Answer:
Although some devices can be controlled using nothing but their I/O regions, most real devices are a bit more complicated than that. Devices have to deal with the external world, which often includes things such as spinning disks, moving tape, wires to distant places, and so on. Much has to be done in a time frame that is different from, and far slower than, that of the processor. Since it is almost always undesirable to have the processor wait on external events, there must be a way for a device to let the processor know when something has happened.
That way, of course, is interrupts. An interrupt is simply a signal that the hardware can send when it wants the processor's attention. Linux handles interrupts in much the same way that it handles signals in user space. For the most part, a driver need only register a handler for its device's interrupts, and handle them properly when they arrive. Of course, underneath that simple picture there is some complexity; in particular, interrupt handlers are somewhat limited in the actions they can perform as a result of how they are run.
Creating a letter head is very simple. However, you need to do some planning. You are required to pick a size and shape accordingly. I would prefer a landscape oriented rectangle. Select a theme appropriate and consistent with the traits of you company. Personalize with a simple and sleek image that can be printed easily if necessary. Select a font that is bold enough, readable, and eye catching. You can include items like a slogan, a name, phone numbers, address, email address, a link to you web address and the established dates.
1.mouse input
2.keyboard input
3.monitor output
4.speakers output
5.printer output , and input if has scanner
5.microphone input
Compute unified device architecture
