diff --git a/bac2/os/chap2/ex5.c b/bac2/os/chap2/ex5.c
index 06af55c..f1c2fad 100644
--- a/bac2/os/chap2/ex5.c
+++ b/bac2/os/chap2/ex5.c
@@ -1,41 +1,44 @@
-#include <stdlib.h>
 #include <stdio.h>
+#include <stdlib.h>
 
-struct node{
-	struct node* prev;
+typedef struct Node* LIFO;
+
+struct Node{
+	struct Node* prev;
 	void* data;
 };
 
-typedef struct node* LIFO; 
-
-LIFO* mklifo ();
-void push(LIFO* lst , void*);
-void* pop(LIFO* lst);
+LIFO mklifo();
+void push(LIFO*, void*);
+void* pop(LIFO*);
 
 int main(void)
 {
-	char* t = "test";
-	LIFO* lifo = mklifo();
-	push(lifo, t);
-	printf("%s", (char *)pop(lifo));
-	
+	int a = 5;
+	int b = 12;
+	LIFO lifo = mklifo();
+
+	push(&lifo, &a);
+	push(&lifo, &b);
+	int *c = pop(&lifo);
+	int *d = pop(&lifo);
+
+	printf("%d\n", *c);
+	printf("%d\n", *d);
 }
 
-LIFO *mklifo (){
-	LIFO* ret = malloc(sizeof(struct node));
-	return ret;
+LIFO mklifo(){
+	return calloc(1, sizeof(struct Node));
 }
 
-void push(LIFO *lst , void *el){
-	LIFO* next = mklifo();
+void push(LIFO* lst, void* el){
+	LIFO next = mklifo();
 	(*lst)->data = el;
-	(*next)->prev = *lst;
-	lst = next;
+	next->prev = *lst;
+	*lst = next;
 }
 
-void *pop(LIFO *lst){
-	void* el;
-	(*lst)->data = el;
+void *pop(LIFO* lst){
 	*lst = (*lst)->prev;
-	return el;
+	return (*lst)->data;
 }
diff --git a/bac2/os/chap2/ex5.o b/bac2/os/chap2/ex5.o
index 77ac7fe..025a4bd 100644
Binary files a/bac2/os/chap2/ex5.o and b/bac2/os/chap2/ex5.o differ
diff --git a/bac2/os/chap2/ex6.c b/bac2/os/chap2/ex6.c
new file mode 100644
index 0000000..d896d87
--- /dev/null
+++ b/bac2/os/chap2/ex6.c
@@ -0,0 +1,53 @@
+#include <stdlib.h>
+#include <stdio.h>
+
+
+typedef struct node{
+	void* data;
+	struct node* next;
+} NODE;
+
+//Could be only head but it allows a complexity of O(1) instead of O(n) for insertion (where n would be the size of the chain)
+typedef struct {
+	NODE* head;
+	NODE* tail;
+} FIFO;
+
+FIFO mkfifo ();
+void enqueue(FIFO *lst ,void* el);
+void* dequeue(FIFO *lst);
+
+int main(void)
+{
+	int a = 5;
+	int b = 12;
+	FIFO fifo = mkfifo();
+
+	enqueue(&fifo, &a);
+	enqueue(&fifo, &b);
+	int *c = dequeue(&fifo);
+	int *d = dequeue(&fifo);
+
+	printf("%d\n", *c);
+	printf("%d\n", *d);
+	
+}
+
+FIFO mkfifo (){
+	return (FIFO) {NULL, NULL};
+}
+
+void enqueue(FIFO *lst ,void *el){
+	NODE *new = calloc(1, sizeof(NODE));
+	new->data = el;
+	if(lst->tail != NULL)
+		lst->tail->next = new;
+	lst->tail = new;
+	lst->head = lst->head == NULL ? new : lst->head;
+}
+
+void* dequeue(FIFO *lst){
+	void* ret = lst->head->data;
+	lst->head = lst->head->next;
+	return ret;
+}