computer science final

Consider the same circuit, consisting of an AND gate (at the top) and an OR gate (at the bottom). If the inputs to this circuit are A=1, B=0 and C=0, what would be the output of this circuit. Recall, 1 signifies current on the wire, whereas 0 signifies no current.

0

Consider the following circuit, consisting of an AND gate (at the top) and an OR gate (at the bottom). If the inputs to this circuit are A=1, B=1 and C=0, what would be the output of this circuit. Recall, 1 signifies current on the wire, whereas 0 signifies no current.

1

computer science themes

1. hardware: the physical components of computers 2. software: programs that execute on computers 3. theory: understanding the capabilities and limitations of computers

Transmission Control Protocol (TCP) and Internet Protocol (IP)

1. on the sender's computer: -TCP software breaks the message into packets and labels them by number -IP software labels the packets with source and destination addresses and controls packets' paths from sender to recipient 2. the packets travel independently across the internet, guided by routers accessing the IP packet labels 3. On the recipient's computer: -TCP software reassembles the packets using the number labels -if any packets are missing, requests are send to the sender (using IP packet labels)

advantages of packets

1. sending information in smaller units increases the efficient use of connections 2. transmitting packets independently allows the network to react to failures or network congestion 3. breaking the message into packets can improve reliability -since the packets are transmitted independently, it is likely that at least part of the message will arrive -software at the destination can recognize which packets are missing and request retransmission

packet switching

1. the message is broken into small packets, each labeled with a packet number 2. the packets travel independently across the network, perhaps arriving at the destination out of order 3. the packets are reassembled in the correct order to obtain the original message

Refer to the Newton.html page. How many successive approximations does Newton's algorithm require to compute the square root of 900?

11

What decimal value is represented by the binary number 1101 base 2.

13

Suppose you had a directory that listed each Creighton student (8,910 people), alphabetically by name. How many checks would be required to find a particular student, in the worst case, using binary search?

14

Consider Algorithm 1 for finding the oldest person in a room (which lines up the people and asks each person their birthday in order). If it takes 20 seconds to ask and write down a person's name and age, how long would it take to find the oldest person in a room of 10 people?

200 seconds

subfields of computer science

4 highly visible subfields: 1. algorithms and data structures 2. architecture 3. software engineering 4. artificial intelligence and robotics

Suppose that you have been given an O(N) algorithm that processes student grades, where N is the number of grades. If it takes 1 minute to process 1,000 grades using the algorithm, how long would you expect it to take to process 4,000 grades?

4 minutes

A byte, which consists of 8 bits, can represent 256 (2^8) different values. How many different values can two bytes (16 bits) represent?

65,536

A grayscale image is one in which each pixel can be white, or black, or various shades of gray in between. Assuming that there are 256 discernible shades of gray, how many bits would a bitmap require to represent a pixel in a grayscale image?

8

Consider Algorithm 2 for finding the oldest person in a room (which repeatedly has the people pair up, compare ages, and have the younger sit down). If it takes 20 seconds for a round (simultaneous pair comparisons), how long would it take to find the oldest person in a room of 10 people?

80

A microprocessor is a special-purpose computer that is used to control scientific machinery. True or False?

False

A sequence of instructions for assembling a bookcase does not qualify as an "algorithm", as the instructions are not written in formal, mathematical notation. True or False?

False

Commercial software systems are thoroughly tested so that all programming errors are identified and fixed before the system is marketed. True or False?

False

For a precise, clearly stated problem, there can only be one algorithm that provides a solution. True or False?

False

In most Web browsers, cookies are used to save local copies of downloaded pages and files in order to save time when they are accessed again. True or false?

False

In order to be classified as a "computer", a device must have a keyboard and display screen. True or false?

False

JPEG is a lossless format for representing images, since it loses no information when compressing the image content. True or False?

False

Moore's Law dictates that integrated circuitry must be manufactured out of silicon, as opposed to other semiconductors such as germanium. True or False?

False

The World Wide Web was developed in the early 1970s, shortly after the development of the Internet. True or false?

False

The steps of the scientific method are Decomposition, Pattern Recognition, Abstraction, and Algorithms. True or False?

False

Which of the following best describes the role of a domain name server?

It stores and distributes the IP addresses corresponding to domain names (e.g., www.creighton.edu)

Which of the following kinds of memory is volatile (i.e., requires a constant power supply to maintain its contents)?

RAM

Which of the following best describes the role of a Web crawler, or spider?

They traverse the Web, cataloging Web pages for use by Web searches engines.

