[理工] OS交大100 第三大題 題組E.
題目如下：
Continue the previous questions. To reduce the memory space needed,
UNIX (Linux) uses permission bit to control users' access to files.
The permission bits 0755 with three classes of users are demonstrated
as follows:
RWX
a) owner access 7 => 111
b) group access 5 => 101
c) others access 5 => 101
Consider a system with ten domains and one hundred objects.
How many bits in total are needed for UNIX to maintain the permission
bits for all files? If the number of bits is P.
P = P4 * 5^4 + P3 * 5^3 + P2 * 5^2 + P1 * 5^1 + P0 (0≦P0,P1,P2,P3,P4＜5).
Please choose the correct values of P4, P3, P2, and P1
in the following.
37. P4=? (a)4, (b)3, (c)2, (d)1, (e)0
38. P3=? (a)4, (b)3, (c)2, (d)1, (e)0
39. P2=? (a)4, (b)3, (c)2, (d)1, (e)0
40 P1=? (a)4, (b)3, (c)2, (d)1, (e)0
交大公布正解為 37:D 38:C 39:D 40:E
因為補習時老師也沒有講過關於這類題目的計算，
所以看完題目完全沒有頭緒，
不知道如何計算，
不知道有沒有人會？感謝～
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