Virtual Terminal Sequence3/29/2021
Now it offers a kernel space text mode emulation on any platform.The presence of the penguin graphic indicates this is a framebuffer console as opposed to text mode console.The user typically enters text with a computer keyboard and reads the output text on a computer monitor.
The Linux kernel supports virtual consoles consoles that are logically separate, but which access the same physical keyboard and display. The Linux console (and Linux virtual consoles) are implemented by the VT subsystem of the Linux kernel, and do not rely on any user space software. This is in contrast to a terminal emulator, which is a user space process that emulates a terminal, and is typically used in a graphical display environment. There are two main implementations: framebuffer and text mode. The framebuffer implementation is the default in modern Linux distributions, and together with kernel mode setting, provides kernel-level support for display hardware and features such as showing graphics while the system is booting. The legacy text mode implementation was used in PC-compatible systems with CGA, EGA, MDA and VGA graphics cards. Non- x86 architectures used framebuffer mode because their graphics cards did not implement text mode. The Linux console uses fixed-size bitmap, monospace fonts, usually defaulting to 8x16 pixels per character. These systems typically provide an alternative user interface (e.g. Virtual Terminal Sequence Serial Port ConsoleOther implementations of the Linux console include the Braille console to support refreshable Braille displays 7 and the serial port console. Some modern Linux-based systems have deprecated kernel based text-mode input and output, and instead show a graphical logo or progress bar while the system is booting, followed by the immediate start of a graphical user interface (e.g. X.Org Server on desktop distributions, or SurfaceFlinger on Android). The boot log includes information about detected hardware, and updates on the status of the boot procedure. At this point in time, the kernel is the only software running, and hence logging via user-space (e.g. Once the kernel has finished booting, it runs the init process (also sending output to the console), which handles booting of the rest of the system including starting any background daemons. On each virtual terminal, a getty process is run, which in turn runs binlogin to authenticate a user. Virtual terminals, like the console, are supported at the Linux kernel level. From the users point of view, this creates the illusion of several independent consoles. Linux 2.6 introduced the ability to load a different font for each virtual console (kernel versions predating 2.6 change the font only on demand). In text mode, the kernel sends a 2D array of characters to the video card, and the video card converts the characters to pixels for display. Code points in the text buffer and font are generally not the same as encoding used in text terminal semantics to put characters on the screen. The set of glyphs on the screen is determined by the current font. The text screen is handled by console.c and consolemap.c drivers. There is a utility for altering fonts and terminal encodings called consolechars. SVGATextMode helps to enable more complex text modes than the standard EGA and VGA modes. The comparable feature there, but for application software only, is the Win32 console. Also, NT systems use own text buffer format incompatible with VGA, which produces an overhead in hardware text modes.
0 Comments
Leave a Reply.AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |