--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/fs.h	Fri May 26 23:11:05 2017 +0900
@@ -0,0 +1,55 @@
+// On-disk file system format.
+// Both the kernel and user programs use this header file.
+
+// Block 0 is unused.
+// Block 1 is super block.
+// Blocks 2 through sb.ninodes/IPB hold inodes.
+// Then free bitmap blocks holding sb.size bits.
+// Then sb.nblocks data blocks.
+// Then sb.nlog log blocks.
+
+#define ROOTINO 1  // root i-number
+#define BSIZE 512  // block size
+
+// File system super block
+struct superblock {
+    uint    size;           // Size of file system image (blocks)
+    uint    nblocks;        // Number of data blocks
+    uint    ninodes;        // Number of inodes.
+    uint    nlog;           // Number of log blocks
+};
+
+#define NDIRECT 12
+#define NINDIRECT (BSIZE / sizeof(uint))
+#define MAXFILE (NDIRECT + NINDIRECT)
+
+// On-disk inode structure
+struct dinode {
+    short   type;           // File type
+    short   major;          // Major device number (T_DEV only)
+    short   minor;          // Minor device number (T_DEV only)
+    short   nlink;          // Number of links to inode in file system
+    uint    size;           // Size of file (bytes)
+    uint    addrs[NDIRECT+1]; // Data block addresses
+};
+
+// Inodes per block.
+#define IPB           (BSIZE / sizeof(struct dinode))
+
+// Block containing inode i
+#define IBLOCK(i)     ((i) / IPB + 2)
+
+// Bitmap bits per block
+#define BPB           (BSIZE*8)
+
+// Block containing bit for block b
+#define BBLOCK(b, ninodes) (b/BPB + (ninodes)/IPB + 3)
+
+// Directory is a file containing a sequence of dirent structures.
+#define DIRSIZ 14
+
+struct dirent {
+    ushort  inum;
+    char    name[DIRSIZ];
+};
+