Drivers

• Drivers are group of files that enable one or more hardware device to communicate with the computer's operating system.
• Without drivers the computer not be able to send and receive data correctly to the hardware devices such as printer.
• If appropriate driver is not installed, the device may not perform properly.
• A driver communicates with the device through the computer bus or communications subsystem to which the hardware connects.

Working process

• The driver, which was written by the same company that designed and manufactured the device.
• So that it knows how to communicate with the device hardware to get the data.
• After the driver gets the data from the device, it returns the data to the operating system, which returns it to the application.

• Not all drivers communicate directly with a device.
• They just manipulate the request and pass the request along to drivers that are lower in the stack.

Types

Block device driver

• Block device drivers support devices that handle fixed rather than variable amounts of data and access physically addressable storage media or support file system access.
• Hard disks and flash memory are common types of block devices.

Character device driver

• A character device typically transfers data to and from a user application.
• They behave like pipes or serial ports, instantly reading or writing the byte data in a character-by-character stream.
• Line printers, interactive terminals, and graphics displays are character device.

Network device driver

• A network device driver is a device driver that enables a network device to communicate between the computer and operating system as well as with other network computers and network devices.
• It receive and transmit data packets on hardware interface that connect to external systems, and provide a uniform interface that network protocols can access.
• Network adapter are network devices.

Pseudo device driver

• Not all device drivers control physical hardware, such type of drivers are called pseudo driver.
• These drivers do not operate on a bus.
• Pseudo drivers are pty terminal drivers are used in remote login.

Advantages

• It simplifies the programming by acting as a layer between hardware device and application or operating system.
• A higher level application code can be written for a specific hardware device.
• It accept generic high level commands and break them into low level device specific command according to device.
• It gives security to protect the operating system running at user level.

Disadvantages

• Real time system need to guarantee that certain workloads should be complete a specific time.
• Direct memory is not possible.
• Each device driver's code may be run on different execution context which make the resource counting difficult.