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.
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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) {}
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?
You can choose document type options in the Save As dialog box.
Answer the following statement true (T) or false (F)
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?