GATE-CS-2015 (Set 1)

Question 61

Consider a uniprocessor system executing three tasks T1, T2 and T3, each of which is composed of an infinite sequence of jobs (or instances) which arrive periodically at intervals of 3, 7 and 20 milliseconds, respectively. The priority of each task is the inverse of its period and the available tasks are scheduled in order of priority, with the highest priority task scheduled first. Each instance of T1, T2 and T3 requires an execution time of 1, 2 and 4 milliseconds, respectively. Given that all tasks initially arrive at the beginning of the 1st milliseconds and task preemptions are allowed, the first instance of T3 completes its execution at the end of ______________ milliseconds.

• 5
• 10
• 12
• 15

Question 62

Consider the following pseudo code, where x and y are positive integers.

begin
   q := 0
   r := x
while r >= y do
   begin
      r := r – y
      q := q + 1
   end
end 

The post condition that needs to be satisfied after the program terminates is

• {r = qx + y ∧ r < y}
• {x = qy + r ∧ r < y}
• {y = qx + r ∧ 0 < r < y}
• { q + 1 < r–y ∧ y > 0}

Question 63

Suppose that everyone in a group of N people wants to communicate secretly with the N–1 others using symmetric key cryptographic system. The communication between any two persons should not be decodable by the others in the group. The number of keys required in the system as a whole to satisfy the confidentiality requirement is

• 2N
• N(N – 1)
• N(N – 1)/2
• (N – 1)²

Question 64

Select operation in SQL is equivalent to

• the selection operation in relational algebra
• the selection operation in relational algebra, except that select in SQL retains duplicates
• the projection operation in relational algebra
• the projection operation in relational algebra, except that select in SQL retains duplicates

Question 65

Which of the following options is the closest in meaning to the sentence below?

She enjoyed herself immensely at the party.

• She had a terrible time at the party
• She had a horrible time at the party
• She had a terrific time at the party
• She had a terrifying time at the party