These data values refer to the different types of blocks and items. They are used in many, many places in Minecraft. Block IDs are used to define blocks placed in the world and inventory items (including items in chests and items dropped in the world). Item IDs are only valid for items. Each inventory slot has a unique slot number. In a Beta world, Block data further defines blocks placed, describing for example the height of water or the direction a torch points. 
Icon  Dec  Hex  Block type  
 00  00  Air  
  01  01  Stone  
  02  02  Grass  
  03  03  Dirt  
  04  04  Cobblestone  
  05  05  Wooden Planks  
  06  06  Saplings D B  
  07  07  Bedrock  
  08  08  Water D  
  09  09  Stationary water D  
  10  0A  Lava D  
  11  0B  Stationary lava D  
  12  0C  Sand  
  13  0D  Gravel  
  14  0E  Gold Ore  
  15  0F  Iron Ore  
  16  10  Coal Ore  
  17  11  Wood D B  
  18  12  Leaves D B  
  19  13  Sponge  
  20  14  Glass  
  21  15  Lapis Lazuli Ore  
  22  16  Lapis Lazuli Block  
  23  17  Dispenser D T  
  24  18  Sandstone  
  25  19  Note Block T  
  26  1A  Bed D I  
  27  1B  Powered Rail D  
  28  1C  Detector Rail D  
  29  1D  Sticky Piston D  
  30  1E  Cobweb  
  31  1F  Tall Grass D  
Icon  Dec  Hex  Block type  
  32  20  Dead Bush  
  33  21  Piston D  
  34  22  Piston Extension D  
  35  23  Wool D B  
  36  24  Block moved by Piston T  
  37  25  Dandelion  
  38  26  Rose  
  39  27  Brown Mushroom  
  40  28  Red Mushroom  
  41  29  Block of Gold  
  42  2A  Block of Iron  
  43  2B  Double Slabs D B  
  44  2C  Slabs D B  
  45  2D  Bricks  
  46  2E  TNT  
  47  2F  Bookshelf  
  48  30  Moss Stone  
  49  31  Obsidian  
  50  32  Torch D  
  51  33  Fire D  
  52  34  Monster Spawner T  
  53  35  Wooden Stairs D  
  54  36  Chest D T  
  55  37  Redstone Wire D I  
  56  38  Diamond Ore  
  57  39  Block of Diamond  
  58  3A  Crafting Table  
  59  3B  Wheat Seeds D  
  60  3C  Farmland D  
  61  3D  Furnace D T  
  62  3E  Burning Furnace D T  
  63  3F  Sign Post D I T  
Icon  Dec  Hex  Block type  
  64  40  Wooden Door D I  
  65  41  Ladders D  
  66  42  Rails D  
  67  43  Cobblestone Stairs D  
  68  44  Wall Sign D T  
  69  45  Lever D  
  70  46  Stone Pressure Plate D  
  71  47  Iron Door D I  
  72  48  Wooden Pressure Plate D  
  73  49  Redstone Ore  
  74  4A  Glowing Redstone Ore  
  75  4B  Redstone Torch ("off" state) D  
  76  4C  Redstone Torch ("on" state) D  
  77  4D  Stone Button D  
  78  4E  Snow D  
  79  4F  Ice  
  80  50  Snow Block  
  81  51  Cactus D  
  82  52  Clay Block  
  83  53  Sugar Cane D I  
  84  54  Jukebox D T  
  85  55  Fence  
  86  56  Pumpkin D  
  87  57  Netherrack  
  88  58  Soul Sand  
  89  59  Glowstone Block  
  90  5A  Portal  
  91  5B  Jack-O-Lantern D  
  92  5C  Cake Block D I  
  93  5D  Redstone Repeater ("off" state) D I  
  94  5E  Redstone Repeater ("on" state) D I  
  95  5F  Locked Chest  
Icon  Dec  Hex  Block type  
  96  60  Trapdoor D  
  97  61  Hidden Silverfish D  
  98  62  Stone Bricks D B  
  99  63  Huge Brown Mushroom D  
  100  64  Huge Red Mushroom D  
  101  65  Iron Bars  
  102  66  Glass Pane  
  103  67  Melon  
  104  68  Pumpkin Stem D  
  105  69  Melon Stem D  
  106  6A  Vines D  
  107  6B  Fence Gate D  
  108  6C  Brick Stairs D  
  109  6D  Stone Brick Stairs D  
  110  6E  Mycelium  
  111  6F  Lily Pad  
  112  70  Nether Brick  
  113  71  Nether Brick Fence  
  114  72  Nether Brick Stairs D  
  115  73  Nether Wart D I  
  116  74  Enchantment Table T  
  117  75  Brewing Stand D T I  
  118  76  Cauldron D I  
  119  77  End Portal T  
  120  78  End Portal Frame D  
  121  79  End Stone  
  122  7A  Dragon Egg  
Item IDs All items have values above 255, making it easy to separate the Block IDs from the Item IDs. Entries marked with a D require additional data to fully define the item in a Beta world. The chainmail set is currently unobtainable in Survival mode without hacking or, in multiplayer, the /give server command. It is available in Creative mode, however. The same applies to all music discs except for 13 and cat. 

