Input output hardware of operating system
- 1. Input & Output Hardware Operating Systems Input & Output 1CSE-2018
- 2. Overview What is I/O? Categories of I/O Devices Device drivers & Device controllers Communication in I/O devices Polling & Interrupts Input & Output 2CSE-2018
- 3. What is I/O Device ? An input device sends information to a computer system for processing, and an output device reproduces or displays the results of that processing Input & Output 3CSE-2018
- 4. Categories Block Devices Character Devices Input & Output 4CSE-2018
- 5. Block Devices Character Devices Driver communicates by sending entire block of data Ex- Harddisk ,Usb Cameras..etc Driver communicates by sending characters(Bytes,Octets) Ex- Serial ports, Parralel ports Input & Output 5CSE-2018
- 6. Device driver Device controllers Software modules that handles a particular device. OS needs it to handle all I/O devices. Works as interface b/w device & device drivers. It converts serial bit streams into block of bytes. Input & Output 6CSE-2018
- 7. Synchronous Vs Asynchronous OS CPU execution waits while I/O proceeds. I/O proceeds concurrently with CPU execution Input & Output 7CSE-2018
- 8. Communication to I/O devices Three approaches… Special Instruction I/O Memory-mapped I/O DMA (Direct Memory access) Input & Output 8CSE-2018
- 9. Special instruction I/O CPU instructions , specially made to control I/O devices. Memory-mapped I/O The device is connected directly to certain main memory locations OS allocates buffer in memory and informs I/O device to use that buffer to send data to the CPU. Memory mapped IO is used for most high-speed I/O devices like disks, communication interfaces. Input & Output 9CSE-2018
- 10. Direct Memory Access (DMA) DMA means CPU grants I/O module authority to read from or write to memory without involvement. DMA module itself controls exchange of data between main memory and the I/O device. Input & Output 10CSE-2018
- 11. Polling Polling is the simplest way for an I/O device to communicate with the processor. The I/O device simply puts the information in a Status register, and the processor must come and get the information. This is an inefficient method and much of the processors time is wasted on unnecessary polls. Input & Output 11CSE-2018
- 12. Interrupts An interrupt is a signal to the microprocessor from a device that requires attention. When the interrupting device has been dealt with, the CPU continues with its original task as if it had never been interrupted. Input & Output 12CSE-2018
Editor's Notes
- #2: Assumptions: Graduate level Operating Systems Making Choices about operation systems Why a micro-century? …just about enough time for one concept