A semiconductor is a metal that can be manipulated to be either a good or a bad conductor of electricity. True or False?

True

Ada Lovelace is generally acknowledged as the world's first programmer, because of her work on Babbage's Analytical Engine. True or False?

True

Digital sampling is the process of converting an analog sound wave into digital values. True or False?

True

Greek natural philosophy is often referred to as "pre-scientific", since it relied on contemplation and/or observations, but not experimentation. True or False?

True

In a centralized computer network, the failure of a single machine or connection can isolate large portions of the network. True or false?

True

Phishing is the act of obtaining sensitive information (e.g., credit card numbers, usernames, or passwords) by masquerading as a trusted entity in an email. True or False?

True

The "digital divide" refers to the fact that the disadvantaged in society (e.g., minorities, the poor, and uneducated citizens) are less likely to have access to the Internet. True or False?

True

The ARPANET, the precursor to today's Internet, was funded primarily by the U.S. Department of Defense. True or false?

True

The Turing Test was proposed by Alan Turing as a means of determining whether an artificially intelligent machine has been constructed. True or False?

True

The protocol that defines how Web browsers and servers communicate with each other is the HyperText Transfer Protocol (HTTP). True or false?

True

The three components that make up the von Neumann architecture are the CPU, memory and input/output devices. True or False?

True

The three recurring themes that define the discipline of computer science are hardware, software, and theory. True or False?

True

There are currently more devices connected to the Internet (of Things) than there are people in the world. True or false?

True

To produce the incredibly small and precise circuitry on microchips, hardware manufacturers use light-sensitive chemicals to etch circuitry into layers of semiconductor materials. True or False?

True

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. True or False?

True

Vacuum tubes, as they have no moving parts, enable the switching of electrical signals at speeds far exceeding those of relays. True or False?

True

When a Web page is loaded into a Web browser, JavaScript code in that page is executed by a JavaScript interpreter that is embedded in the browser. True or False?

True

cookies

a cookie is a small file that can be stored and accessed by a Web server similar to caching, browsers reserve space (a cookie folder) on the user's computer when the user visits a site, the Web server is allowed to store a small amount of data in a cookie file (e.g., date and time of visit, items purchased) when the user returns to that site, the Web server can retrieve any cookies it previously stored only the site that stored the cookie is able to retrieve it cookies can improve the user's experience, but can also be intrusive; most browsers enable the user to control the use of cookies

science

a system of knowledge covering general truths or the operation of general laws especially as obtained and tested through scientific method

output devices

allow the computer to display or broadcast its results examples: monitor, speaker, printer

input devices

allow the computer to receive data and instructions from external sources examples: keyboard, mouse, track pad, touch screen, microphone, scanner

high-level languages

allow the programmer to write code closer to the way humans think (as opposed to mimicking hardware operations) more natural, plus machine-independent the programmer is able to reason at a high-level of abstraction but programs must still be translated into machine language that the computer hardware can understand/execute

algorithm 2

allows you to perform multiple comparisons simultaneously the time needed to find the oldest person is proportional to the number of rounds it takes to shrink the line down to one person log base 2 (N) is the number of times N must be halved until it becomes 1 if you double the amount of people, the time needed to find the oldest person increases by the cost of one more comparison

analog

analog values represent data in a way that is analogous to real life allows for an infinite number of unique signals, but they are harder to reproduce good for storing data that is highly variable but does not need to be reproduced exactly

domain name servers (DNS)

are computers that store mappings between domain names and IP addresses domain names are hierarchical names for computers (e.g., bluejay.creighton.edu) they are much easier to remember and type than IP addresses domain name servers translate the names into their corresponding IP addresses

decomposition

breaking a large, complex problem into smaller, more manageable problems

Which of the following is NOT a task carried out by an operating system? a. control the CPU's operation, controlling how data and instructions are loaded from memory and accessed by the CPU b. manage the file system, organizing storage into files and directories c. control the circuitry of the CPU in order to execute program instructions d. provide a graphical user interface to make using the computer easier

c. control the circuitry of the CPU in order to execute program instructions

Which of the following would NOT provide evidence that information on the Web was reliable? a. the article has been edited or reviewed by other parties b. the author is well-known and respected in his/her field c. the author is funded by the industry that the article supports d. information cited in the article is relevant and timely

c. the author is funded by the industry that the article supports

computer science as a science

computer science is not a science in the same sense that biology and chemistry are computer science is the study of computation (more than just machinery) it involves all aspects of problem solving, including: 1. the design and analysis of algorithms 2. the formalization of algorithms as programs 3. the development of computational devices for executing programs 4. the theoretical study of the power and limitations of computing