Icon  Dec  Hex  Item  
 256  100  Iron Shovel  
 257  101  Iron Pickaxe  
 258  102  Iron Axe  
 259  103  Flint and Steel  
 260  104  Red Apple  
 261  105  Bow  
 262  106  Arrow  
 263  107  Coal D  
 264  108  Diamond  
 265  109  Iron Ingot  
 266  10A  Gold Ingot  
 267  10B  Iron Sword  
 268  10C  Wooden Sword  
 269  10D  Wooden Shovel  
 270  10E  Wooden Pickaxe  
 271  10F  Wooden Axe  
 272  110  Stone Sword  
 273  111  Stone Shovel  
 274  112  Stone Pickaxe  
 275  113  Stone Axe  
 276  114  Diamond Sword  
 277  115  Diamond Shovel  
 278  116  Diamond Pickaxe  
 279  117  Diamond Axe  
 280  118  Stick  
 281  119  Bowl  
 282  11A  Mushroom Soup  
 283  11B  Gold Sword  
 284  11C  Gold Shovel  
 285  11D  Gold Pickaxe  
 286  11E  Gold Axe  
 287  11F  String  
Icon  Dec  Hex  Item  
 288  120  Feather  
 289  121  Gunpowder  
 290  122  Wooden Hoe  
 291  123  Stone Hoe  
 292  124  Iron Hoe  
 293  125  Diamond Hoe  
 294  126  Gold Hoe  
 295  127  Seeds  
 296  128  Wheat  
 297  129  Bread  
 298  12A  Leather Cap  
 299  12B  Leather Tunic  
 300  12C  Leather Pants  
 301  12D  Leather Boots  
 302  12E  Chain Helmet  
 303  12F  Chain Chestplate  
 304  130  Chain Leggings  
 305  131  Chain Boots  
 306  132  Iron Helmet  
 307  133  Iron Chestplate  
 308  134  Iron Leggings  
 309  135  Iron Boots  
 310  136  Diamond Helmet  
 311  137  Diamond Chestplate  
 312  138  Diamond Leggings  
 313  139  Diamond Boots  
 314  13A  Gold Helmet  
 315  13B  Gold Chestplate  
 316  13C  Gold Leggings  
 317  13D  Gold Boots  
 318  13E  Flint  
 319  13F  Raw Porkchop  
Icon  Dec  Hex  Item  
 320  140  Cooked Porkchop  
 321  141  Paintings  
 322  142  Golden Apple  
 323  143  Sign  
 324  144  Wooden door  
 325  145  Bucket  
 326  146  Water bucket  
 327  147  Lava bucket  
 328  148  Minecart  
 329  149  Saddle  
 330  14A  Iron door  
 331  14B  Redstone  
 332  14C  Snowball  
 333  14D  Boat  
 334  14E  Leather  
 335  14F  Milk  
 336  150  Clay Brick  
 337  151  Clay  
 338  152  Sugar Cane  
 339  153  Paper  
 340  154  Book  
 341  155  Slimeball  
 342  156  Minecart with Chest  
 343  157  Minecart with Furnace  
 344  158  Egg  
 345  159  Compass  
 346  15A  Fishing Rod  
 347  15B  Clock  
 348  15C  Glowstone Dust  
 349  15D  Raw Fish  
 350  15E  Cooked Fish  
 351  15F  Dye D  
Icon  Dec  Hex  Item  
 352  160  Bone  
 353  161  Sugar  
 354  162  Cake  
 355  163  Bed  
 356  164  Redstone Repeater  
 357  165  Cookie  
 358  166  Map  
 359  167  Shears  
 360  168  Melon Slice  
 361  169  Pumpkin Seeds  
 362  16A  Melon Seeds  
 363  16B  Raw Beef  
 364  16C  Steak  
 365  16D  Raw Chicken  
