Linux Special Devices

In general,

block devices : are devices that store or hold data

character devices : can be thought of as devices that transmit or transfer data.

For example, diskette drives, hard drives and CD-ROM drives are all block devices while serial ports, mice and parallel printer ports are all character devices.

/dev/ttyS0 (First communications port, COM1)

First serial port (mice, modems).

/dev/psaux (PS/2)

PS/2 mouse connection (mice, keyboards).

/dev/lp0 (First printer port, LPT1)

First parallel port (printers, scanners, etc).

/dev/dsp (First audio device)

The name DSP comes from the term digital signal processor, a specialized processor chip optimized for digital signal analysis. Sound cards may use a dedicated DSP chip, or may implement the functions with a number of discrete
devices. Other terms that may be used for this device are digitized voice and PCM.

/dev/usb (USB Devices)

This subdirectory contains most of the USB device nodes. Device name allocations are fairly simplistic so no elaboration is be necessary.

/dev/sda (C:\, SCSI device)

First SCSI device (HDD, Memory Sticks, external mass storage devices such as CD-ROM drives on laptops, etc).

/dev/scd (D:\, SCSI CD-ROM device)

First SCSI CD-ROM device.

/dev/js0 (Standard gameport joystick)

First joystick device.

Devices are defined by type, such as 'block' or 'character', and 'major' and 'minor' number. The major number is used to categorize a device and the minor number is used to identify
a specific device type.