diff --git a/Makefile b/Makefile
index 9697cba..5fb4ec5 100644
--- a/Makefile
+++ b/Makefile
@@ -4,7 +4,7 @@ CFLAGS = -Iinc -pthread -lrt
 VPATH = src
 
 OBJECTS := %.o list.o producer.o transformer.o consumer.o
-EXECUTE := main.out test.out
+EXECUTE := main.out #test.out
 
 .PHONY: all clean
 
diff --git a/inc/consumer.hpp b/inc/consumer.hpp
index 99e2815..d5e7d7f 100644
--- a/inc/consumer.hpp
+++ b/inc/consumer.hpp
@@ -1,2 +1,8 @@
 
-void consumer ();
\ No newline at end of file
+/*
+   consumer:
+      Unlinks blocks from list2,
+      Consumes them,
+      Links them to freelist
+*/
+void *consumer (void *);
\ No newline at end of file
diff --git a/inc/globals.hpp b/inc/globals.hpp
index 3c04cd4..d4a6ad4 100644
--- a/inc/globals.hpp
+++ b/inc/globals.hpp
@@ -4,4 +4,9 @@
 extern block memory[N];
 // create the three lists
 extern list lists[3];
-extern list *freelist, *list1, *list2;
\ No newline at end of file
+extern list *freelist, *list1, *list2;
+
+// count semaphores
+extern sem_t semfl, seml1, seml2;
+// binary semaphores
+extern sem_t mutfl, mutl1, mutl2;
\ No newline at end of file
diff --git a/inc/list.hpp b/inc/list.hpp
index 9cbcd78..a5eb338 100644
--- a/inc/list.hpp
+++ b/inc/list.hpp
@@ -20,5 +20,4 @@ void   list_link   (list *l, block *b);
 //   list_init:   links an array of blocks onto the end of a list
 void   list_init   (list *l, block *m, int size);
 //   list_print:  prints a list
-void   list_print  (list *l);
-void   list_concise(list *l);
\ No newline at end of file
+void   list_print(list *l, bool verbose = false);
\ No newline at end of file
diff --git a/inc/producer.hpp b/inc/producer.hpp
index 6198cf5..1d563be 100644
--- a/inc/producer.hpp
+++ b/inc/producer.hpp
@@ -1,2 +1,8 @@
 
-void producer ();
\ No newline at end of file
+/*
+   producer:
+      Unlinks blocks from freelist,
+      Produces them,
+      Links them to list1
+*/
+void *producer (void *);
\ No newline at end of file
diff --git a/inc/transformer.hpp b/inc/transformer.hpp
index 15a543e..d11e4aa 100644
--- a/inc/transformer.hpp
+++ b/inc/transformer.hpp
@@ -1,2 +1,10 @@
 
-void transformer ();
\ No newline at end of file
+/*
+   transformer:
+      Unlinks block x from list1
+      Unlinks block y from freelist
+      Uses block x to generate block y's data
+      Links block x to freelist
+      Links block y to list2
+*/
+void *transformer (void *);
\ No newline at end of file
diff --git a/src/consumer.cpp b/src/consumer.cpp
index 30254d4..cd2ed4e 100644
--- a/src/consumer.cpp
+++ b/src/consumer.cpp
@@ -1,9 +1,29 @@
+#include <semaphore.h>
+#include <unistd.h>
 #include "list.hpp"
-#include "globals.hpp"
+#include "globals.hpp" // freelist list1 list2
 #include "consumer.hpp"
 
-void consumer () {
-   block* c = list_unlink(list2);
-   //TODO: consume information in block c
-   list_link(freelist, c);
-}
\ No newline at end of file
+int consume(block* c);
+
+void *consumer (void *) {
+   while (true) {
+      sem_wait(&seml2); // decrease seml2
+      sem_wait(&mutl2);
+      block* c = list_unlink(list2);
+      sem_post(&mutl2);
+      //* consume information in block c
+      consume(c);
+      sem_wait(&mutfl);
+      list_link(freelist, c);
+      sem_post(&mutfl);
+      sem_post(&semfl); // increase freelist
+   }
+   return nullptr;
+}
+
+int consume(block *c) {
+   c->data = -c->data;
+   usleep(75);
+   return 0;
+}
diff --git a/src/list.cpp b/src/list.cpp
index a1a2b49..48d74fd 100644
--- a/src/list.cpp
+++ b/src/list.cpp
@@ -60,7 +60,8 @@ void list_init (list *l, block *m, int size) {
 }
 