World Wide Web

created in 1990 World Wide Web is software; consists of web pages, images, sound files, etc..., and the software that stores and retrieves those files the web couldn't exist without the internet; the internet is the hardware that stores and executes the web software

Which of the following statements about transmitting messages on the Internet is FALSE? a. Each computer on the Internet is assigned an IP address. b. The message is broken into packets using the Transmission Control Protocol (TCP). c. Packets are labeled with source and destination addresses using the Internet Protocol (IP). d. Each packet follows the same present path from the source computer to its destination. e. When the packets arrive at the destination, they are reassembled to yield the desired message.

d. Each packet follows the same present path from the source computer to its destination.

Which of the following claims about the Web is FALSE? a. Tim Berners-Lee invented the Web and developed the first Web browser and server software. b. A Web page is a text document that contains formatting information written in the Hypertext Markup Language (HTML) c. A Uniform Resource Locator (URL) specifies the address where a Web page can be found d. The most popular Web browser in the world today is Mozilla Firefox

d. the most popular Web browser in the world today is Mozilla Firefox

Hypertext Transfer Protocol (HTTP)

defines how messages between browsers and servers are formatted 1. when the user clicks on a link in the browser, the browser identifies the Web server, codes a page request in HTTP, and sends to the server to request the page 2. the server locates the page, adds its content to an HTTP response, and sends it to the browser for display the prefix http:// in a URL specifies that the HTTP protocol is to be used in communicating with the server the prefix https:// is similarly used for secure (encrypted) HTTP communications

digital

digital values utilize only a finite set of values limit the number of representable signals, but they are easily remembered and reproduced good for storing data when reproducibility is paramount when storing data on a computer, reproducibility of paramount because changing a single bit in a file can drastically change the data modern computers save and manipulate data as discrete (digital) values

The history of computers can be divided into generations based on advances in technology. Which of the following sequences correctly lists the technologies that defined generations 0 through 3 in chronological order?

electromagnetic relays --> vacuum tubes --> transistors --> integrated circuits

abstraction

focusing on important details while ignoring irrelevant information

caching

for efficiency reasons, browsers will sometimes cache pages/images the browser reserves a space (cache folder) on the user's computer to avoid redundant downloads, the browser will store a copy of a page/image in that reserved space (along with a time stamp) the next time the page/image is requested, it will first check the cache. If a copy is found, it sends a conditional request to the server. Essentially: "send this page/image only if it has been changed since the timestamp". If the server copy has not changed, the server sends back a brief acknowledgement message and the browser uses the cached copy. caching still requires the browser to contact the server, but only have to download the page if it has changed since last cached

electromagnetic relay

generation 0 is a physical switch which can be opened/closed via electrical current disadvantages: they jam and are slow

vacuum tubes

generation 1 is a light bulb containing a partial vacuum to speed electron flow Permit the electrons to move with minimal interference with the gas molecules. The electrons will fly across the bridges and fill the vacuum tube and complete the circuit. vacuum tubes could control the flow of electricity faster than relays since they had no moving parts replaced relays because they do not jam and are faster

transistors

generation 2 is a piece of silicon whose conductivity can be turned on and off using electric current they performed the same switching function of vacuum tubes, but were smaller, faster, more reliable, and cheaper to mass produce some historians claim the transistor was the most important invention of the 20th century

Integrated Circuits (IC)

generation 3 many transistors combined or wired on a small chip

microprocessors

generation 4 an integrated circuit silicon chip that contains the entire processing unit for a computer or a computerized appliance

ultra large scale integration (ULSI)

generation 5 the process of integrating millions of transistors on a single silicon semiconductor microchip

algorithm 1

involves asking each person's birthday and then comparing it to the birthday written on the page the amount of time to find the oldest person is proportional to the number of people if you double the amount of people, the time needed to find the oldest person will also double

binary search

involves continually cutting the desired search list in half until the item is found the algorithm is only applicable if the list is ordered by repeatedly cutting the potential range in half, binary search can hone in on the value very quickly is an O(log N) algorithm

consistency

is a measure of how close the results are each time you conduct the experiment

accuracy

is a measure of how close the results are to the correct (or expected) value

computational thinking

is a problem-solving approach that involves expressing problems and their solutions in ways that a computer could execute high-level characteristics of computational thinking are: 1. decomposition 2. pattern matching 3. abstraction 4. algorithms

