Chapter 10


1. TRUE or FALSE? The discipline of computer science is solely concerned with the


design and development of computational machines.




2. TRUE or FALSE? Unlike in the natural sciences (such as physics and biology), the


systems that computer scientists investigate are largely artificial (e.g., programs,


computers, computation models).




3. TRUE or FALSE? The three recurring themes that define the discipline of computer


science are hardware, software, and theory.




4. TRUE or FALSE? Theoretical computer scientists have proven that any problem that can


be stated clearly is solvable via an algorithm.




5. TRUE or FALSE? Private-key encryption algorithms require the sender and recipient of


a message to agree upon a secret key (or password) for encoding and decoding the






6. TRUE or FALSE? In a time-sharing computer, the processor executes user programs in


sequence, completing the execution of one program before beginning the next one.




7. TRUE or FALSE? On an Ethernet network, computer A can send a message directly to


computer B, without any other computer on the network receiving that message.






8. TRUE or FALSE? When developing large software projects, it generally takes more


time to develop the code than it does to test and maintain it.




9. TRUE or FALSE? The Turing Test was proposed by Alan Turing as a means of


determining whether an artificially intelligent machine has been constructed.




10. TRUE or FALSE? According to the Code of Ethics proposed by the Association for


Computing Machinery (ACM), a computer professional is responsible for understanding


the potential impact of his or her work and for striving to minimize risks to the public.




11. Describe at least two similarities between computer science and natural sciences such as


physics, biology, and chemistry? Describe at least two differences.


Like the natural sciences, computer science is a field of study in which researchers


investigate problems that affect our daily lives. It is a rigorous approach to understanding


complex phenomena and solving problems, utilizing the scientific method of inquiry in


many applications. It is different from the natural sciences in that the systems computer


scientists investigate are largely artificial. Computer science is also a much newer field


of study, with greater interdisciplinary ties to mathematics and engineering.


12. Alan Turing is considered one of computer science’s founding fathers. Describe two of


his contributions to the discipline, and explain the importance of those contributions.


Turing designed an abstract computational machine, now known as a Turing machine,


which serves as a manageable tool for studying computation. Using this simple model of


computation (which is equivalent in power to today’s computers), Turing was able to


show that there exist problems whose solutions cannot be computed.


In the area of Artificial Intelligence, Turing predicted that computers might one day


exhibit intelligence, and proposed a test (now known as the Turing Test) by which


intelligence could be identified in machines.


13. Encrypt the message “Beware the Ides of March” using the Caesar encryption algorithm.


Recall that the Caesar algorithm encodes each individual letter by replacing it with the


letter three positions later in the alphabet.


Ehzduh wkh Lghv ri Pdufk




14. The following encoded text was created using Caesar’s encryption algorithm: “Brx jrw


lw”. Decode this message by performing the reverse translation, replacing each letter in


the code with the letter three positions earlier.


You got it


15. Using public-key encryption, the sender and recipient of a message do not need to agree


on a shared secret key before initiating secure communications. How is this possible?


That is, how can the sender, using publicly available information, encode a message that


can be decoded only by the intended recipient?


The idea behind public-key encryption is to assign each party a pair of associated keys,


one of which is public and the other private. A message encoded with a public key


requires the corresponding private key for decoding, and vice versa. Thus, if you know a


party’s public key, you can encode a message that only they can decode with their private


key, and without having to know their private key yourself.


16. Describe the fundamentals of parallel processing and explain how they are implemented


in Deep Blue, the first computer to defeat a world chess champion in a tournament




Parallel processing is an approach that employs multiple processors working in parallel to


share a computational load. One example is Deep Blue, the chess-playing computer


developed at IBM. Deep Blue contains 32 general-purpose processors and 512 specialpurpose


chess processors, each of which can work in parallel to evaluate potential chess


moves. Together, these processors can consider an average of 200 million possible chess


moves per second, and enabled Deep Blue to beat the world chess champion in 1996.


17. What does it mean for an operating system to support multitasking? How is multitasking


different from time sharing?


Multitasking is where a single user can have multiple programs executing


simultaneously. On a single processor computer, this is accomplished by the operating


system which quickly switches control of the CPU between programs. Time sharing is


similar to multitasking, except that the programs sharing the computer belong to different


users. In a sense, multiple users share the CPU via time sharing.


18. Describe one possible danger of accessing the Internet over a wireless connection, such


as WiFi or 3G. How can this danger be reduced?


Since WiFi and 3G are broadcast via radio waves, the signals could be intercepted by


anyone in the area. If sensitive information is being transmitted, e.g., credit card


numbers, these could be stolen. Utilizing encryption would protect the transmitted data.




19. Describe the individual steps that make up the software life cycle. What is the life cycle’s


significance in relation to the software engineering process?


While different software companies might use different tools or personnel management


policies, effective software engineering requires an overall development methodology


that addresses all aspects of the software life cycle. The steps in the software life cycle


are: requirement analysis and specification, design, implementation, testing, and


operation and maintenance.


20. Imagine that you are serving as the judge in a Turing Test. Describe the strategy you


would use to identify the computer. That is, what kinds of questions would you ask the


contestants, and how would the answers you received help you differentiate between the


computer and human?


Student responses will vary.


21. Describe three different ways in which computer technology is contributing to research in


the biological sciences.


1) Computers are integrated with laboratory tools and equipment, such as


microscope/computer hybrids.


2) Computers are used to model biological systems, such as drug interactions.


3) Computers are used to store and access large volumes of biological data, such as in


the human genome project.


22. Many diseases have genetic causes, which can be traced to mutations in a particular gene.


Visit the NCBI Web site ( and search through the online

resources to find two such diseases. Identify the diseases and the genetic mutations that


have been associated with those diseases.


asthma – chromosomes 5, 6, 11, 12, and 14


myotonic dystrophy – chromosome 19


23. Software piracy, the unauthorized copying of software without payment to the legal


owner, is a growing problem worldwide. Suppose that you are offered a chance to copy a


friend’s disk containing copyrighted software. What portions of the ACM Code of Ethics


would address this situation? According to the code, how should a computer professional


respond to such an offer?


This situation is covered by General Moral Imperative 1.5: Honor property rights


including copyrights and patent. Since the software is copyrighted and is someone else’s


intellectual property, you should not copy it.

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