 366  16E  Cooked Chicken  
 367  16F  Rotten Flesh  
 368  170  Ender Pearl  
 369  171  Blaze Rod  
 370  172  Ghast Tear  
 371  173  Gold Nugget  
 372  174  Nether Wart  
 373  175  Potions D  
 374  176  Glass Bottle  
 375  177  Spider Eye  
 376  178  Fermented Spider Eye  
 377  179  Blaze Powder  
 378  17A  Magma Cream  
 379  17B  Brewing Stand  
 380  17C  Cauldron  
 381  17D  Eye of Ender  
 382  17E  Glistering Melon  
 383  17F  Spawner Egg D  
Icon  Dec  Hex  Item  
 2256  8D0  13 Disc  
 2257  8D1  Cat Disc  
 2258  8D2  blocks Disc  
 2259  8D3  chirp Disc  
 2260  8D4  far Disc  
 2261  8D5  mall Disc  
 2262  8D6  mellohi Disc  
 2263  8D7  stal Disc  
 2264  8D8  strad Disc  
 2265  8D9  ward Disc  
 2266  8DA  11 Disc  
Entity IDs Icon  Dec  Hex  Entity  
Drops  
 1  01  Dropped item  
 2  02  Experience Orb  
Projectiles  
 10  0A  Shot arrow  
 11  0B  Thrown snowball  
 12  0C  Ghast fireball  
 13  0D  Blaze fireball  
 14  0E  Thrown Ender Pearl  
 15  0F  Thrown Eye of Ender  
Blocks  
 20  14  Primed TNT  
 21  15  Falling block (gravel, sand)  
Vehicles  
 40  28  Minecart  
 41  29  Boat  
Icon  Dec  Hex  Entity  
Hostile mobs  
 50  32  Creeper  
 51  33  Skeleton  
 52  34  Spider  
 53  35  Giant  
 54  36  Zombie  
 55  37  Slime  
 56  38  Ghast  
 57  39  Zombie Pigman  
 58  3A  Enderman  
 59  3B  Cave Spider  
 60  3C  Silverfish  
 61  3D  Blaze  
 62  3E  Magma Cube  
 63  3F  Enderdragon  
Icon  Dec  Hex  Entity  
Passive mobs  
 90  5A  Pig  
 91  5B  Sheep  
 92  5C  Cow  
 93  5D  Chicken  
 94  5E  Squid  
 95  5F  Wolf  
 96  60  Mooshroom  
 97  61  Snow Golem  
NPCs  
 120  78  Villager  
Other  
 200  C8  Ender Crystal  
Icon  Dec  Hex  Block type  
 00  00  Air  
  01  01  Stone  
  02  02  Grass  
  03  03  Dirt  
  04  04  Cobblestone  
  05  05  Wooden Planks  
  06  06  Saplings D B  
  07  07  Bedrock  
  08  08  Water D  
  09  09  Stationary water D  
  10  0A  Lava D  
  11  0B  Stationary lava D  
  12  0C  Sand  
  13  0D  Gravel  
  14  0E  Gold Ore  
  15  0F  Iron Ore  
  16  10  Coal Ore  
  17  11  Wood D B  
  18  12  Leaves D B  
  19  13  Sponge  
  20  14  Glass  
  21  15  Lapis Lazuli Ore  
  22  16  Lapis Lazuli Block  
  23  17  Dispenser D T  
  24  18  Sandstone  
  25  19  Note Block T  
  26  1A  Bed D I  
  27  1B  Powered Rail D  
  28  1C  Detector Rail D  
  29  1D  Sticky Piston D  
  30  1E  Cobweb  
  31  1F  Tall Grass D  
Icon  Dec  Hex  Block type  
  32  20  Dead Bush  
  33  21  Piston D  
  34  22  Piston Extension D  
  35  23  Wool D B  
  36  24  Block moved by Piston T  
  37  25  Dandelion  
  38  26  Rose  
  39  27  Brown Mushroom  
