1.
a.
Fast and efficient
b.
Reduce cpu wait,because they can find instruction from caches.
c.
expensive
d.
Because caches can't always save data,so we need a device to keep our data consistent.
2.
a.
It reads commands from data and executes them to turn them into several system calls.
b.
An interrupt handler is called to deal with the cause of the interrupt;control is then returned to the interrupted context and instruction. A trap is a software-generated interrupt. An interrupt can be used to signal the completion of an I/O to obviate the need for device polling.
A trap can be generated intentionally by a user program. It can be used to call operating system routines or to catch arithmetic errors.
3.
Each device controller has a local buffer and a command register. It communicates with the CPU by interrupts. A device's controller plays an important role in the operation of that device; it functions as a bridge between the device and the operating system.
A CPU uses complex algorithms and programming to interpret signals and code.A CPU retrieves information from the code within programs. It reads it to understand what the code is for, and then it executes the instructions.
They use binary and digital codes.
4.
An instruction cycle is the basic operation cycle of computer. It is the process by a computer retrieves an instruction from its memory,This cycle will be repeated continuously by CPU.