diff --git a/include/direntry.h b/include/direntry.h
new file mode 100644
index 0000000..6b1c945
--- /dev/null
+++ b/include/direntry.h
@@ -0,0 +1,41 @@
+typedef struct fileNode {
+    char *name = NULL;
+    int inode_number;
+    int permissions;
+    char *Symbolink;
+    struct treeNode *subdirectory;
+    struct fileNode *next;
+    void serialize(char* buffer) {
+        u_int64_t t = inode_number;
+        for (int j = 0; j < 8; j++){
+            buffer[j] = t & (((u_int64_t)1<<(8))-1);
+            t >>= 8;
+        }
+        strcpy(buffer+8, file_name);
+    }
+    void deserialize(char* buffer) {
+        inode_number = 0;
+        for (int j = 0; j < 8; j++)
+            inode_number = inode_number | (((u_int64_t)(unsigned char)buffer[j])<<(8*j));
+        strcpy(file_name, buffer+8);
+    }
+} FileNode;
+
+typedef struct {
+    int size;
+    FileNode **table;
+} HashTable;
+
+typedef struct treeNode {
+    char *dirName;
+    HashTable *contents;
+    struct treeNode *parent;
+    FileNode *self_info; //self fileNode infromation
+} TreeNode;
+
+/*root directory have its own initialization, so parent wont be NULL*/
+int fischl_add_entry(TreeNode *parent, int new_inode_number, const char *fileName, INode *new_inode);
+/*if want to use dir mode use the subdirectory treeNode pointer */
+//e.g. FileNode *Dirnode = fischl_find_entry(); can see file inside with Dirnode->subdirectory
+//e.g. go to the current Dirnode parent directory, use TreeNode *get_Dir_parent = Dirnode->subdirectory->parent;
+FileNode *fischl_find_entry(TreeNode *root, const char *path);
diff --git a/lib/direntry.cpp b/lib/direntry.cpp
new file mode 100644
index 0000000..85f0a69
--- /dev/null
+++ b/lib/direntry.cpp
@@ -0,0 +1,133 @@
+/*********************************Hash operation********************************************
+
+********************************************************************************************/
+// Hash operation
+unsigned int hash(HashTable *h, char *key) {
+    unsigned int hashval = 0;
+    for (; *key != '\0'; key++) hashval = *key + (hashval << 5) - hashval;
+    return hashval % h->size;
+}
+
+HashTable *createHashTable(int size) {
+    HashTable *newTable = (HashTable *)malloc(sizeof(HashTable));
+    newTable->size = size;
+    newTable->table = (FileNode **)malloc(sizeof(FileNode *) * size);
+    for (int i = 0; i < size; i++) newTable->table[i] = NULL;
+    return newTable;
+}
+
+FileNode *insertHash(HashTable *h, char *key, TreeNode *subdirectory) {
+    unsigned int hashval = hash(h, key);
+    FileNode *newNode = (FileNode *)malloc(sizeof(FileNode));
+    newNode->name = strdup(key);
+    newNode->subdirectory = subdirectory;
+    newNode->next = h->table[hashval];
+    h->table[hashval] = newNode;
+    return newNode;
+}
+
+FileNode *lookupHash(HashTable *h, char *key) {
+    unsigned int hashval = hash(h, key);
+    FileNode *node = h->table[hashval];
+    while (node != NULL) {
+        if (strcmp(node->name, key) == 0) return node;
+        node = node->next;
+    }
+    return NULL; // Not found
+}
+
+void freeHashTable(HashTable *table) {
+    if (table == NULL) return;
+
+    for (int i = 0; i < table->size; ++i) {
+        FileNode *current = table->table[i];
+        while (current != NULL) {
+            FileNode *temp = current;
+            current = current->next;
+            // free(temp->name);
+            // free(temp);
+        }
+    }
+    free(table->table);
+    free(table);
+}
+
+void freeTree(TreeNode *node) {
+    //printf("***********************FREE TREE %s**************************\n",node->dirName);
+    //printf("***********************FREE TREE **************************\n");
+    if (node == NULL) return;
+
+    if (node->contents != NULL) {
+        for (int i = 0; i < node->contents->size; ++i) {
+            FileNode *current = node->contents->table[i];
+            while (current != NULL) {
+                FileNode *temp = current;
+                current = current->next;
+
+                if (temp->subdirectory != NULL) {
