computer science midterm chap 1-4

exponent

Double stars ** are used to calculate an

The while loop

Examples of loop applications Calculation compound interest Simulations, event driven programs Drawing tiles The loop executes instructions repeatedly while a condition is true

>

Greater than

>=

Greater than or equal

A library

a collection of code, written and compiled by someone else, that is ready for you to use in your program

Variables

a named storage location in a computer

Software

a sequence of instructions and decisions implemented in some language and translated to a form that can be executed or run on the computer.

Algorithm

a step by step description of how to solve a problem.

Constants

a variable whose value should not be changed after it's assigned initial value

Which of the following code snippets displays the output exactly 10 times? a. i = 0 while i < 10 : print("This is example 2.") i = i + 1 b. i = 0 while i < 10 : print("This is example 3.") c. i = 1 while i < 10 : print("This is example 4.") i = i + 1 d. i = 0 while i <= 10 : print("This is example 1.") i = i + 1

a. i = 0 while i < 10 : print("This is example 2.") i = i + 1

What is the output of the following code snippet? i = 1 while i <= 10 : print("Inside the while loop") i = i + 10 answers: a. "Inside the while loop" will be displayed only once. b. No output after successful compilation. c. "Inside the while loop" will be displayed 10 times. d. No output because of compilation error.

a. "Inside the while loop" will be displayed only once.

What will be printed by the statements below? val = 1 sum = 0 while val < 5 : sum = sum + val val = val + 1 print(sum) answers: a. 10 b. 4 c. 5 d. 15

a. 10

What is the value of the price variable after the following code snippet is executed? price = 42 if price < 40 : price = price + 10 if price > 30 : price = price * 2 if price < 100 : price = price - 20 answers: a. 64 b. 52 c. 84 d. 42

a. 64

What is the last output line of the code snippet given below? i = 0 j = 0 while i < 10 : num = 1 j = i while j > 1 : print(j, end = " ") num = num * 2 j = j - 1 print("***") i = i + 1 answers: a. 9 8 7 6 5 4 3 2 *** b. 2 *** c. 8 7 6 5 4 3 2 *** d. 3 2 ***

a. 9 8 7 6 5 4 3 2 ***

What value is displayed by the following code segment? name = "John Smith" print(name.startswith("john")) answers: a. False b. True c. -1 d. 0

a. False

Consider the following code snippet: age = int(input("Enter your age: ")) if age < 10 : print("Child") if age < 30 : print("Young Adult") if age < 70 : print("Old") if age < 100 : print("Impressively old") Assuming that the user inputs 80 as the age, what is the output? answers: a. Impressively old b. Child Young adult Old c. Child Young adult Old Impressive old d. Young adult Old

a. Impressively old

What does the following code snippet display? for n in range(1, 11) : for x in range(1, 11) : print(n*x, end = " ") print() answers: a. It displays a multiplication table for numbers 1-10 times 1-10 b. Nothing because it has compilation error. c. It displays a multiplication table for numbers 1-11 times 1-11 d.It displays a table of all numbers squared from 1-10

a. It displays a multiplication table for numbers 1-10 times 1-10

What will be the output of the following code snippet? token = False while token : print("Hello") answers: a. No output after successful compilation. b. "Hello" will be displayed only once. c. "Hello" will continue to be displayed until the user stops the program. d. No output because of compilation error.

a. No output after successful compilation.

What is printed from the following code snippet: message = "ho.." print(message * 3) answers: a. ho..ho..ho.. b. ho.. c. nothing is printed, this code snippet causes an error d. ho..ho..ho

a. ho..ho..ho..

Consider the following code snippet. What should be placed in the blank to cause a message to be displayed when the user enters the same letter twice in a row? letter = input("Enter the next letter in the alphabet: ") while letter != "": previous = letter letter = input("Enter the next letter") if ________________________ : print("Duplicate input") answers: a. letter == previous b. alphabet[0] == letter c. alphabet[0] == previous d. letter == letter

a. letter == previous

Which of the following statements correctly multiplies num1 times num2? answers: a. num1 * num2 b. num1 · num2 c. num1 ** num2 d. num1 x num2

a. num1 * num2

Consider the following code snippet. num1 = 0 num2 = 0 num3 = 0 num4 = 0 num5 = 0 num1 = int(input("Enter a number: ")) num2 = int(input("Enter a number: ")) if num1 < num2 : num3 = num1 else : num3 = num2 if num1 < num2 + 10 : num4 = num1 elif num1 < num2 + 20 : num5 = num1 print("num1 =", num1, "num2 =", num2, "num3 =", num3, "num4 =", num4, "num5 =", num5) Assuming that the user enters the numbers 20 and 12 as the two input values, what is the output of the code snippet? answers: a. num1 = 20 num2 = 12 num3 = 12 num4 = 20 num5 = 0 b. num1 = 20 num2 = 12 num3 = 12 num4 = 0 num5 = 20 c. num1 = 20 num2 = 12 num3 = 20 num4 = 0 num5 = 20 d. num1 = 20 num2 = 12 num3 = 20 num4 = 20 num5 = 0

a. num1 = 20 num2 = 12 num3 = 12 num4 = 20 num5 = 0

What is the output of the following code fragment? i = 1 sum = 0 while i <= 15 : sum = sum + i i = i + 1 print("The value of sum is", sum) answer: a. The value of sum is 120 b. The value of sum is 0 c. The value of sum is 136 d. The value of sum is 105

a. the value of sum is 120

the absolute value of x

abs(x)