  40  28  Red Mushroom  
  41  29  Block of Gold  
  42  2A  Block of Iron  
  43  2B  Double Slabs D B  
  44  2C  Slabs D B  
  45  2D  Bricks  
  46  2E  TNT  
  47  2F  Bookshelf  
  48  30  Moss Stone  
  49  31  Obsidian  
  50  32  Torch D  
  51  33  Fire D  
  52  34  Monster Spawner T  
  53  35  Wooden Stairs D  
  54  36  Chest D T  
  55  37  Redstone Wire D I  
  56  38  Diamond Ore  
  57  39  Block of Diamond  
  58  3A  Crafting Table  
  59  3B  Wheat Seeds D  
  60  3C  Farmland D  
  61  3D  Furnace D T  
  62  3E  Burning Furnace D T  
  63  3F  Sign Post D I T  
Icon  Dec  Hex  Block type  
  64  40  Wooden Door D I  
  65  41  Ladders D  
  66  42  Rails D  
  67  43  Cobblestone Stairs D  
  68  44  Wall Sign D T  
  69  45  Lever D  
  70  46  Stone Pressure Plate D  
  71  47  Iron Door D I  
  72  48  Wooden Pressure Plate D  
  73  49  Redstone Ore  
  74  4A  Glowing Redstone Ore  
  75  4B  Redstone Torch ("off" state) D  
  76  4C  Redstone Torch ("on" state) D  
  77  4D  Stone Button D  
  78  4E  Snow D  
  79  4F  Ice  
  80  50  Snow Block  
  81  51  Cactus D  
  82  52  Clay Block  
  83  53  Sugar Cane D I  
  84  54  Jukebox D T  
  85  55  Fence  
  86  56  Pumpkin D  
  87  57  Netherrack  
  88  58  Soul Sand  
  89  59  Glowstone Block  
  90  5A  Portal  
  91  5B  Jack-O-Lantern D  
  92  5C  Cake Block D I  
  93  5D  Redstone Repeater ("off" state) D I  
  94  5E  Redstone Repeater ("on" state) D I  
  95  5F  Locked Chest  
Icon  Dec  Hex  Block type  
  96  60  Trapdoor D  
  97  61  Hidden Silverfish D  
  98  62  Stone Bricks D B  
  99  63  Huge Brown Mushroom D  
  100  64  Huge Red Mushroom D  
  101  65  Iron Bars  
  102  66  Glass Pane  
  103  67  Melon  
  104  68  Pumpkin Stem D  
  105  69  Melon Stem D  
  106  6A  Vines D  
  107  6B  Fence Gate D  
  108  6C  Brick Stairs D  
  109  6D  Stone Brick Stairs D  
  110  6E  Mycelium  
  111  6F  Lily Pad  
  112  70  Nether Brick  
  113  71  Nether Brick Fence  
  114  72  Nether Brick Stairs D  
  115  73  Nether Wart D I  
  116  74  Enchantment Table T  
  117  75  Brewing Stand D T I  
  118  76  Cauldron D I  
  119  77  End Portal T  
  120  78  End Portal Frame D  
  121  79  End Stone  
  122  7A  Dragon Egg  
Item IDs All items have values above 255, making it easy to separate the Block IDs from the Item IDs. Entries marked with a D require additional data to fully define the item in a Beta world. The chainmail set is currently unobtainable in Survival mode without hacking or, in multiplayer, the /give server command. It is available in Creative mode, however. The same applies to all music discs except for 13 and cat. 

