diff --git a/src/fs-filo-vfs.adb b/src/fs-filo-vfs.adb
new file mode 100644
index 0000000..75df52b
--- /dev/null
+++ b/src/fs-filo-vfs.adb
@@ -0,0 +1,38 @@
+with Interfaces.C;
+with Interfaces.C.Strings;
+
+use Interfaces.C;
+
+package body FS.FILO.VFS is
+
+   function C_Mount return int
+   is
+      Success : Boolean;
+   begin
+      Mount (Success);
+      return (if Success then 1 else 0);
+   end C_Mount;
+
+   function C_Open (File_Path : Strings.chars_ptr) return int
+   is
+      Success : Boolean;
+   begin
+      Open (Strings.Value (File_Path), Success);
+      return (if Success then 1 else 0);
+   end C_Open;
+   
+   function C_Read (Buf : System.Address; Len : int) return int
+   is
+      subtype Buffer_Range is Natural range 0 .. Integer (Len) - 1;
+      Buffer : Buffer_Type (Buffer_Range)
+      with
+         Convention => C,
+         Address => Buf;
+
+      Read_Len : Natural;
+   begin
+      Read (Buffer, Read_Len);
+      return int (Read_Len);
+   end C_Read;
+
+end FS.FILO.VFS;
diff --git a/src/fs-filo-vfs.ads b/src/fs-filo-vfs.ads
index ce5da18..95fa71d 100644
--- a/src/fs-filo-vfs.ads
+++ b/src/fs-filo-vfs.ads
@@ -9,20 +9,21 @@
    with procedure Mount (Success : out Boolean);
 
    with procedure Open (File_Path : String; Success : out Boolean);
-   with procedure Close;
+   with procedure Close with Convention => C;
 
-   with procedure Read (Buf : out Buffer_Type; Success : out Boolean);
+   with procedure Read (Buf : out Buffer_Type; Len : out Natural);
 
 package FS.FILO.VFS
 with
-   SPARK_Mode => Off
+   SPARK_Mode => Off,
+   Convention => C
 is
 
-   function C_Mount return int is (0);
+   function C_Mount return int;
 
-   function C_Open (File_Path : Strings.chars_ptr) return int is (0);
-   procedure C_Close is null;
+   function C_Open (File_Path : Strings.chars_ptr) return int;
+   procedure C_Close renames Close;
    
-   function C_Read (Buf : System.Address; Len : int) return int is (0);
+   function C_Read (Buf : System.Address; Len : int) return int;
 
 end FS.FILO.VFS;