diff --git a/lec12/Makefile.2 b/lec12/Makefile.2
new file mode 100644
index 0000000000000000000000000000000000000000..9dbc9c09dc0845adea23244859e4ce1da717d171
--- /dev/null
+++ b/lec12/Makefile.2
@@ -0,0 +1,8 @@
+main: main.o fx_s15_16.o
+	cc main.o fx_s15_16.o -o main
+main.o: main.c fx_head.h fx_s15_16.h
+	cc -c main.c
+fx_s15_16.o: fx_head.h fx_s15_16.c
+	cc -c fx_s15_16.c
+clean:
+	rm main *.o *.out
diff --git a/lec13/forktest.c b/lec13/forktest.c
new file mode 100644
index 0000000000000000000000000000000000000000..9223066460396a0f3130b96f59011ea407ed39b3
--- /dev/null
+++ b/lec13/forktest.c
@@ -0,0 +1,17 @@
+#include <stdio.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+int main()
+{
+	int a = 0; 
+	pid_t pid ,pid2;
+       	pid = fork(); 
+	pid2 = fork(); 
+	for (int i = 0; i < 100; i++)
+	{
+		sleep(1);
+		if (pid == 0)	
+			printf("PID %d : PID2 %d : A=%d : i=%d : \n", pid, pid2,  a++, i);
+	}
+}
diff --git a/lec13/lserr.txt b/lec13/lserr.txt
new file mode 100644
index 0000000000000000000000000000000000000000..06488f2516e233b2d10218765d8ae6ba476cf386
--- /dev/null
+++ b/lec13/lserr.txt
@@ -0,0 +1 @@
+ls: cannot access 'zzz': No such file or directory
diff --git a/lec13/lsout.txt b/lec13/lsout.txt
new file mode 100644
index 0000000000000000000000000000000000000000..f386eaf77adf57771d2d03c9f780a200d19089b2
--- /dev/null
+++ b/lec13/lsout.txt
@@ -0,0 +1 @@
+-rw-r--r-- 1 pcc004 pcc 127  1월 25 15:22 test.c
diff --git a/lec13/lsoutierr.txt b/lec13/lsoutierr.txt
new file mode 100644
index 0000000000000000000000000000000000000000..ec19ad56b920e55c7dc435c505eeb0a064f13000
--- /dev/null
+++ b/lec13/lsoutierr.txt
@@ -0,0 +1,2 @@
+ls: cannot access 'zzz': No such file or directory
+-rw-r--r-- 1 pcc004 pcc 127  1월 25 15:22 test.c
diff --git a/lec13/output.txt b/lec13/output.txt
new file mode 100644
index 0000000000000000000000000000000000000000..ce013625030ba8dba906f756967f9e9ca394464a
--- /dev/null
+++ b/lec13/output.txt
@@ -0,0 +1 @@
+hello
diff --git a/lec13/test.c b/lec13/test.c
new file mode 100644
index 0000000000000000000000000000000000000000..f0c7b0e10592ffa96216a604e717fa277240a5e9
--- /dev/null
+++ b/lec13/test.c
@@ -0,0 +1,7 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+int main(){
+	printf("System Call: %d\n", system("ls -li test.c zzz"));
+	return(100);
+}
diff --git a/lec13/th3.c b/lec13/th3.c
new file mode 100644
index 0000000000000000000000000000000000000000..c47f256b9fdebb3951b43e3f705da53f76ea7b96
--- /dev/null
+++ b/lec13/th3.c
@@ -0,0 +1,29 @@
+#include <stdio.h>
+#include <sys/types.h>
+#include <unistd.h>
+int bbb = 0;
+void fn_s()
+{
+    char bufff[10];
+    static int a = 0;
+    setvbuf(stdout, bufff, _IOFBF, 10);
+    printf("== %d %d ==",a++, bbb++);
+}
+
+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;
+    run((void *) 0);
+    printf("Thread return %d at the end\n", result1);
+}
diff --git a/lec13/thread2.c b/lec13/thread2.c
new file mode 100644
index 0000000000000000000000000000000000000000..d9761b6b6e81e4ddecb5d22f958efd084132da59
--- /dev/null
+++ b/lec13/thread2.c
@@ -0,0 +1,37 @@
+#include <pthread.h>
+#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++);
+}
+
+
+void *run (void *arg)
+{
+    printf("Hello world of POSXI threads.%d\n", (int) pthread_self() );
+    for (int i = 0; i < 100; i++)
+	{
+		usleep(100); 
+		fn_s(); 
+	}
+    return 0;
+
+}
+
+int main()
+{
+	pthread_t thread1;
+	int result1;
+	pthread_create(&thread1, NULL, run, NULL );
+	run((void *) 0); 
+	pthread_join(thread1, (void **) &result1);
+	printf("Thread return %d at the end\n", result1);
+}
+
diff --git a/lec13/threadtest.c b/lec13/threadtest.c
new file mode 100644
index 0000000000000000000000000000000000000000..3e8026c5a281035ca6bbe5bb05c71173c52c0042
--- /dev/null
+++ b/lec13/threadtest.c
@@ -0,0 +1,42 @@
+#include <pthread.h>
+#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++);
+}
+
+
+void *run (void *arg)
+{
+    printf("Hello world of POSXI threads.%d\n", (int) pthread_self() );
+	for (int i = 0; i < 100; i++)
+	{
+		sleep(1); 
+		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 );
+	// pthread_create(&thread2, NULL, run, NULL );
+	// pthread_create(&thread3, NULL, run, NULL );
+	pthread_join(thread1, &result1);
+	// pthread_join(thread2, &result2);
+	printf("Thread return %d at the end\n", result1);
+	// printf("Thread return %d at the end\n", result2);
+}
+
diff --git a/lec14/prtest.c b/lec14/prtest.c
new file mode 100644
index 0000000000000000000000000000000000000000..9188cf938b534479682fdc72c0633cc0538ff6b8
--- /dev/null
+++ b/lec14/prtest.c
@@ -0,0 +1,12 @@
+#include <stdio.h>
+
+int main()
+{
+	char a;
+	short b;
+	int c;
+	long long d;
+	
+	scanf("%d %d %d %d", &a, &b, &c, &d);
+	printf("%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..6f3fa9c3f787f889f6eb31d50228e128b4fd409c
--- /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..4308c85ac70f4c45168af5e3618237a3b59f20d5
--- /dev/null
+++ b/lec14/threadtest.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);
+}
+