Based on figure above, the user program performs a series of WRITE calls interleaved with processing. Code segments 1, 2, and 3 refer to sequences of instructions that do not involve I/O. The WRITE calls are to an I/O program that is a system utility and that will perform the actual I/O operation. I/O operation labelled 4 prepares the actual I/O operation. I/O operation labelled 5 is to complete the I/O operation. Using your own words, discuss the program timing for the following executions: i. Without interrupts ii. Short I/O wait iii. Long I/O wait State one advantage OR one disadvantage for each execution.

Program Flow Control User Program 1/0 Program User Program I/O Program User Program I/O Program 1/O Command 10 110 Command WRITE Command WRITE WRITE END Interrupt Handler Interrupt Handler WRITE WRITE WRITE END END WRITE WRITE WRITE (a) No interrupts (b) Interrupts; short I/O wait (6) Interrupts; long I/O wait 1,2,3 - code segments = interrupt occurs during course of execution of user program 4-I/O preparation 5- code to complete I/O Program Flow of Control Without and With Interrupts