Direct Memory Access (DMA)
• Direct memory access (DMA) is a method that allows an input/output
(I/O) device to send or receive data directly to or from the main memory
without the intervention of CPU. The process is managed by a chip
known as a DMA controller (DMAC).
DMA
• DMA can save processing time and is a more efficient way
to move data from the computer's memory to other
devices.
• Direct memory access is a feature of computer systems
that allows certain hardware subsystems to access main
system memory, independent of the central processing
unit (CPU).
• A DMA channel enables a device to transfer data without
exposing the CPU to a work overload.
DEVICE DRIVER
• Device driver is a software program that controls a particular type
of hardware device that is attached to a computer. When buying
an operating system, many device drivers are built into the product.
• A device driver essentially allows smooth communication between a
connected hardware device and the operating system.
• A Special subroutine was written for each I/O device and it is called a
Device Driver.
• Hardware that uses a device driver to connect to a computer
includes Printers, Displays, CD-ROM readers, Network or Sound
cards, computer Mouse or Hard disks.
• Device drivers will instruct a computer on how to communicate
with each input/output (I/O) device through translating the
operating system's I/O instructions to a software language the
hardware device understands.
• More commonly known as a driver, a device driver or hardware
driver is a group of files that enable one or more hardware
devices to communicate with the computer's operating system.
Without drivers, the computer would not be able to send and
receive data correctly to hardware devices, such as a printer.
• Device Drivers are Hardware Dependent.
Classification of device drivers :
1. Character driver : This category deals with the character
devices i.e., which transfer data character-by-character.
Example : consoles, serial port, sensors etc.
2. Block driver : For the devices that transfer data by a block size
(thus called block devices), the corresponding driver is called
block device driver.
Example : CD-ROM, USB devices etc.
3. Network driver : The devices that allows us to connect to
a network and use the network interface services (called
network devices) have a network driver in place for them.
Example : Ethernet card, NIC (Network Interface Card) etc.
Applications of Device Drivers :
• Printers
• Video adapters
• Network cards
• Sound cards
• Mouse
• Keyboards
• USB
• Hard disk, CD-ROM, and floppy disk buses
• Image scanners
• Digital cameras
