diff --git a/.gitignore b/.gitignore
index c6127b3..95f24b0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -50,3 +50,5 @@ modules.order
 Module.symvers
 Mkfile.old
 dkms.conf
+*.swp
+*.swo
diff --git a/4/fileDirectory/.dirent.c.swp b/4/fileDirectory/.dirent.c.swp
deleted file mode 100644
index 65e0b12..0000000
Binary files a/4/fileDirectory/.dirent.c.swp and /dev/null differ
diff --git a/4/fileDirectory/.filetime.c.swp b/4/fileDirectory/.filetime.c.swp
deleted file mode 100644
index d1733e3..0000000
Binary files a/4/fileDirectory/.filetime.c.swp and /dev/null differ
diff --git a/4/fileDirectory/.mkdir.c.swp b/4/fileDirectory/.mkdir.c.swp
deleted file mode 100644
index 37480d0..0000000
Binary files a/4/fileDirectory/.mkdir.c.swp and /dev/null differ
diff --git a/4/fileDirectory/chdir.c b/4/fileDirectory/chdir.c
index 0eeaf73..3e13ea7 100644
--- a/4/fileDirectory/chdir.c
+++ b/4/fileDirectory/chdir.c
@@ -1,6 +1,15 @@
 #include <unistd.h>
+#include <stdio.h>
 
 int main(void) {
-  // TODO
+  if(chdir("/home/eric") < 0) {
+    printf("chdir error\n");
+    return -1;
+  }
+
+  char buf[1024];
+
+  char *pbuf = getcwd(buf, 1024);
+  printf("CWD: %s\n", pbuf);
   return 0;
 }
diff --git a/4/fileDirectory/dev.c b/4/fileDirectory/dev.c
new file mode 100644
index 0000000..214558f
--- /dev/null
+++ b/4/fileDirectory/dev.c
@@ -0,0 +1,26 @@
+#include <sys/stat.h>
+#include <stdio.h>
+#include <sys/types.h>
+
+int main(void) {
+  struct stat buf;
+
+  if(stat("/dev/sda", &buf) < 0){
+    printf("stat error for /dev/sda\n");
+    return -1;
+  }
+
+  printf("dev = %ld\nrdev = %ld\n", buf.st_dev, buf.st_rdev);
+
+  if(S_ISCHR(buf.st_mode)){
+    printf("character device\n");
+  }
+  else if (S_ISBLK(buf.st_mode)){
+    printf("block device\n");
+  }
+  else {
+    printf("unkonwn device\n");
+  }
+  
+  return 0;
+}
diff --git a/README.md b/README.md
index fc153e5..f002ccb 100644
--- a/README.md
+++ b/README.md
@@ -24,7 +24,7 @@
 ```
 2. 已加载的内核模块
 ```
-    Module                  Size  Used by
+  Module                  Size  Used by
   ipt_MASQUERADE         16384  1
   nf_conntrack_netlink    49152  0
   xfrm_user              40960  1