursor does not move.

SOURCE: [VT420]

Invokes a macro. Pn specifies the macro number. If Pn is not 0..63, no action is taken.

SOURCE: [VT420]

NON-STANDARD EXTENSION (Deprecated)
Defaults: Ps1 = 255 Ps2 = 0
Indicates that a font block is following. Ps1 indicates the font slot to place the loaded font into. This must be higher than the last default defined font (See CSI sp D for list of predefined fonts) Ps2 indicates font size according to the following table:

The DCS font string should be used instead as of CTerm 1.213

Defaults: Pn = 1
Inserts Pn blank columns into the scrolling region, starting at the column that has the cursor. Columns between the cursor and the right margin shift to the right. Columns shifted past the right margin are lost. The inserted columns are filled with SPACE using the current SGR attributes. Hyperlinks are cleared on inserted cells.

DECIC has no effect if the cursor is outside the scrolling margins. The cursor does not move.

SOURCE: [VT420]

Defaults: Pn = 1
Deletes Pn columns from the scrolling region, starting at the column that has the cursor. The remaining columns between the cursor and the right margin shift to the left. Blank columns are added at the right margin, filled with SPACE using the current SGR attributes. Hyperlinks are cleared on the new blank cells.

DECDC has no effect if the cursor is outside the scrolling margins. The cursor does not move.

SOURCE: [VT420]

Indicates the string is a loadable font. (CTerm 1.213)

p1 is a font slot number, which must be higher than the last default defined font (See CSI sp D for list of predefined fonts). <b64> is the base64 encoded font data. Font size is deduced from the size of the data. This replaces the now deprecated CSI = Ps1 ; Ps2 {

Defaults: p1 = 0 p2 = 0 Indicates the string is a sixel sequence.

p1 selects the vertical height of a single pixel. This may be overridden by the raster attributes command, and is deprecated. Supported values

p2 indicates if unset sixels should be set to the current background colour. If p2 is 1, positions specified as 0 remain at their current colour.

Any additional parameters are ignored.

The rest of the string is made up of sixel data characters and sixel control functions. Sixel data characters are in the range of ? (0x3f) to ~ (0x7e). Each sixel data character represents six vertical pixels. The data is extracted by subtracting 0x3f from the ASCII value of the character. The least significant bit is the topmost pixel.

SOURCE: [VT330/340]

pt is the intermediate and/or final characters of a control function to query the status of. The terminal will send a response in the format

DCS p1 $ r pt ST

p1 is 1 if the terminal supports querying the control function and 0 if it does not.

pt is the characters in the control function except the CSI characters.

SOURCE: [VT420]

Defaults: p2 = 0 p3 = 0

Sets a macro to be replayed using CSI Pn * z

p1 is the macro number to set, and must be between 0 and 63 inclusive.

If p2 is zero, the macro numbered p1 will be deleted before the new macro is set. If p2 is one, all macros are deleted before the new macro is set. If the macro is zero length, only the delete action is stored, you can’t store a zero-length macro.

If p3 is zero, the macro is defined using ASCII characters (0x20 - 0x7e and 0xa0 - 0xff only). Note that since ESC (0x1b) is not in this range, ASCII-mode macros cannot contain escape sequences; use hex-mode (p3 = 1) instead. If p3 is one, the macro is defined using hex pairs.

When the macro is defined using hex pairs, a repeat sequence may be included in the format of ! Pn ; D..D ; Pn specifies the number of repeats (default of one instance)+ D..D is the sequence of pairs to send Pn times. The terminating ; may be left out if the sequence to be repeated ends at the end of the string.

SOURCE: [VT420]

Specifies one or more palette redefinitions or queries.
pX is the palette index, and pY is the colour definition
Color format: rgb:R/G/B:: Where R, G, and B are a sequence of one to four hex digits representing the value of the red, green, and blue channels respectively.

If pY is ?, CTerm responds with the current colour for palette index pX in the form OSC 4;pX;rgb:RR/GG/BB ST where RR, GG, and BB are two hex digit colour values reflecting the 8-bit-per-channel storage precision.

SOURCE: [XTerm]

Resets palette entry to default. If the entire string is "104" (ie: no Ps present), resets all colours. Otherwise, only each index separated by a semicolon is reset. SOURCE: [XTerm]

Queries the default foreground color.
CTerm responds with OSC 10;rgb:RR/GG/BB ST where RR, GG, and BB are two hex digit color values.

SOURCE: [XTerm]

Queries the default background color.
CTerm responds with OSC 11;rgb:RR/GG/BB ST where RR, GG, and BB are two hex digit color values.

