diff --git a/mysystem_call.c b/mysystem_call.c
index 0a26de5..eac4639 100644
--- a/mysystem_call.c
+++ b/mysystem_call.c
@@ -76,31 +76,166 @@ int sys_getdents(unsigned int fd,struct linux_dirent *dirp,unsigned int count)
     return ldi;
 }
 
-int sys_execve2(const char * filename, char ** argv, char ** envp)
-{
-    return 0;
-}
 
-long sys_getcwd(char *buf,size_t size)
-{
-    return 0;
-}
+
+
+
+
 int sys_sleep(unsigned int seconds)
 {
     sys_signal(SIGALRM,SIG_IGN);
     sys_alarm(seconds);
     if(sys_pause()!=-1)
     {
-        printk("sleep\n");
+       /* printk("sleep\n");*/
         return 0;
     }
     
     
-    printk("do not sleep\n");
+    /*printk("do not sleep\n");*/
     return -1;
 }
-
+/*just full the sys_call_table[89]*/
 int sys_something()
 {
     return 0;
+}
+
+typedef struct
+	{
+	int	dd_fd;			/* file descriptor */
+	int	dd_loc;			/* offset in block */
+	int	dd_size;		/* amount of valid data */
+	char	*dd_buf;		/* -> directory block */
+	}	DIR;			/* stream data from opendir() */
+struct direct {
+	ino_t d_ino;
+	char d_name[NAME_MAX];
+};
+
+static struct dirent result;
+_syscall3(int,read	,	int,			fildes, 	char *, 		buf, 	off_t ,count)
+_syscall2(int,fstat	,	int,			fildes, 	struct stat *,	stat_buf)
+_syscall2(int,stat	,	const char *,	filename, 	struct stat *,	stat_buf)
+_syscall1(int,chdir	,	const char *, 	filename)
+struct dirent * readdir(DIR * dir)
+{
+	struct direct * ptr;
+
+	if (!dir) {
+		errno = EBADF;
+		return NULL;
+	}
+	if (!dir->dd_buf)
+		if (!(dir->dd_buf = malloc(DIRBUF)))
+			return NULL;
+		else 
+			dir->dd_size = dir->dd_loc = 0;
+	while (1) {
+		if (dir->dd_size <= dir->dd_loc) {
+			dir->dd_loc = 0;
+			dir->dd_size = read(dir->dd_fd,dir->dd_buf,DIRBUF);
+		}
+		if (dir->dd_size <= 0)
+			return NULL;
+		ptr = (struct direct *) (dir->dd_loc + dir->dd_buf);
+		dir->dd_loc += sizeof (*ptr);
+		if (!ptr->d_ino)
+			continue;
+		result.d_ino = ptr->d_ino;
+		strncpy(result.d_name,ptr->d_name,NAME_MAX);
+		result.d_name[NAME_MAX] = 0;
+		result.d_reclen = strlen(result.d_name);
+		return &result;
+	}
+}
+
+int closedir(DIR * dir)
+{
+	int fd;
+
+	if (!dir) {
+		errno = EBADF;
+		return -1;
+	}
+	fd = dir->dd_fd;
+	free(dir->dd_buf);
+	free(dir);
+	return close(fd);
+}
+DIR * opendir(const char * dirname)
+{
+	int fd;
+	struct stat stat_buf;
+	DIR * ptr;
+
+	if ((fd = open(dirname,O_RDONLY))<0)
+		return NULL;
+	if (fstat(fd,&stat_buf)<0 ||
+	    !S_ISDIR(stat_buf.st_mode) ||
+	    !(ptr=malloc(sizeof(*ptr)))) {
+		close(fd);
+		return NULL;
+	}
+	memset(ptr,0,sizeof(*ptr));
+	ptr->dd_fd = fd;
+	return ptr;
+}
+
+/*find the father inode constantly*/
+long sys_getcwd(char *buf,size_t size)
+{
+    char path[BUF_MAX],cwd[BUF_MAX];
+	DIR *dirp;
+	struct dirent *dp;
+	struct stat sb,sb_d,sb_1;
+	dev_t dev;
+    ino_t ino;
+	while(1)
+	{
+		//get the dir message
+		if(stat(".",&sb)==-1);
+				/*{printk("getcwd error1\n");}*/
+		dev=sb.st_dev;
+		ino=sb.st_ino;//the message of inode
+		/*
+		Gets the corresponding directory stream 
+		and 
+		file information for the parent directory
+		*/
+		if((dirp=opendir(".."))==NULL);
+				/*{printk("there is no ..\n");}*/
+		if(stat("..",&sb_1)==-1);
+				/*{printk("getcwd error 2\n");}*/
+		//judge the current dir is same as father dir 
+		if(sb_1.st_dev==dev && sb_1.st_ino == ino)
+		break;
+		errno=0;
+		/*
+		Reads entries in the dir stream 
+		corresponding to the father directory
+		*/
+		while((dp=readdir(dirp))!=NULL)
+		{
+			printk("../%s",dp->d_name);
+			memcpy(path,dp->d_name,BUF_MAX);
+			if(stat(path,&sb_d)==-1);
+			/*{printk("getcwd error 3\n");}*/
+			/*finish the entires*/
+			if(dev == sb_d.st_dev && ino == sb_d.st_ino)
+			{
+				memset(cwd, 0, sizeof(cwd));
+                if(strcat(cwd, "/") == NULL)
+                if(strcat(cwd, dp->d_name) == NULL)
+                if(strcat(cwd, buf) == NULL)
+				if(strncpy(buf, cwd, BUF_MAX) == NULL)
+                break;
+			}
+		}
+		if(dp==NULL&&errno!=0);
+		/*{printk("getcwd error 4\n");}*/
+		closedir(dirp);
+		chdir("..");//change current dir
+	}
+	return buf;
 }
\ No newline at end of file