[SP2005] 期中考第七題答案更正

[NeilPeng (閒閒沒事也會煩)]

同學你好，

期中考第七題寫 101th (100th) 或是 201th (200th) 都可以得到
完整的四分，如果你的答案是 201th (200th) 被扣分的，請帶著
你的考卷到 438 室找彭念劬助教更正。

我下午和晚上一般都會在實驗室，週二下課時也會到教室去，如有
不便之處還請見諒。

                                           SP2005 課程助教
                                                    彭念劬


答案更正原因如下：
===========================================================
If you write a program like the followings:

        fd = fopen("ascii.dat", "r");
        fn = fileno(fd);

        fgetc(fd);
        fseek(fd, 100, SEEK_SET);
        lseek(fn, 200, SEEK_SET);
        printf("%d\n", fgetc(fd));

You will get the 101th character.

However if you write a program like this:

        fd = fopen("ascii.dat", "r");
        fn = fileno(fd);

        fseek(fd, 100, SEEK_SET);
        lseek(fn, 200, SEEK_SET);
        printf("%d\n", fgetc(fd));

You will get the 201th character.

This is because the stream buffer of fd is totally empty
before the fseek() is invoked.

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※ 編輯: NeilPeng        來自: 140.113.23.113       (05/20 04:32)