 // YAML-like, because I like YAML
-void list_print(list *l) {
+
+void print_verbose(list *l) {
    if (!l) return;
    std::printf("l_%p:\n  - start:  '%p',\n  - end:    '%p',\n  - length: '%d',\n  - blocks:",l,l->start,l->end,l->length);
    block* b = l->start;
@@ -73,17 +74,21 @@ void list_print(list *l) {
       std::printf(" []\n");
    }
 }
-
-void list_concise (list *l) {
+// l_[addr]{size}: {element:value, ...}
+void print_concise(list *l) {
    if (!l) return;
-   std::printf("%lx: {", (__uint64_t)l&0xffff);
+   std::printf("l_%lx{%d}: {", (long int)l&0xffff, l->length);
    block *b = l->start;
    if (b) {
       do {
-         std::printf("%lx:%d, ", (__uint64_t)b&0xfff, b->data);
+         std::printf("%lx:%d, ", (long int)b&0xfff, b->data);
       } while (b = b->next);
       std::printf("\b\b} \n");
    } else {
       std::printf("}\n");
    }
+}
+
+void list_print(list *l, bool verbose) {
+   (verbose?print_verbose:print_concise)(l);
 }
\ No newline at end of file
diff --git a/src/main.cpp b/src/main.cpp
index 8fa432b..4102cc1 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -1,8 +1,13 @@
-#include <cstdint>
-#include <cstdio>
+#include <semaphore.h>
+#include <pthread.h>
+#include <unistd.h>
+#include <stdint.h>
+#include <stdio.h>
 #include "list.hpp"
 #include "globals.hpp"
 #include "producer.hpp"
+#include "consumer.hpp"
+#include "transformer.hpp"
 
 // Create all of memory
 block memory[N] = {0};
@@ -10,9 +15,45 @@ block memory[N] = {0};
 list lists[3] = {0};
 list *freelist = &lists[0], *list1 = &lists[1], *list2 = &lists[2];
 
+// count semaphores
+sem_t semfl, seml1, seml2;
+// binary semaphores
+sem_t mutfl, mutl1, mutl2;
+
 int main (int argc, char* argv[]) {
    // initialize the freelist
    list_init(freelist, memory, N);
-   //TODO: Use pthreads to split execution
+
    //TODO: Implement a semaphore solution to the problem
+   sem_init(&semfl, 0, freelist->length);
+   sem_init(&seml1, 0, 0);
+   sem_init(&seml2, 0, 0);
+   sem_init(&mutfl, 0, 1);
+   sem_init(&mutl1, 0, 1);
+   sem_init(&mutl2, 0, 1);
+
+   //TODO: Use pthreads to split execution
+   // Make some pthreads
+   pthread_t thread1, thread2, thread3;
+
+   // Create thread1 as producer
+   pthread_create(&thread1, NULL, producer, NULL);
+
+   // Create thread2 as transformer
+   pthread_create(&thread2, NULL, transformer, NULL);
+
+   // Create thread3 as consumer
+   pthread_create(&thread3, NULL, consumer, NULL);
+
+   while (true) {
+      list_print(freelist);
+      list_print(list1);
+      list_print(list2);
+      sleep(1);
+   }
+   // Wait for them to finish
+   pthread_join(thread1, NULL);
+   pthread_join(thread2, NULL);
+   pthread_join(thread3, NULL);
+
 }
diff --git a/src/producer.cpp b/src/producer.cpp
index 5e83cfe..985622f 100644
--- a/src/producer.cpp
+++ b/src/producer.cpp
@@ -1,9 +1,32 @@
+#include <semaphore.h>
+#include <unistd.h>
 #include "list.hpp"
-#include "globals.hpp"
+#include "globals.hpp" // freelist list1 list2
 #include "producer.hpp"
 
