Question

1:Explain what is an interrupt and its process.                                                                  

2:State any three difference between top-down and bottom-up design strategies

3:What is the difference between Interrupt and polling technique? Which one is preferable

and why?

Answer 1

1)

Interrupt is a special condition which stops the working of the processor, when an interrupt occurs processor suspends it's curtain working task and executes a sub-routine of that interrupt which defines purpose of that interrupt called Interrupt service routine (ISR)

Interrupt generally occurs when an external device wants to interact with processor

When an interrupt occurs:

- when an interrupt is occured, the processor stores the address of current program into stack(by pushing the Program counter (PC) value) as return address

-Then goes to ISR of interrupt and executes the sub-routine

-After that loads the PC with return address from stack(by using POP) and continues from where it is suspended.

2)

1. Top-down approach decomposes the bigger task into subtasks whereas bottom-up approach first solves the different basic parts of the task directly then combine those parts into a complete program.
2. Every submodule is separately processed in a top-down designing. In bottom-up designing implements the concept of the information hiding by examining the data to be encrypted .
3. The different modules in top-down designing don’t require much communication among themselves. Whereas in bottom-up designing needs communication between basic modules
4. There may be chance of redundancy in in top-bottom. There is no redundancy in bottom-top

3)

When Interrupt occurs it enables some status bits and the processor when it is free goes to excute those interrupts.

Where as polling is a protocol that cpu has to keep on checking whether the external device is ready for data transfer.

In case polling , lot of processor time is wasted which we cannot allow as it is very critical

So definitely interrupt technique is better