Why are some system interfaces implemented by dedicated system calls (to the kernel), and others
on top of message-based system calls?

What will be an ideal response?


Dedicated system calls are more efficient for simple calls than message-based calls (in which a system action
is initiated by sending a message to the kernel, involving message construction, dispatch etc.).
However, the advantage of implementing a system call as an RPC is that then a process can perform operations
transparently on either remote or local resources.

Computer Science & Information Technology

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Which of the following is equivalent to this code segment?

``` int total = 0; for (int i = 0; i <= 20; i += 2) { total += i; } ``` a. int total = 0; for (int i = 20; i < 0; i += 1) { total += i; } b. int total = 0; for (int i = 0; i <= 20; total += i, i += 2) {} c. int total = 0; for (int i = 0, i <= 20, total += i; i += 2) {} d. int total = 0; for (int i = 2; i < 20; total += i, i += 2) {}

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To perform a task for a given state of a MediaPlayer, you specify an object that imple- ments interface __________ (package java.lang).

What will be an ideal response?

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You can choose document type options in the Save As dialog box.

Answer the following statement true (T) or false (F)

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In this chapter we have described sequence numbers between a sender and receiver as a way to protect a communication stream against substitution and replay attacks. Describe a situation in which an attacker can substitute or replay in spite of sequence numbers. For which type of sequence numbering—one general stream of sequence numbers or a separate stream for each pair of communicators—is this attack effective?

What will be an ideal response?

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