algorithms

is a step-by-step sequence of instructions for carrying out some task use of algorithms is not limited to the domain of computing (recipes for baking cookies) in order for an algorithm to be effective, it must be stated in a manner that its intended executor can understand

sequential search

is an algorithm that involves examining each list item in sequential order until the desired item is found guarantees that you will find the item if it is in the list but it is not very practical for very large databases worst case: you may have to look at every entry in the list is a O(N) algorithm

bioinformatics

multi-disciplinary field that bridges the gap between biology and computer science focuses on using computers and computer science techniques to solve biological problems 1. computers are integrated with various scientific tools 2. computers are used to model biological systems 3. computers are used to store and process large amounts of biological data

natural sciences vs. computer science

natural sciences study naturally occurring phenomena and attempt to extract underlying laws of nature computer science studies human-made constructs: programs, computers, and computational modes

lossless format

no information is lost in the compression commonly used for precise pictures, such as line drawings reduces size by factor of 2-4 GIF (Graphics Interchange Format)

scientific method

provides the common process by which modern science is conducted 1. observe a phenomenon 2. hypothesize how it works 3. design an experiment to test it 4. conduct the experiment 5. analyze the results generally, the process repeats since the results may lead to revisions to the hypothesis or experiment

interpreter

reads one high-level statement at a time, immediately translating and executing the statement before processing the next one Javascript is an interpreted language advantage: the translation is immediate disadvantage: if you want to hear the speech again, must interpret all over again

pattern matching

recognizing how solutions to similar problems can be applied to new problems

distributed network

redundant connections provide alternate routes for messages, allowing them to circumvent failed machines or connections will provide a communication network that is resistant to attack or mechanical failure

hardware

refers to the physical components of a computer system (e.g., monitor, keyboard, mouse, hard drive)

software

refers to the programs that execute on the computer (e.g., word processing program, web browser)

O(log N) algorithm

requires time proportional to the logarithm of the problem size given an O(log N) algorithm, doubling the problem size adds a constant amount of work algorithm 2 is O(log N)

O(N) algorithm

requires time proportional to the size of problem given a O(N) algorithm, doubling the problem size doubles the work algorithm 1 is classified as O(N)

memory

stores information to be processed as well as programs (instructions specifying the steps necessary to complete specific tasks) modern computers store and process information as binary digits (bits) memory capacity is usually specified in bytes

architecture

subfield concerned with methods of organizing hardware components into efficient, reliable systems application: parallel processing (multiple processors can sometimes be utilized to share the computational load)

software engineering

subfield connected with creating effective software systems software demand continues to grow, placing pressure on programmers to produce at faster rates

artificial intelligence

subfield that attempts to make computers exhibit human-like characteristics (e.g., the ability to reason and think)

algorithms and data structures

subfield that involves developing, analyzing and implementing algorithms for solving problems application: encryption encryption is the process of encoding a message so that it is decipherable only by its intended recipient example: 1. your browser contacts a server at Amazon, requesting a transaction 2. Amazon generates public/private keys for that transaction and sends the public key to your browser 3. your browser encrypts the transaction data using the public key and sends the encrypted data to Amazon 4. Amazon decrypts the data using the private key, confirms the transaction and destroys the keys

Central Processing Unit (CPU)

the CPU is the "brains" of the computer, responsible for controlling its inner workings carries out the instructions to process information made of circuitry despite its small size, the CPU is the most complex part of a computer (CPU circuitry can have 100s of millions of individual components) the CPU works by repeatedly fetching a program instruction from memory and executing that instruction

lossy format

the compression is not fully reversible (but more efficient) commonly used for photographs reduces size by a factor of 10-20 JPEG (Joint Photographic Experts Group)

compiler

translates the entire high-level language program to its equivalent machine-language instructions advantage: once translated, it can be read over and over very quickly disadvantage: must wait for the entire speech to to translated

data science

utilizes concepts and methods from computer science, math, and statistics to predict outcomes and extract insights from collections of data supervised learning: learn to predict future outcomes based on past behaviors unsupervised learning: process data to discover patterns and extract insights

Von Neumann Architecture

virtually all modern computers have the same underlying structure named after computer pioneer, John von Neumann, who popularized the design in the early 1950's Identifies three essential components: 1. input/output devices 2. memory 3. central processing unit

web browser and server

when the user clicks on a link, the browser sends a request to the server for that page. The server locates the page and sends it to the browser for display.