Directory entries
   position what
       0    little bits of information, like file type
       1    file's first block number
       2    file's length in characters
      3-7   name, up to 20 chars, padded with zeros at end if < 20

First block of a directory containing the following ordinary files in order of creation
   one.txt
         355 bytes long, occupying block 7
   two.b
         deleted but was 2001 bytes long, occupying blocks 8, 9, 10, 11
   threeabcdefghijklmnopqrstuvwxyz
         9876 bytes long, occupying blocks 12, 13, 14, ..., 28, 29, 20
   4
         1 byte long, occupying block 21
 
 0: 'F'
 1: 7
 2: 355
 3: 'one.'
 4: 'txt\0'
 5: '\0\0\0\0'
 6: '\0\0\0\0'
 7: '\0\0\0\0'
 8: 'X'
 9: 8
10: 2001
11: 'two.'
12: 'b\0\0\0'
13: '\0\0\0\0'
14: '\0\0\0\0'
15: '\0\0\0\0'
16: '\0\0\0\0'
17: 'F'
18: 12
19: 9876
20: 'thre'
21: 'eabc'
22: 'defg'
23: 'hijk'
24: 'lmno'
25: 'F'
26: 21
27: 1
28: '4\0\0\0'
29: '\0\0\0\0'
30: '\0\0\0\0'
31: '\0\0\0\0'
32: '\0\0\0\0'
33: '\0\0\0\0'
34: '\0\0\0\0'
35: '\0\0\0\0'
36: '\0\0\0\0'
37: '\0\0\0\0'
38: '\0\0\0\0'
39: '\0\0\0\0'
40: '\0\0\0\0'
41: '\0\0\0\0'
42: '\0\0\0\0'
43: '\0\0\0\0'
44: '\0\0\0\0'
45: '\0\0\0\0'
46: '\0\0\0\0'
47: '\0\0\0\0'
48: '\0\0\0\0'
49: '\0\0\0\0'
...
...
...
120: '\0\0\0\0'
121: '\0\0\0\0'
122: '\0\0\0\0'
123: '\0\0\0\0'
124: '\0\0\0\0'
125: '\0\0\0\0'
126: '\0\0\0\0'
127: '\0\0\0\0'