269 lines
8.8 KiB
Groff
269 lines
8.8 KiB
Groff
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.TH CONSOLE 4
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.SH NAME
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console, keyboard, log \- system console
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.SH DESCRIPTION
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The TTY device driver manages two devices related to the main user
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interface, the system screen and the keyboard. These two together are
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named "the Console".
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.SS "The Screen"
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The screen of a PC can be managed by a Monochrome Display Adapter, a
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Hercules card, a Color Graphics Adapter, an Enhanced Graphics Adapter,
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or a Video Graphics Array. To the console driver these devices are
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seen as a block of video memory into which characters can be written to
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be displayed, an I/O register that sets the video memory origin to the
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character that is to be displayed on the top-left position of the
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screen, and an I/O register that sets the position of the hardware
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cursor. Each character within video memory is a two-byte word. The low
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byte is the character code, and the high byte is the "attribute byte",
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a set of bits that controls the way the character is displayed,
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character and background colours for a colour card, or
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intensity/underline/reverse video for monochrome.
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.PP
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These are the characteristics of the adapters in text mode:
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.PP
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.RS
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.nf
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.ta +15n +15n
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Adapter Usable memory Mono/Colour
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.ta +1n +15n +15n
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MDA 4K M
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Hercules 4K M
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CGA 16K C
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EGA 32K M or C
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VGA 32K M or C
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.fi
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.RE
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.PP
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MDA and Hercules are the same to the console driver, because the graphics
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mode of the Hercules is of no use to Minix. EGA and VGA are also mostly
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seen as the same in text mode. An EGA adapter is either a monochrome or a
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colour device depending on the screen attached to it. A VGA adapter can run
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in either monochrome or colour (grayscale) mode depending on how the Boot
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Monitor has initialized it.
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.PP
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The driver uses the video origin to avoid copying the screen contents when
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scrolling up or down. Instead the origin is simply moved one line. This is
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named "hardware scrolling", as opposed to copying memory: "software
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scrolling".
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.PP
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The video origin is also used to implement several virtual consoles inside
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the video memory of the adapter. Each virtual console gets a segment of
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video memory. The driver chooses which console to display by moving the
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video origin. Note that an MDA or Hercules adapter can only support one
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console. CGA can support up to four 80x25 consoles, and EGA and VGA can
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have eight. It is best to configure one less console to leave some video
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memory free so that hardware scrolling has some space to work in.
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.PP
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Character codes are used as indices into a display font that is stored in the
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adapter. The default font is the IBM character set, which is an ASCII
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character set in the low 128 codes, and a number of mathematical, greek,
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silly graphics, and accented characters in the upper 128 codes. This font
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is fixed in the MDA, Hercules and CGA adapters, but can be replaced by a
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user selected font for the EGA and VGA adapters.
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.PP
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A number of control characters and escape sequences are implemented by the
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driver. The result is upward compatible with the ANSI standard terminal.
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The
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.BR termcap (5)
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type is
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.BR minix .
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Normal characters written to the console are displayed at the cursor
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position and the cursor is advanced one column to the right. If an entire
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line is filled then the cursor wraps to the first column of the next line
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when the next character must be displayed. The screen is scrolled up if
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needed to start a new line. Some characters have special effects when sent
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to the console. Some even have arguments in the form of comma separated
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decimal numbers. These numbers default to the lowest possible value when
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omitted. The top-left character is at position (1, 1). The following
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control characters and escape sequences are implemented by the console:
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.PP
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.ta +10n +20n
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Sequence Name Function
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.in +31n
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.ti -30n
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^@ Null Ignored (padding character)
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.ti -30n
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^G Bell Produce a short tone from the speaker
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.ti -30n
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^H Backspace Move the cursor back one column, wrapping from the
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left edge up one line to the right edge
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.ti -30n
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^I Horizontal Tab Move to the next tab stop, with each tab stop at
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columns 1, 9, 25, etc. Wrap to the next line if necessary.
