diff --git a/lec13/forktest.c b/lec13/forktest.c
new file mode 100644
index 0000000000000000000000000000000000000000..91dc9b6a292764264358501efd5f93a4d9d22f06
--- /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..9843a016b828ffd334923cb168ab3449651f96d1
--- /dev/null
+++ b/lec13/lsout.txt
@@ -0,0 +1 @@
+-rw-r--r-- 1 pcc022 pcc 104  1월 25 15:19 test.c
diff --git a/lec13/lsoutierr.txt b/lec13/lsoutierr.txt
new file mode 100644
index 0000000000000000000000000000000000000000..1cd2a912af8c49ac61f697cbab392c5970064af3
--- /dev/null
+++ b/lec13/lsoutierr.txt
@@ -0,0 +1,2 @@
+ls: cannot access 'zzz': No such file or directory
+-rw-r--r-- 1 pcc022 pcc 104  1월 25 15:19 test.c
diff --git a/lec13/output.txt b/lec13/output.txt
new file mode 100644
index 0000000000000000000000000000000000000000..e965047ad7c57865823c7d992b1d046ea66edf78
--- /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..f5243a2ce97907e42bafc91a5b791750e6f159cb
--- /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"));
+}
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..5264c6e5ecbf228c6499297518ba06f8003d223e
--- /dev/null
+++ b/lec13/threadtest.c
@@ -0,0 +1,35 @@
+#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(10000); 
+		fn_s(); 
+	}
+	return 0;
+
+}
+
+
+int main()
+{
+	pthread_t thread1;
+	int result1;
+	pthread_create(&thread1, NULL, run, NULL );
+	pthread_join(thread1,(void **) &result1);
+	printf("Thread return %d at the end\n", result1);
+}
+