Write a new system call getreadcount() for xv6 OS. The return type and parameters are: int getreadcount(void)
The call returns the total number of times the read() system call has been invoked since the time the kernel was booted. Note that the kernel does not keep a counter. You must add it.

Explain briefly why you cannot expect to find a previous version of every file with which you work.

What is a point-in-time measurement of system performance?

Write a program that uses a two-dimensional array to store the highest and lowest temperatures for each month of the year. the program should output the average high, average low, and the highest and lowest temper- atures for the year. your program must consist of the following functions: a. function getdata: this function reads and stores data in the two- dimensional array. b. function averagehigh: this function calculates and returns the average high temperature for the year. c. function averagelow: this function calculates and returns the aver- age low temperature for the year. d. function indexhightemp: this function returns the index of the highest high temperature in the array. e. function indexlowtemp: this function retur