+                    freeTree(temp->subdirectory);
+                }
+                // Free the FileNode if it's not a directory
+                printf("free who %s\n",temp->name);
+                free(temp->name);
+                free(temp);
+            }
+        }
+        //printf("free %s's hash table\n",node->dirName);
+        freeHashTable(node->contents);
+        //node->contents = NULL;
+    }
+    //printf("free directory %s\n",node->dirName);
+    free(node->dirName);
+    node->dirName = NULL;
+    free(node);
+    node = NULL;
+    //printf("***********************END**************************\n");
+}
+
+/*********************************Direntry operation******************************************
+
+********************************************************************************************/
+int fischl_add_entry(TreeNode *parent, int new_inode_number, const char *fileName, INode *new_inode){
+    char *Name = strdup(fileName);
+    TreeNode *newDir = NULL;
+    /*If directory, malloc TreeNode, and then create filenode that belongs to Parent hash table content*/
+    if ((new_inode->permissions & S_IFMT) == S_IFDIR) {
+        newDir = (TreeNode *)malloc(sizeof(TreeNode));
+        newDir->dirName = Name;
+        newDir->contents = createHashTable(20);//hasSize define 20
+        newDir->parent = parent;
+    }
+    FileNode *newFile = insertHash(parent->contents, Name, newDir); //newDir == NULL indicates it's a file
+    //assign INode *new_inode metadata to data member in FileNode structure
+    newFile->permissions = new_inode->permissions;
+    newFile->inode_number = new_inode_number;
+    //Diretory have its own file information, that is . here
+    if(newDir != NULL)
+        newDir->self_info = newFile;
+    //free(Name); cannot free name
+    return 0;
+}
+
+FileNode *fischl_find_entry(TreeNode *root, const char *path){
+    //support . and .. function
+    char *pathCopy = strdup(path);
+    char *segment = strtok(pathCopy, "/");
+    TreeNode *current = root;
+    FileNode *file = NULL;
+
+    while (segment != NULL && current != NULL) {
+        file = lookupHash(current->contents, segment);
+        if (file != NULL && file->subdirectory == NULL) {
+            free(pathCopy);
+            return file; //File found
+            //return current; return filenode
+        }
+        current = file ? file->subdirectory : NULL;
+        segment = strtok(NULL, "/");
+    }
+
+    free(pathCopy);
+    return file; // NULL if not found
+    //return current; return filenode
+}
\ No newline at end of file
diff --git a/lib/files.cpp b/lib/files.cpp
index f1f0087..9304fcb 100644
--- a/lib/files.cpp
+++ b/lib/files.cpp
@@ -2,45 +2,8 @@
 #include "files.h"
 #include <string.h>
 #include <sstream>
+#include "direntry.h"
 
-/*********************************************************************
-                Directory Entry definition and function
-
-
-*********************************************************************/
-struct DirectoryEntry {
-    u_int64_t inode_number;
-    char file_name[56];
-    void serialize(char* buffer) {
-        u_int64_t t = inode_number;
-        for (int j = 0; j < 8; j++){
-            buffer[j] = t & (((u_int64_t)1<<(8))-1);
-            t >>= 8;
-        }
-        strcpy(buffer+8, file_name);
-    }
-    void deserialize(char* buffer) {
-        inode_number = 0;
-        for (int j = 0; j < 8; j++)
-            inode_number = inode_number | (((u_int64_t)(unsigned char)buffer[j])<<(8*j));
-        strcpy(file_name, buffer+8);
-    }
-};
-//Directory collection
-typedef struct {
-    //DirectoryEntry entries[MAX_ENTRIES]; with tree structure
-    unsigned int num_entries;
-} Directory;
-/*
- *	fishcl_add_entry()
- *
- * adds a file entry to the specified directory, using the same
- * semantics as fishcl_find_entry(). It returns NULL if it failed.
- *
- */
-static int fishcl_add_entry(Directory *dir, unsigned int inode_number, const char *name){
-
-}
 
 FilesOperation::FilesOperation(RawDisk& disk_): disk(disk_) {
     inop.initialize(disk);