Device Drivers

What are Device drivers? How are device drivers updated?
 Answer:-

Device drivers  are specialized programs that allow device such as mouse, printer, scanner or keyboard to communicate with the rest of the computer system.

Every device, such as a mouse or printer , that is connected to a computer system, has a special program associated with it. This program , called a device driver or simply a driver, works with the operating system to allow communication between the device and the rest of the computer system.
Each time the computer system is started, the operating system loads all the device drivers into memory.

Whenever a new device is added to a computer system, a new device driver must be installed before the device can be used .
Windows supplies hundreds of different device drivers with its system software. If a particular device driver is not included , the product's manufacturer will supply one.
Many time these drivers are available directly form manufacturer's website.

You probably never think abut the drivers in your computer.
However when your computer behaves unpredictably , you find updating your drivers solves your problems.
Windows makes it easy to update the drivers on your computer using Windows Update.

Process States and Transitions

List containing complete set of process states:
1. The process is executing in user mode.
2. The process is executing in kernel mode.
3. The process is not executing but is ready to run as soon as the kernel schedules it.
4. The process is sleeping and resides in main memory .
5. The process is ready to run , but swapper (process 0) must swap the process into main memory before the kernel can schedule it to execute.
6. The process is sleeping, and the swapper has swapped the process to secondary storage to make room for other processes in main memory.
7. The process is returning from the kernel to user mode ,but the kernel preemprts it and does a context switch to schedule another process.The distinction between this state and state 3 (ready to run) will be brought out shortly.
8. The process is newly created and is in a transition state ; the process exists, but it is not ready to run , nor is it sleeping . This state  is the start for all processes except process 0.
9. The process executed the exit system call and is in the zombie state. The process no longer exists , but it leaves a record containing an exit code and some timing statistics for its parent process to collect .The zombie state is the final state of a process.