Icon  Dec  Hex  Item  
 256  100  Iron Shovel  
 257  101  Iron Pickaxe  
 258  102  Iron Axe  
 259  103  Flint and Steel  
 260  104  Red Apple  
 261  105  Bow  
 262  106  Arrow  
 263  107  Coal D  
 264  108  Diamond  
 265  109  Iron Ingot  
 266  10A  Gold Ingot  
 267  10B  Iron Sword  
 268  10C  Wooden Sword  
 269  10D  Wooden Shovel  
 270  10E  Wooden Pickaxe  
 271  10F  Wooden Axe  
 272  110  Stone Sword  
 273  111  Stone Shovel  
 274  112  Stone Pickaxe  
 275  113  Stone Axe  
 276  114  Diamond Sword  
 277  115  Diamond Shovel  
 278  116  Diamond Pickaxe  
 279  117  Diamond Axe  
 280  118  Stick  
 281  119  Bowl  
 282  11A  Mushroom Soup  
 283  11B  Gold Sword  
 284  11C  Gold Shovel  
 285  11D  Gold Pickaxe  
 286  11E  Gold Axe  
 287  11F  String  
Icon  Dec  Hex  Item  
 288  120  Feather  
 289  121  Gunpowder  
 290  122  Wooden Hoe  
 291  123  Stone Hoe  
 292  124  Iron Hoe  
 293  125  Diamond Hoe  
 294  126  Gold Hoe  
 295  127  Seeds  
 296  128  Wheat  
 297  129  Bread  
 298  12A  Leather Cap  
 299  12B  Leather Tunic  
 300  12C  Leather Pants  
 301  12D  Leather Boots  
 302  12E  Chain Helmet  
 303  12F  Chain Chestplate  
 304  130  Chain Leggings  
 305  131  Chain Boots  
 306  132  Iron Helmet  
 307  133  Iron Chestplate  
 308  134  Iron Leggings  
 309  135  Iron Boots  
 310  136  Diamond Helmet  
 311  137  Diamond Chestplate  
 312  138  Diamond Leggings  
 313  139  Diamond Boots  
 314  13A  Gold Helmet  
 315  13B  Gold Chestplate  
 316  13C  Gold Leggings  
 317  13D  Gold Boots  
 318  13E  Flint  
 319  13F  Raw Porkchop  
Icon  Dec  Hex  Item  
 320  140  Cooked Porkchop  
 321  141  Paintings  
 322  142  Golden Apple  
 323  143  Sign  
 324  144  Wooden door  
 325  145  Bucket  
 326  146  Water bucket  
 327  147  Lava bucket  
 328  148  Minecart  
 329  149  Saddle  
 330  14A  Iron door  
 331  14B  Redstone  
 332  14C  Snowball  
 333  14D  Boat  
 334  14E  Leather  
 335  14F  Milk  
 336  150  Clay Brick  
 337  151  Clay  
 338  152  Sugar Cane  
 339  153  Paper  
 340  154  Book  
 341  155  Slimeball  
 342  156  Minecart with Chest  
 343  157  Minecart with Furnace  
 344  158  Egg  
 345  159  Compass  
 346  15A  Fishing Rod  
 347  15B  Clock  
 348  15C  Glowstone Dust  
 349  15D  Raw Fish  
 350  15E  Cooked Fish  
 351  15F  Dye D  
Icon  Dec  Hex  Item  
 352  160  Bone  
 353  161  Sugar  
 354  162  Cake  
 355  163  Bed  
 356  164  Redstone Repeater  
 357  165  Cookie  
 358  166  Map  
 359  167  Shears  
 360  168  Melon Slice  
 361  169  Pumpkin Seeds  
 362  16A  Melon Seeds  
 363  16B  Raw Beef  
 364  16C  Steak  
 365  16D  Raw Chicken  
 366  16E  Cooked Chicken  
 367  16F  Rotten Flesh  
 368  170  Ender Pearl  
 369  171  Blaze Rod  
 370  172  Ghast Tear  
 371  173  Gold Nugget  
 372  174  Nether Wart  
 373  175  Potions D  
 374  176  Glass Bottle  
 375  177  Spider Eye  
 376  178  Fermented Spider Eye  
 377  179  Blaze Powder  
 378  17A  Magma Cream  
 379  17B  Brewing Stand  
 380  17C  Cauldron  
 381  17D  Eye of Ender  
 382  17E  Glistering Melon  
 383  17F  Spawner Egg D  
Icon  Dec  Hex  Item  
 2256  8D0  13 Disc  
 2257  8D1  Cat Disc  
 2258  8D2  blocks Disc  
 2259  8D3  chirp Disc  
 2260  8D4  far Disc  
 2261  8D5  mall Disc  
 2262  8D6  mellohi Disc  
 2263  8D7  stal Disc  
 2264  8D8  strad Disc  
 2265  8D9  ward Disc  
 2266  8DA  11 Disc  
Entity IDs Icon  Dec  Hex  Entity  
Drops  
 1  01  Dropped item  
 2  02  Experience Orb  
Projectiles  
 10  0A  Shot arrow  
 11  0B  Thrown snowball  
 12  0C  Ghast fireball  
 13  0D  Blaze fireball  
 14  0E  Thrown Ender Pearl  
 15  0F  Thrown Eye of Ender  
Blocks  
 20  14  Primed TNT  
 21  15  Falling block (gravel, sand)  
Vehicles  
 40  28  Minecart  
 41  29  Boat  
Icon  Dec  Hex  Entity  
Hostile mobs  
 50  32  Creeper  
 51  33  Skeleton  
 52  34  Spider  
 53  35  Giant  
 54  36  Zombie  
 55  37  Slime  
 56  38  Ghast  
 57  39  Zombie Pigman  
 58  3A  Enderman  
 59  3B  Cave Spider  
 60  3C  Silverfish  
 61  3D  Blaze  
 62  3E  Magma Cube  
 63  3F  Enderdragon  
Icon  Dec  Hex  Entity  
Passive mobs  
 90  5A  Pig  
 91  5B  Sheep  
 92  5C  Cow  
 93  5D  Chicken  
 94  5E  Squid  
 95  5F  Wolf  
 96  60  Mooshroom  
 97  61  Snow Golem  
NPCs  
 120  78  Villager  
Other  
 200  C8  Ender Crystal  
0x2: Facing West 
0x3: Facing South 
0x4: Facing North 
Ground levers: 

