Which of the following statements is incorrect? An operating system provides an environment for the execution of programs. An operating system manages system resources. Operating systems provide both command line as well as graphical user interfaces. Operating systems must provide both protection and security.

Most shops require the technician to enter a starting and ending time on the repair order to track the actual time the vehicle was in the shop and closed out by the office. this time is referred to as _ time ? a. comeback b. ro c. cycle d. lead

Suppose there is a relation r(a, b, c) with a b+-tree index with search keys (a, b).1. what is the worst-case cost of finding records satisfying 10 < a < 50 using this index, in terms of the number of records n1, retrieved and the height h of the tree? 2. what is the worst-case cost of finding records satisfying 10 < a < 50 and 5 < b < 10 using this index, in terms of the number of records n2 that satisfy this selection, as well as n1 and h defined above? 3. under what conditions on n1 and n2, would the index be an efficient way of finding records satisfying the condition from part (2)?

Visualizing a game of “tag” to remember the meaning of contagious