SOURCE: [XTerm]

Sets a hyperlink on subsequent text output. Text printed after this sequence will be associated with the given URI. An empty URI ends the hyperlink region.

The params field is a colon-separated list of key=value pairs. The id= parameter allows non-contiguous text runs to share the same hyperlink.

Only http, https, ftp, and ftps URIs are supported. Other schemes are silently ignored.

Users can open hyperlinks by clicking when BBS mouse capture is off, or by Ctrl+clicking when mouse capture is active.

SOURCE: https://gist.github.com/egmontkob/eb114294efbcd5adb1944c9f3cb5feda

SyncTERM responds with an APC string of the form APC SyncTERM:VER;version ST where version is the full version string of SyncTERM, either SyncTERM 1.7rc1 for release builds or SyncTERM 1.7b Debug (Sep 27 2025) for debug builds

Where Ps1 is a filename and Ps2 is the base64 encoded contents of the file. The named file is stored in the cache directory for the current connection.

Defaults: Ps = *
Ps is the glob(3) pattern to use matching files.
SyncTERM responds with an APC string with lines separated by newlines. The first line is always SyncTERM:C;L\n and for each matching file, a line in the form <Filename> TAB <MD5 sum> LF is sent (ie: "coolfont.fnt\t595f44fec1e92a71d3e9e77456ba80d1\n")

Where Pn is a font slot number (max 255) and Ps is a filename in the cache. This sets font slot Pn to use the specified font file.

Draws a PPM from the cache directory on the screen.
Ps1 is the filename and is required. Arguments for Ps are optional. The following options can be included (separated by semi-colons):

The PPM file may be raw (preferred) or text. SyncTERM does not support more than 255 values per colour channel and assumes it is correctly using the BT.709 gamma transfer.

Draws a JPEG XL from the cache directory on the screen.
Ps1 is the filename and is required. Arguments for Ps are optional. The following options can be included (separated by semi-colons):

Loads a PPM to a buffer. Ps0 is the filename

Loads a JPEG XL to a buffer. Ps0 is the filename

Loads a PBM to a buffer. Ps0 is the filename

Copies a portion of the screen into an internal pixel buffer for use with the Paste function. Defaults to copying the entire screen. All coordinates and dimensions are in pixels.

Pastes from the copied pixel buffer. Supports the same options as the Cache DrawPPM command except for the filename, and adds the B= option. All coordinates and dimensions are in pixels.

Queries support for the JXL image format.
SyncTERM will respond with a CTerm APC State Report of the form

CSI = 1 ; pR - n

pR is 0 if JXL support is not available, and 1 if it is.

Unlike conventional terminals where attributes are invisible state changes, Prestel/Mode 7 uses serial attributes. Control codes in the range 0x40–0x5F (accessed via ESC + character in Prestel mode, or raw bytes 0x80–0x9F as C1 controls, or via ESC in BEEB mode) occupy a character cell position on screen. The control code cell is displayed as either a space or a held mosaic character.

Serial attributes apply to all subsequent cells on the same row until changed by another control code. At the start of each new row, all attributes reset to their defaults: white alphanumeric text, black background, no flash, no conceal, no hold, contiguous mosaics, normal height.

Control code effects are split into before and after phases:

These are the decoded control values (0x40–0x5F range after ESC, or 0x80–0x9F as raw C1 bytes minus 0x40):

The alphanumeric color codes (0x41–0x47) switch to the G0 character set where bytes 0x20–0x7F display as normal text characters.

The mosaic color codes (0x51–0x57) switch to the G1 character set. In mosaic mode, characters in the ranges 0x20–0x3F and 0x60–0x7F are displayed as 2×3 block mosaic graphics (with bit 7 set in the stored character value). Characters 0x40–0x5F remain alphanumeric even in mosaic mode.

When a mosaic color change occurs, the control code cell would normally display as a space. With hold mosaics enabled (code 0x5E), the control code cell instead displays the last mosaic character that was output, preserving visual continuity across color changes.

Hold mode is cleared by: alphanumeric color codes, normal height, double height, and release mosaics.

Double-height mode (code 0x4D) causes characters on the current row to be rendered at twice their normal height, spanning two physical screen rows. The top half is rendered on the row containing the double-height code, and the bottom half on the row below.

Double-height tracking is complex:

Code 0x58 enables concealed mode. Concealed characters are stored normally but rendered with the foreground hidden (displayed as background color). The user can toggle reveal mode (in SyncTERM, via Alt-V) to show concealed content.

Concealment is cleared by any alphanumeric or mosaic color code.