0x5: Lever points South when off. 
0x6: Lever points East when off. (Note that unlike the other types of switch, this version didn't power wires around the block it was sitting on. This bug was fixed in Beta 1.6) 
Doors The two least significant bits are the orientation of the door, that is, the corner in which its hinge is positioned: 

0x0: Northwest corner 
0x1: Northeast corner 
0x2: Southeast corner 
0x3: Southwest corner 
The two bits above are flags: 

0x8: If this bit is set, this is the top half of a door (else the lower half). 
0x4: If this bit is set, the door has swung counterclockwise around its hinge. 
For example, the bottom half of a door with its hinge on the Southwest corner, which is swung so that it is closed when viewed from the West, will have a data value of (3 | 4) = (3 + 4) = 7. 

Buttons 0x8 If this bit is set, the button has been pressed. If this bit is set in a saved level, the button will remain pressed for an undefined length of time after the level is loaded. 
Button direction: 

0x1: Facing East 
0x2: Facing West 
0x3: Facing South 
0x4: Facing North 
Sign Posts 0x0: South 
0x1: South-Southwest 
0x2: Southwest 
0x3: West-Southwest 
0x4: West 
0x5: West-Northwest 
0x6: Northwest 
0x7: North-Northwest 
0x8: North 
0x9: North-Northeast 
0xA: Northeast 
0xB: East-Northeast 
0xC: East 
0xD: East-Southeast 
0xE: Southeast 
0xF: South-Southeast 
Wall Signs, Furnaces, Dispensers and Chests 0x2: Facing North 
0x3: Facing South 
0x4: Facing West 
0x5: Facing East 
Pumpkins and Jack-O-Lanterns 0x0: Facing South 
0x1: Facing West 
0x2: Facing North 
0x3: Facing East 
Pressure Plates 0x1: If this bit is set, the plate is pressed. 
Slab and Double Slab material Icon  Value  Description  
 0x0  Stone Slab  
 0x1  Sandstone Slab  
 0x2  Wooden Slab  
 0x3  Cobblestone Slab  
 0x4  Brick Slab  
 0x5  Stone Brick Slab  
 0x6  Stone Slab  
Snow  
Heights of snow from 0-7, going from left to right0x0: Normal snowfall height 
... 
0x7: Full block size height 
The height repeats for values 8-15. Note that snow does not occur naturally at other heights than 0, but can be edited or hacked in. Values 0-2 has no hitbox, values 3-7 has the same hitbox as a slab. 

Cake 0x0: 0 pieces eaten 
0x1: 1 piece eaten 
0x2: 2 pieces eaten 
0x3: 3 pieces eaten 
0x4: 4 pieces eaten 
0x5: 5 pieces eaten 
Beds 0x0: Head is pointing South 
0x1: Head is pointing West 
0x2: Head is pointing North 
0x3: Head is pointing East 
0x4: (bit flag) - When 0, the bed is empty. When 1, the bed is occupied. 
0x8: (bit flag) - When 0, the foot of the bed. When 1, the head of the bed. 
Redstone Repeater Low (1st & 2nd) bits: 

0x0: Facing North 
0x1: Facing East 
0x2: Facing South 
0x3: Facing West 
High (3rd & 4th) bits: 

0x0: 1 tick delay 
0x1: 2 tick delay 
0x2: 3 tick delay 
0x3: 4 tick delay 
Redstone Wire 0xF is a wire placed right next to a power source (like a redstone torch). The value declines with distance until 0x0, which is a non-powered wire. The direction of the wire is not saved but calculated at runtime. 

