Write a program to open a file for reading and print out its entire contents

Describe what the following Perl code does:

#!/usr/bin/perl
$numArgs = $#ARGV + 1;
print "$numArgs\n";
foreach $argnum (0 .. $#ARGV) {
print "$ARGV[$argnum]\n";
}

Explain the difference between a mutex and a semaphore? If you need to protect access to an increment operation which one would be the best choice?

Write a program to measure how long a context switch takes on the Unix operating system.