CharacterGeräte

CharacterGeräte, or character devices, are a class of device files used in Unix-like operating systems to provide unbuffered, sequential I/O streams between user processes and hardware drivers. Unlike block devices, which expose random-access blocks of data and rely on buffering, character devices transfer data as a stream of characters with minimal processing by the kernel. Access is through standard system calls such as open, read, and write, and the device driver implements the behavior for each device.

Character devices cover interfaces such as terminals and serial ports. Examples include /dev/ttyS0 (a serial line), /dev/pts/* (pseudo-terminals created for terminal emulation), and /dev/console. Virtual and special devices like /dev/null and /dev/random are also character devices. These devices typically present a simple byte-oriented interface, with data arriving or being consumed character by character.

Management and identification: In Unix-like systems, character devices are represented by character special files, identified by major and minor numbers that select the driver and the device instance. They are created by the kernel during system boot or on demand by udev, with permissions controlling access. Programs interact with them through file descriptors and I/O system calls; device-specific operations may be exposed via ioctl or other interfaces.

See also: Block devices, POSIX I/O, Device file, Unix-like operating systems.