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.ti -30n
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^J Line Feed Move one line down, scrolling the screen up if
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necessary
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.ti -30n
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^K Vertical Tab Same as LF
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.ti -30n
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^L Form Feed Same as LF
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.ti -30n
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^M Carriage Return Move to column 1
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.ti -30n
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^[ Escape Start of an escape sequence
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.ti -30n
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^[M Reverse Index Move one line up, scrolling the screen down if
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necessary
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.ti -30n
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^[[\fIn\fPA Cursor Up Move the cursor up \fIn\fP lines
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.ti -30n
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^[[\fIn\fPB Cursor Down Move the cursor down \fIn\fP lines
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.ti -30n
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^[[\fIn\fPC Cursor Forward Move the cursor right \fIn\fP columns
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.ti -30n
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^[[\fIn\fPD Cursor Backward Move the cursor left \fIn\fP columns
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.ti -30n
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^[[\fIm\fP;\fIn\fPH Cursor Position Move the cursor to line \fIm\fP,
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column \fIn\fP
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.ti -30n
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^[[\fIs\fPJ Erase in Display Clear characters as follows:
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.br
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\fIs\fP = 0: From cursor to end of screen
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.br
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\fIs\fP = 1: From start of screen to cursor
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.br
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\fIs\fP = 2: Entire screen
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.ti -30n
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^[[\fIs\fPK Erase in Line Clear characters as follows:
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.br
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\fIs\fP = 0: From cursor to end of line
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.br
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\fIs\fP = 1: From start of line to cursor
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.br
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\fIs\fP = 2: Entire line
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.ti -30n
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^[[\fIn\fPL Insert Lines Insert \fIn\fP blank lines
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.ti -30n
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^[[\fIn\fPM Delete Lines Delete \fIn\fP lines
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.ti -30n
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^[[\fIn\fP@ Insert Characters Insert \fIn\fP blank characters
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.ti -30n
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^[[\fIn\fPP Delete Characters Delete \fIn\fP characters
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.ti -30n
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^[[\fIn\fPm Character Attribute Set character attribute as follows:
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.br
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\fIn\fP = 0: Normal (default) attribute
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.br
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\fIn\fP = 1: Bold (high intensity fg colour)
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.br
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\fIn\fP = 4: Underline (mono) / Cyan (colour)
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.br
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\fIn\fP = 5: Blinking
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.br
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\fIn\fP = 7: Reverse Video
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.br
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\fIn\fP = 30: Black foreground colour
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.br
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\fIn\fP = 31: Red
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.br
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\fIn\fP = 32: Green
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.br
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\fIn\fP = 33: Brown
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.br
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\fIn\fP = 34: Blue
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.br
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\fIn\fP = 35: Magenta
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.br
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\fIn\fP = 36: Cyan
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.br
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\fIn\fP = 37: Light Gray
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.br
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\fIn\fP = 39: Default fg colour (lt gray)
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.br
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\fIn\fP = 40\-47: Same for background colour
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.br
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\fIn\fP = 49: Default bg colour (black)
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.br
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Note: The "bold" versions of black, brown and lt gray become dark gray,
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yellow and white.
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.in -31n
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.PP
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The console device implements the following ioctl to copy a font into
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font memory on EGA and VGA adapters:
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.PP
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.RS
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.BI "ioctl(" fd ", TIOCSFON, u8_t " font "[256][32]);"
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.RE
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.PP
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Font memory consists of 256 character definitions of 32 lines per character
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and 8 pixels per line. The first line is the topmost line of the character.
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The leftmost pixel is lit if the most significant bit of a line is set, etc.
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How many lines are used depends on the current video mode. The 80x25 video
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mode used by Minix has an 8x16 character cell, 80x28 has 8x14 characters,
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and 132x43 or 132x50 has 8x8 characters. The boot variable
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.B console
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is used by both the Boot Monitor and the console driver to set the video
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mode, software scrolling on/off, and VGA screen blank timeout. See
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.BR boot (8).
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.SS "The Keyboard"
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The keyboard produces key codes for each key that is pressed. These keys
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are transformed into character codes or sequences according to the current
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keyboard translation table. The format of this table is described in
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.BR keymap (5).
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The character codes can be read from the console device unless they map to
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special hotkeys. The hotkeys are as follows:
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.PP
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.ta +17n
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Name Key Function
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.in +18n
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.ti -17n
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CTRL\-ALT\-DEL Send an abort signal to process 1 (init). Init then
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halts the system
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.ti -17n
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CTRL\-ALT\-KP-. Likewise for keypad period
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.ti -17n
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F1 Process table dump
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.ti -17n
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F2 Show memory map
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.ti -17n
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F3 Toggle software/hardware scrolling
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.ti -17n
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F5 Show network statistics
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.ti -17n
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CTRL\-F7 Send a quit signal to all processes connected to the console
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.ti -17n
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CTRL\-F8 Send an interrupt signal
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.ti -17n
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CTRL\-F9 Send a kill signal. If CTRL\-F8 or CTRL\-F7 don't get 'em,
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then this surely will. These keys are for disaster recovery. You would
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normally use DEL and CTRL\-\e to send interrupt and quit signals.
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.\" .ig VC
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.ti -17n
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ALT\-F1 Select virtual console 0 (/dev/console)
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.ti -17n
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ALT\-F2 Select virtual console 1 (/dev/ttyc1)
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.ti -17n
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ALT\-F(\fIn\fP+1) Select virtual console \fIn\fP
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(/dev/ttyc\fIn\fP)
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.ti -17n
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ALT\-Left Select previous virtual console
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.ti -17n
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ALT\-Right Select next virtual console
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.\" ..
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.in -18n
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.PP
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.\"XXX
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The keyboard map is set with the
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.B KIOCSMAP
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ioctl whose precise details are currently hidden in the
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.B loadkeys
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utility.
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.SS "Log device"
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The
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.B log
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device can be used by processes to print debug messages onto the console.
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The console is a terminal type device, so it is taken from processes when a
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session leader exits. This does not happen with the log device.
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.SH "SEE ALSO"
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.BR tty (4),
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.BR loadkeys (1),
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.BR keymap (5),
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.BR boot (8).
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.SH NOTES
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Output processing turns Line Feeds into CR LF sequences. Don't let this
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surprise you. Either turn off output processing or use one of the synonyms
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for LF.
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.SH AUTHOR
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Kees J. Bot (kjb@cs.vu.nl)
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.\" minor editing of man page by asw 07.08.96
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