In BBC Micro mode, three characters are translated to match the Mode 7 SAA5050 character set:

Per the specification, "for all cursor movements the first character of each row is regarded as contiguous with the last character of the previous row, and the top row is regarded as the row following the bottom row." This means all cursor movement wraps around the screen in Prestel mode.

Bytes 0x20–0x7F are printable (with mosaic translation as described above). Bytes 0x80–0x9F are treated as raw C1 serial attribute controls (value minus 0x40). Other undefined C0 bytes are ignored (section 2.6: "shall take no action on their receipt").

Unlike Prestel, BEEB mode scrolls the screen when cursor movement reaches the edges rather than wrapping around.

The key behavioral difference between Prestel and BEEB modes is cursor wrapping at screen edges:

Left/right wrapping to adjacent rows is the same in both modes.

In Prestel mode, ESC is followed by a character that is interpreted as a serial attribute code (the character value is used directly as the control code, range 0x40–0x5F for valid codes).

Additionally, Prestel supports a programming protocol for memory slot management:

In BEEB mode, ESC does NOT trigger serial attribute codes (unlike Prestel). Serial attributes in BEEB mode are delivered as raw C1 bytes (0x80–0x9F) which are translated to attribute codes by subtracting 0x40.

ESC in BEEB mode introduces VDU control sequences. Two multi-byte sequences are supported:

Prestel/Mode 7 rendering is handled specially in the bitmap driver (bitmap_con.c) because it requires features not available in the standard text rendering path:

The CIOLIB_BG_PRESTEL_TERMINAL flag distinguishes Prestel terminal mode from BEEB mode for double-height bottom-row handling: Prestel copies attributes from the row above, while BEEB uses the cell’s own attributes.

Bytes 32–127 and 160–255 are printable characters (unless listed above). Bytes in ranges 0–31 and 128–159 that are not listed above are ignored.

The Commodore 128 KERNAL handles several control codes differently from the C64. CTerm currently uses C64 behavior for most of these. The following codes differ between C64 and C128 hardware but are not yet differentiated in CTerm:

The 16 color control codes map to different palette indices depending on the screen mode.

Reverse video mode (byte 18 on, byte 146 off) swaps the foreground and background nibbles of the attribute byte for all subsequent characters. Byte 13 (Return) also disables reverse mode.

Two character sets are available per machine type:

The upper-case set contains upper-case letters and PETSCII graphics characters. The lower-case set contains both upper and lower-case letters.

In normal mode, printable bytes are stored directly as raw ATASCII values in the screen buffer. The font rendering maps these to the appropriate Atari glyphs.

In inverse (ESC) mode, bytes are translated to Atari screen codes before storage:

Byte 27 (ESC) enables inverse video mode. The next byte received is translated to a screen code (see above) and displayed using the inverse attribute (attr=1 instead of the normal attr=7). After displaying the inverse character, normal mode is automatically restored. The ESC byte itself is not displayed.

In ESC mode, byte 155 (Return) still functions as a control code. All other bytes are translated to screen codes and displayed in inverse.

All other byte values (including 0–26 except ESC, 32–124, 128–154, 160–252) are treated as printable characters and displayed using the ATASCII-to-screen-code translation described above.

The four cursor movement keys wrap differently than most terminals:

This matches verified Atari 8-bit hardware behavior.

Tab stops in ATASCII are set and cleared at individual column positions using bytes 159 (Set Tab) and 158 (Clear Tab). Default tab stops are at the standard 8-column intervals. The tab character (byte 127) advances to the next set tab stop; if no stop exists before the end of the line, it wraps to column 1 of the next row (scrolling if necessary).

BS, HT, LF, and CR are processed by the shared ctputs output path. VT and FF are handled explicitly before output and behave identically to LF (move down one row with scroll).

All sequences are two bytes: ESC followed by a single character, except ESC Y which takes two additional parameter bytes.

These are extensions specific to the Atari ST’s TOS operating system.

The color parameter for ESC b and ESC c is the low 4 bits of the byte following the command character (value & 0x0F), giving an index from 0 to 15 into the current mode’s palette.

In low resolution (40×25), the full 16-color palette is available:

In medium resolution (80×25), the default palette has 4 colors repeated across all 16 slots: White (0), Red (1), Green (2), Black (3), matching the Atari ST hardware where only 4 simultaneous colors were available.

In high resolution (80×25 mono), the default palette alternates White and Black across all 16 slots, matching the monochrome hardware.

The Atari ST VT52 mode uses the full 4-bit foreground and background nibbles when swapping for reverse video, unlike ANSI-BBS mode which only swaps the low 3 bits and preserves the bright/blink bits independently. In VT52 mode, ESC p swaps all 4 bits of the foreground nibble with all 4 bits of the background nibble.