Software 1 - Bitwise operations and Pipes(13)

administrivia

Web Page - http://www.cs.tau.ac.il/~efif/courses/Software1_Spring_03

Riddle

• Find three ways to change one character in the code bellow so that the resulting code will print 20 times the minus sign ('-').
  • Remember, you can change one character only for each solution.

  int i, n=20; for (i = 0; i < n; i--) printf("-");

Student Accounts

• bit-wise operations usage for flags handling
  • accounts.c

The Dining Philosophers - the setup

• Five philosophers are seated around a round table
• Each philosopher has a bowl of rice in front
• Between each philosopher and his neighbor is a chopstick
• Each philosopher thinks for a while, then gets hungry and wants to eat
• Eating rice requires 2 chopsticks
  • however there are only five chopsticks
  • at most 2 philosophers can be eating at the same time
• A philosopher may acquire only the chopsticks to his immediate left or right
• Once a philosopher possesses two chopsticks, he will eat for a while, then put both chopsticks back down on each side

The Dining Philosophers - the problem

• Find a solution so that
  • deadlock does not occur
  • each philosopher gets to eat fairly often

The Dining Philosophers - the code

• diners.c