-void producer () {
-   block* b = list_unlink(freelist);
-   //TODO: Produce information in block b
-   list_link(list1, b);
-}
\ No newline at end of file
+#define wait(x) sem_wait(&x)
+#define sgnl(x) sem_post(&x)
+
+void produce(block* b);
+
+void *producer (void *) {
+   while (true) {
+      wait(semfl); // wait for freelist not empty
+      wait(mutfl); // lock freelist
+      block *b = list_unlink(freelist);
+      sgnl(mutfl); // unlock freelist
+      //* Produce information in block b
+      produce(b);
+      wait(mutl1); // lock l1
+      list_link(list1, b);
+      sgnl(mutl1); // unlock l1
+      sgnl(seml1);
+   }
+   return nullptr;
+}
+
+void produce(block *b) {
+   b->data++;
+   usleep(65);
+   return;
+}
diff --git a/src/test.cpp b/src/test.cpp
index 93696cc..8af736d 100644
--- a/src/test.cpp
+++ b/src/test.cpp
@@ -1,5 +1,6 @@
-#include <cstdint>
-#include <cstdio>
+#include <semaphore.h>
+#include <stdint.h>
+#include <stdio.h>
 #include "list.hpp"
 #include "globals.hpp"
 #include "producer.hpp"
@@ -14,42 +15,47 @@ list *freelist = &lists[0],
      *list1 = &lists[1],
      *list2 = &lists[2];
 
+// count semaphores
+sem_t semfl, seml1, seml2;
+// binary semaphores
+sem_t mutfl, mutl1, mutl2;
+
 void producer_test();
 void transfer_test();
 void consumer_test();
 
 int main(int argc, char *argv[]) {
    list_init(freelist, memory, N);
-   list_concise(freelist);
-   producer_test();
-   transfer_test();
-   consumer_test();
+   list_print(freelist);
+   //producer_test();
+   //transfer_test();
+   //consumer_test();
 }
 
 void producer_test() {
    printf("Starting producer_test:\n");\
-   producer();
-   list_concise(freelist);
-   list_concise(list1);
-   list_concise(list2);
+   producer(NULL);
+   list_print(freelist);
+   list_print(list1);
+   list_print(list2);
    printf("Ending producer_test\n");
 }
 
 void transfer_test() {
    printf("Starting transfer_test:\n");
-   transformer();
-   list_concise(freelist);
-   list_concise(list1);
-   list_concise(list2);
+   transformer(NULL);
+   list_print(freelist);
+   list_print(list1);
+   list_print(list2);
    printf("Ending transfer_test\n");
 }
 
 void consumer_test() {
    printf("Starting consumer_test:\n");
-   consumer();
-   list_concise(freelist);
-   list_concise(list1);
-   list_concise(list2);
+   consumer(NULL);
+   list_print(freelist);
+   list_print(list1);
+   list_print(list2);
    printf("Ending consumer_test\n");
 }
 
diff --git a/src/transformer.cpp b/src/transformer.cpp
index 012239b..64768aa 100644
--- a/src/transformer.cpp
+++ b/src/transformer.cpp
@@ -1,11 +1,44 @@
+#include <semaphore.h>
+#include <unistd.h>
 #include "list.hpp"
-#include "globals.hpp"
+#include "globals.hpp" // freelist list1 list2
 #include "transformer.hpp"
 
-void transformer () {
-   block* x = list_unlink(list1);
-   block* y = list_unlink(freelist);
-   //TODO: use block x to produce info in y
-   list_link(freelist, x);
-   list_link(list2, y);
-}
\ No newline at end of file
+void transform(block* x, block* y);
+
+void *transformer (void *) {
+   block *x, *y;
+   while (true) {
+      sem_wait(&seml1); // decrease seml1
+      sem_wait(&mutl1);
+      x = list_unlink(list1);
+      sem_post(&mutl1);
+
+      sem_wait(&semfl); // decrease semfl
+      sem_wait(&mutfl);
+      y = list_unlink(freelist);
+      sem_post(&mutfl);
+
+      //* use block x to produce info in y
+      transform(x, y);
+
+      sem_wait(&mutfl);
+      list_link(freelist, x);
+      sem_post(&mutfl);
+      sem_post(&semfl);
+
+      sem_wait(&mutl2);
+      list_link(list2, y);
+      sem_post(&mutl2);
+      sem_post(&seml2);
+   }
+   return nullptr;
+}
+
+void transform(block *x, block *y) {
+   x->data ^= y->data;
+   y->data ^= x->data;
+   x->data ^= y->data;
+   usleep(55);
+   return;
+}