Re: [理工] [os]-政大97-資科

[crazyjoe (梨子)]

※ 引述《bigrat2 (MrEric)》之銘言：
: ※ 引述《b76516 (阿聰)》之銘言：
: : 剛好先前有鄉民問到同一題引用一下
:   我想請問 linked 的(2)(3)(4)
:   為什麼是22.22.40 呢？
:   謝謝大家的指教
: : 4. Consider a file consisting of 40 blocks. Assume that the file control block
: : (and the index block, in case of indexed allocation) is already in memory.
: : Calculate how many disk I/O operations are required for contiguous, linked,
: : and indexed(single-level) allocation strategies, if, for one block, the
: : following conditions hold. In the contiguous allocation case, assume that
: : there is no room to grow in the beginning, but there is room to grow in the
: : end. Assume that the block information to be added is stored in memory.
: : (1)The block is added at the beginning.
: : (2)The block is added in the middle.
: : (3)The block is removed from the middle.
: : (4)The block is removed from the end.
: : 答案寫說
: :    contiguous  linked  indexed
: : (1)   81          1       1
: : (2)   41          22      1
: : (3)   38          22      0
: : (4)   0           40      0
linked的

(2)20(找到中間)+1(改第20個的pointer到added block)+1(寫入addes block)=22

(3)21(找被刪的下一個block)+1(把被刪的上一個block指向剛剛找個block)=22

(4)最後一個被刪，要把他的前一個block指向null，所以要找39+1(寫入)=40

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推 bigrat2:很清楚 謝謝指教
推 polomoss:如果是link的added in the end??
推 bernachom:請教一下，那第一個呢??Y
推 bigrat2:add in the end 應該是3次 寫入block 改40的指標 改block
→ bigrat2:的指標到null  如果有錯誤請指教
推 polomoss:應該沒錯~我手上答案也是3