Tall Grass Icon  Value  Description  
 0x0  Dead shrub (identical in appearance to block Dead Bush when placed, but acts like Tall Grass)  
 0x1  Tall grass  
 0x2  Fern  
Trapdoors 0x4 is a bit that determines whether or not the trapdoor is swung open. 0 for closed (on the ground), 1 for open (against its connecting wall). The remaining two bits describe which wall the trapdoor is attached to: 

0x0: Attached to the South wall 
0x1: Attached to the North wall 
0x2: Attached to the East wall 
0x3: Attached to the West wall 
Piston The top bit (0x8) is a status bit that determines whether the piston is pushed out or not. 1 for pushed out, 0 for retracted. 

The bottom three bits are a value from 0 to 5, indicating the direction of the piston (the direction the piston head is pointing) 

0: Down 
1: Up 
2: North 
3: South 
4: West 
5: East 
Piston Extension The top bit (0x8) is a status bit that determines whether the head is sticky or not (note that the Piston Body actually has completely different block types for Sticky and Regular). 1 is sticky, 0 is regular. 

The bottom three bits are a value from 0 to 5, indicating the direction of the piston (the direction the piston head is pointing). 

0: Down 
1: Up 
2: North 
3: South 
4: West 
5: East 
Stone Brick 0: Normal 
1: Mossy 
2: Cracked 
Huge brown and red mushroom Huge mushrooms consist of the same blocks throughout their structure, the data value of each block decides the texture. The default texture on all sides is porous flesh. The cap texture can be either the brown mushroom or red mushroom texture, the textures for porous and stem sides are identical. 

Value  Description  Textures  
0  Fleshy piece  Pores on all sides  
1  Corner piece  Cap texture on top, West and North  
2  Side piece  Cap texture on top and North  
3  Corner piece  Cap texture on top, North and East  
4  Side piece  Cap texture on top and West  
5  Top piece  Cap texture on top  
6  Side piece  Cap texture on top and East  
7  Corner piece  Cap texture on top, South and West  
8  Side piece  Cap texture on top and South  
9  Corner piece  Cap texture on top, East and South  
10  Stem piece  Stem texture on all four sides, pores on top and bottom  
Vines Determines the face against which the vine is anchored. Note that (except for Top) these are testable as bit flags, unlike most of the other directional data for other block types. Multiple sides can contain vines. The "top" attachment is assumed to be present if data is 0 or there is solid block above. 

1: South 
2: West 
4: North 
8: East 
Fence Gates 0x4 is a bit flag: 1 is open, 0 is closed. The remaining two bits determine in which direction the gate will open. 

0: To the South 
1: To the West 
2: To the North 
3: To the East 
Hidden Silverfish A silverfish will hide inside a Stone, Cobblestone, or Stone Brick block, changing it into a Hidden Silverfish block. The data value tells us its appearance: 

0: Stone 
1: Cobblestone 
2: Stone Brick 
Potions A Glass Bottle filled with a potion. Potion type is stored in item's damage value as a 16-bit number. Potion effect, name, and other flags are encoded on bits. Effect duration itself isn't there, but can be calculated from other values. 

Current meaning of bits is described below. Note that potion name overlaps with potion effect and tier. 

Bit  Dec  Hex  Meaning  
0  1  0001  Potion effect  Potion name  
1  2  0002  
2  4  0004  
3  8  0008  
4  16  0010  
5  32  0020  Tier  
6  64  0040  Extended duration  
7  128  0800  (ignored)  
8  256  0100  
9  512  0200  
10  1024  0400  
11  2048  0800  
12  4096  1000  
13  8192  2000  
14  16384  4000  Splash potion  
15  32768  8000  (ignored)  

To calculate damage value of potion with desired effect use the following formula: 

DV = potion_effect + tier_bit + extended_bit + splash_bit
for example: 

potion with "Instant Health" effect has damage value 5 (= 5 + 0 + 0 + 0); 
potion with extended "Slowness" effect has value 74 (= 10 + 0 + 64 + 0); 
splash potion with tier II "Strength" effect has value 16425 (= 9 + 32 + 0 + 16384). 
To get potion with certain name, use the following formula: 

DV = potion_name + extended_bit + splash_bit
for example: 

