diff --git a/lec13/threadtest.c b/lec13/threadtest.c
index 8b374619e4d1af455ff2d93a03a5082b68cffd01..7b7fb7f307d36c95676b42a4780dbb0ca46a71cd 100644
--- a/lec13/threadtest.c
+++ b/lec13/threadtest.c
@@ -8,7 +8,8 @@ int bbb = 0;
 void fn_s()
 {
 	static int a = 0; 
-    printf("== %d %d ==\n",a++, bbb++);
+	setvbuf(stdout, _IOFBF, NULL, 10);
+    	printf("== %.2d %.2d ==",a++, bbb++);
 }
 
 
diff --git a/lec14/mutextest.c b/lec14/mutextest.c
new file mode 100644
index 0000000000000000000000000000000000000000..4308c85ac70f4c45168af5e3618237a3b59f20d5
--- /dev/null
+++ b/lec14/mutextest.c
@@ -0,0 +1,48 @@
+#include <stdio.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <pthread.h>
+
+int bbb = 0; 
+
+void fn_s()
+{
+	static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
+    	static int a = 0; 
+    	printf("<= %d %d =>",a, bbb);
+    	pthread_mutex_lock(&mutex);
+	a++; bbb++;
+    	pthread_mutex_unlock(&mutex);
+}
+
+
+void *run (void *arg)
+{
+    printf("Hello world of POSXI threads.%d\n", (int) pthread_self() );
+    for (int i = 0; i < 1000000; i++)
+	{
+		//usleep(10000); 
+		fn_s(); 
+	}
+    return 0;
+
+}
+
+int main()
+{
+	pthread_t thread1;
+	pthread_t thread2;
+	pthread_t thread3;
+	int result1, result2, result3;
+
+	pthread_create(&thread1, NULL, run, NULL );
+	pthread_create(&thread2, NULL, run, NULL );
+	pthread_create(&thread3, NULL, run, NULL );
+	run((void *) 0); 
+	pthread_join(thread1, (void **) &result1);
+	pthread_join(thread2, (void **) &result2);
+	pthread_join(thread3, (void **) &result3);
+	printf("\nThread return %d at the end\n", result1);
+}
+
diff --git a/lec14/prtest.c b/lec14/prtest.c
new file mode 100644
index 0000000000000000000000000000000000000000..297d34147c8ce11aeedd824258986ebea3530fc7
--- /dev/null
+++ b/lec14/prtest.c
@@ -0,0 +1,11 @@
+#include <stdio.h>
+
+int main()
+{
+	char a;
+	short b;
+	int c;
+	long long d;
+	fscanf(stdin, "%d %d %d %d", &a, &b, &c, &d);
+	fprintf(stdout, "%d %d %d %d\n", a, b, c, d);
+}
diff --git a/lec14/th4.c b/lec14/th4.c
new file mode 100644
index 0000000000000000000000000000000000000000..13c319a9a2a40a9b1b29b6949592087e1dbb364a
--- /dev/null
+++ b/lec14/th4.c
@@ -0,0 +1,34 @@
+#include <stdio.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+int bbb = 0; 
+
+void fn_s()
+{
+	static int a = 0; 
+	printf("== %d %d ==",a++, bbb++);
+	fflush(stdout);
+}
+
+
+void *run (void *arg)
+{
+	printf("Hello world of POSIX threads.%d\n", (int) (0) );
+	for (int i = 0; i < 10; i++)
+	{
+		sleep(1); 
+		fn_s(); 
+	}
+	return 0;
+}
+
+int main()
+{
+	int result1;
+    	//char bufff[10]; 
+    	//setvbuf(stdout,bufff,  _IONBF, 10); 
+	run((void *) 0); 
+	printf("Thread return %d at the end\n", result1);
+}
+
diff --git a/lec14/threadtest.c b/lec14/threadtest.c
new file mode 100644
index 0000000000000000000000000000000000000000..5bafc580ee680ca25aa55a47350007147a0017e3
--- /dev/null
+++ b/lec14/threadtest.c
@@ -0,0 +1,45 @@
+#include <pthread.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+
+int bbb = 0; 
+
+void fn_s()
+{
+	static int a = 0; 
+    	printf("<= %.4d %.4d =>",a++, bbb++);
+	fflush(stdout);
+}
+
+
+void *run (void *arg)
+{
+	printf("Hello world of POSIX threads.%d\n", (int) pthread_self() );
+	for (int i = 0; i < 100; i++)
+	{
+		usleep(10000); 
+		fn_s(); 
+	}
+    return 0;
+
+}
+
+int main()
+{
+	pthread_t thread1;
+	pthread_t thread2;
+	pthread_t thread3;
+	int result1;
+	int result2;
+	pthread_create(&thread1, NULL, run, NULL );
+	printf("\nJUST AFTER THE CREATE\n");
+	run((void *) 0);
+	pthread_create(&thread2, NULL, run, NULL );
+	pthread_create(&thread3, NULL, run, NULL );
+	pthread_join(thread1, (void **) &result1);
+	pthread_join(thread2, (void **) &result2);
+	printf("\nThread return %d at the end\n", result1);
+	printf("Thread return %d at the end\n", result2);
+}
+