This document discusses the use of semaphores in NachOS. It provides an example class for initializing and using semaphores. Producers and consumers are created as threads that use semaphores to access shared resources, with the producer incrementing the "full" semaphore after producing data and decrementing the "empty" semaphore, while the consumer does the opposite. The main function initializes the empty and full semaphores and creates the producer and consumer threads.

1. Semaphore in nachos

2. Semaphore in NachOS This codec is example: class Semaphore { public: Semaphore(char* debugName, int initialValue); ~Semaphore(); void P(); void V(); }

3. This part of the code demonstrates the initialization of the function and a prompter uses the semaphore to assign the variables in a specific place. int a = 0; Semaphore *s; void sum(int p) { int t; s->P(); a++; t = a; s->V(); printf("%d : a = %d", p, t); }

4. Semaphore *full; Semaphore *empty; void consumer(int dummy) { while (1) { full->P(); consume the next unit of data empty->V(); } } void producer(int dummy) { while (1) { empty->P(); produce the next unit of data full->V(); } }

5. In the previous slide it appears since there is realized the process of the producer and the consumer and of since they are called the functions P () and V () to give the step to every process and in the following slide it appears since they get about themselves to call in the principal function.

6. void main() { empty = new Semaphore("empty", N); full = new Semaphore("full", 0); Thread *t = new Thread("consumer"); t->Fork(consumer, 1); t = new Thread("producer"); t->Fork(producer, 1); }

7. Video example http://www.youtube.com/watch?v=Kg9lQGdipZ4