"Splash Charming Potion" has damage value 16422 (= 38 + 0 + 16384) 
"Potion name" bits Dec  Hex  Potion  
0  00  Water Bottle / Mundane Potion  
1  01  Potion of Regeneration  
2  02  Potion of Swiftness  
3  03  Potion of Fire Resistance  
4  04  Potion of Poison  
5  05  Potion of Healing  
6  06  Clear Potion  
7  07  Clear Potion  
8  08  Potion of Weakness  
9  09  Potion of Strength  
10  0a  Potion of Slowness  
11  0b  Diffuse Potion  
12  0c  Potion of Harming  
13  0d  Artless Potion  
14  0e  Thin Potion  
15  0f  Thin Potion  
Dec  Hex  Potion  
16  10  Awkward Potion  
17  11  Potion of Regeneration  
18  12  Potion of Swiftness  
19  13  Potion of Fire Resistance  
20  14  Potion of Poison  
21  15  Potion of Healing  
22  16  Bungling Potion  
23  17  Bungling Potion  
24  18  Potion of Weakness  
25  19  Potion of Strength  
26  1a  Potion of Slowness  
27  1b  Smooth Potion  
28  1c  Potion of Harming  
29  1d  Suave Potion  
30  1e  Debonair Potion  
31  1f  Debonair Potion  
Dec  Hex  Potion  
32  20  Thick Potion  
33  21  Potion of Regeneration II  
34  22  Potion of Swiftness II  
35  23  Potion of Fire Resistance  
36  24  Potion of Poison II  
37  25  Potion of Healing II  
38  26  Charming Potion  
39  27  Charming Potion  
40  28  Potion of Weakness  
41  29  Potion of Strength II  
42  2a  Potion of Slowness  
43  2b  Refined Potion  
44  2c  Potion of Harming II  
45  2d  Cordial Potion  
46  2e  Sparkling Potion  
47  2f  Sparkling Potion  
Dec  Hex  Potion  
48  30  Potent Potion  
49  31  Potion of Regeneration II  
50  32  Potion of Swiftness II  
51  33  Potion of Fire Resistance  
52  34  Potion of Poison II  
53  35  Potion of Healing II  
54  36  Rank Potion  
55  37  Rank Potion  
56  38  Potion of Weakness  
57  39  Potion of Strength II  
58  3a  Potion of Slowness  
59  3b  Acrid Potion  
60  3c  Potion of Harming II  
61  3d  Gross Potion  
62  3e  Stinky Potion  
63  3f  Stinky Potion  

Note: potion with name set to 0 is called "Water Bottle" only if no other bit is set. Otherwise, it is called "Mundane Potion". 

Note: potions with splash potion bit set have additional "Splash " prefix. 

"Potion effect" bits Dec  Hex  Effect  Duration  Bottles  Icon  Effect color  
0  0  -  -    -  
1  1  Regeneration  0:45     Pink  
2  2  Speed  3:00     Sky blue  
3  3  Fire Resistance  3:00     Orange  
4  4  Poison  0:45     Green  
5  5  Instant Health  instant    -  -  
6  6  -  -    -  -  
7  7  -  -    -  -  
8  8  Weakness  1:30     Grey  
9  9  Strength  3:00     Dark red  
10  a  Slowness  1:30     Blue-Grey  
11  b  -  -    -  -  
12  c  Instant Damage  instant    -  -  
13  d  -  -    -  -  
14  e  -  -    -  -  
15  f  -  -    -  -  
"Tier" bit Dex  Hex  Meaning  
0  0000  Tier I effect.  
32  0020  Tier II effect. Multiply duration by 1/2.  

Note: Fire Resistance, Weakness and Slowness effects have no second tier. Their strength and duration are unaffected by this bit. 

"Extended duration" bit Dex  Hex  Meaning  
0  0000  Base duration.  
64  0040  Multiply duration by 8/3.  
"Splash potion" bit Dex  Hex  Meaning  
0  0000  Drinkable potion.  
16384  4000  Splash potion. Multiply duration by 3/4.  
Brewing Stand The bottom three bits are bit flags for which bottle slots actually contain bottles. The actual bottle contents (and the reagent at the top) are stored in a TileEntity for this block, not in the data field. 

0x1: The slot pointing East 
0x2: The slot pointing Southwest 
0x4: The slot pointing Northwest 
Cauldron The data value stores the amount of water kept in the cauldron, in units of glass bottles that can be filled. 

0: Empty 
1: 1/3 filled 
2: 2/3 filled 
3: Fully filled 
End Portal Frame The bottom two bits determine which "side" of the whole portal frame this block is a part of. 

0x4 is a bit flag: 0 is an "empty" frame block, 1 is a block with an Eye of Ender inserted 

