diff --git a/src/filesys/filesys.rs b/src/filesys/filesys.rs
index 3130ceb..866cc74 100644
--- a/src/filesys/filesys.rs
+++ b/src/filesys/filesys.rs
@@ -1,6 +1,89 @@
+use crate::simulator::disk;
 
 
+const FREE_MAP_SECTOR : i32 = 0;
+const DIRECTORY_SECTOR : i32 = 1;
+
 pub struct Filesys {
     pub free_map_file : Open_File, //Bit map of free disk blocks, represented as a file
     pub directory_file : Open_file //"Root" directory -- list of file names, represented as a file
+}
+
+impl Filesys {
+
+    /// Initialize the file system. If format = true, the disk has
+    /// nothing on it, and we need to initialize the disk to contain
+    /// an empty directory, and a bitmap of free sectors (with almost but
+    /// not all of the sectors marked as free).  
+    ///
+    /// If format = false, we just have to open the files
+    /// representing the bitmap and the directory.
+    ///
+    ///  ### parameters
+    /// 
+    /// -**format** should we initialize the disk?
+    pub fn init_filesys(format : bool) -> Filesys {
+        if format {
+            let free_map = bitmap::init_bitmap(disk::NUM_SECTORS);
+            let directory = directory::init_directory(num_dir_entries);
+
+            free_map.mark(FREE_MAP_SECTOR);
+            free_map.mark(DIRECTORY_SECTOR);
+
+            let map_header = filehdr::allocate(&free_map, FREE_MAP_SECTOR);
+            let dir_header = filehdr::allocate(&free_map, directory_file_size);
+
+            dir_header.set_dir();
+
+            map_header.write_back(FREE_MAP_SECTOR);
+            dir_header.write_back(DIRECTORY_SECTOR);
+
+            let free_map_file = openfile::init_open_file(FREE_MAP_SECTOR);
+            let directory_file = openfile::init_open_file(DIRECTORY_SECTOR);
+
+            free_map.write_back(free_map_file);
+            directory.write_back(directory_file);
+
+            Filesys {
+                free_map_file,
+                directory_file
+            }
+        } else {
+            Filesys {
+                free_map_file : openfile::init_open_file(FREE_MAP_SECTOR),
+                directory_file : openfile::init_open_file(DIRECTORY_SECTOR)
+            }
+        }
+    }
+
+    /// create a file in the Nachos file system (similar to UNIX create).
+    /// Since we can't increase the size of files dynamically, we have
+    /// to give Create the initial size of the file.
+    //
+    /// The steps to create a file are:
+    /// Make sure the file doesn't already exist
+    /// Allocate a sector for the file header
+    /// Allocate space on disk for the data blocks for the file
+    /// Add the name to the directory
+    /// Store the new file header on disk 
+    /// Flush the changes to the bitmap and the directory back to disk
+    ///
+    ///	Create fails if:
+    /// 	file is already in directory
+    ///	 	no free space for file header
+    ///	 	no free entry for file in directory
+    ///	 	no free space for data blocks for the file 
+    ///
+    ///	Note that this implementation assumes there is no concurrent access
+    ///	to the file system!
+    /// 
+    /// ### parameters
+    ///
+    ///	-**name** is the name of file to be created (NOT MODIFIED)
+    ///	-**initialSize** is the size of file to be created
+    ///	\return NO_ERROR if everything goes ok, otherwise, return an error
+    //              code as define in msgerror.h
+    pub fn create(name : String, initial_size : i32) -> i32 {
+
+    }
 }
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