answer:
Mainframe computers are used by large companies and organisations to perform critical tasks that involve bulk data processing like transaction processing, census information, statistical data and so on. They consist of extensive input and output facilities, are very stable and dependable and handle millions of transactions every day
Explanation:
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Most email clients contain a "subject" that allows the user to read an email message without actually opening it.
Computer works on the Basis of multitasking.
Answer:
a) Speedup gain is 1.428 times.
b) Speedup gain is 1.81 times.
Explanation:
in order to calculate the speedup again of an application that has a 60 percent parallel component using Anklahls Law is speedup which state that:

Where S is the portion of the application that must be performed serially, and N is the number of processing cores.
(a) For N = 2 processing cores, and a 60%, then S = 40% or 0.4
Thus, the speedup is:

Speedup gain is 1.428 times.
(b) For N = 4 processing cores and a 60%, then S = 40% or 0.4
Thus, the speedup is:

Speedup gain is 1.81 times.