The if statement

allows a program to carry out different actions depending on the nature of the data to be processed

two boolean operators

and, or

A storyboard consists of

annotated sketches for each step in an action sequence

Built in functions

are a small set of functions that are defined as part of the python language (can be used without importing any modules)

What is the sentinel value in the following code segment? value = 15 x = int(input("Enter an integer: ")) while x != 0 : value = value * 2 print(value + 3) x = int(input("Enter an integer: ")) answers: a. 2 b. 0 c. 3 d. 15

b. 0

What are the two parts of an if statement? answers: a. A check and an increment b. A condition and a body c. An increment and a return value d. An increment and a body

b. A condition and a bod

A loop inside another loop is called: answers: a. A while loop b. A nested loop c. A parallel loop d. A sentinel loop

b. A nested loop

Which of the following variables is used to store a condition that can be either True or False? answers: a. Conditional b. Boolean c. Algebraic d. Logical

b. Boolean

Which statement corrects the off-by-one error in the following code: # This code prints the first 10 numbers starting with zero i = 0 while i <= 10 : print(i) i = i + 1 answers: a. Replace i = i + 1 with i = i + 2 b. Replace while i <= 10 with while i < 10 c. Replace i = 0 with i = 1 d. Replace while i <= 10 with while i + 1< 10

b. Replace while i <= 10 with while i < 1

What will be the final output of the following code snippet when a user enters input values in the order 10, 20, 30, 40, 50, and -1? sum = 0 count = 0 salary = 0 average = 0 while salary != -1 : salary = float(input("Enter salaries (-1 to stop): ")) if salary != -1 : sum = sum + salary count = count + 1 if count > 0 : average = sum / count print("The average salary: ", average) else : print("No data!") answers: a. There will be no output as the code snippet will not compile. b. The average salary: 30.0 c. The average salary: 0.0 d. The average salary: 24.83333

b. The average salary: 30.0

When hand-tracing the loop in the code snippet below, which variables are important to evaluate? i = 10 j = 5 k = -10 sum = 0 while i > 0 : sum = sum + i + j i = i - 1 print("Iteration: ", i) answers: a. The variables j and k b. The variables i and sum c. The variables i, j, and k d. The variables i and j

b. The variables i and sum

What is printed by the following code snippet if itemCount contains a value of 10 and cost contains 80: if itemCount > 5 : discount = 0.8 totalCost = cost * discount print("Total discounted price is:", totalCost) answers: a. Total discounted price is: 16.0 b. Total discounted price is: 64.0 c. Nothing, the program will run but not print any results d. Total discounted price is: 0.0

b. Total discounted price is: 64.0

Suppose you must design a program to calculate the roll-out (number of inches traveled in one revolution of the pedals of a bicycle based on its gear combinations). The user must provide the gear sizes, which must be converted into roll-out for all different gear combinations. How can the flow of user interaction for this problem be designed? answers: a. The physical gears can lead to ideas for the correct algorithm to use. b. A storyboard can be used. c. Pseudocode can guide algorithm design through divide-and-conquer strategy. d. Hand-tracing can confirm code that implements gear selection.

b. a storyboard can be used

The following program is supposed to print a message any time the user enters two consecutive values that are the same. What line of code must be inserted in the blank so that the program will achieve this goal? value = int(input("Enter a value: ") inputStr = input("Enter a value: ") while inputStr != "" : previous = value value = int(inputStr) ____________________ print("Found consecutive values that are the same") inputStr = input("Enter a value: ") answers: a. if previous == inputStr : b. if previous == value : c. if value == input : d. if value == inputStr :

b. if previous == value :

What will be the values of the variables num1 and num2 after the given set of assignments? num1 = 20 num2 = 10 num1 = num1 + num2 / 2 num2 = num1 answers: a. num1 = 15.0, num2 = 15.0 b. num1 = 25.0, num2 = 25.0 c. num1 = 15.0, num2 = 10.0 d. num1 = 20.0, num2 = 10.0

b. num1 = 25.0, num2 = 25.0

Which code snippet is the correct Python equivalent to the following Algebraic expression ? c = √(a2 + b2) answers: a. sqrt(a ^ 2 + b ^ 2) b. sqrt(a ** 2 + b ** 2) c. squareroot(a ** 2 + b ** 2) d. sqrt(a * 2 + b * 2)

b. sqrt(a ** 2 + b ** 2)

What value is displayed by the following code segment? s = "Computer Science" x = s.find("TER") print(x) answers: a. 0 b. 5 c. -1 d. 6

c. -1

What is the output of the code snippet given below? s = "12345" i = 0 while i < 5 : print(s[i]) i = i + 1 answers: a. 2345 b. No output c. 12345 d. 1234

c. 12345

Assuming a user enters 30, 20, and 10 as the input values, what is the output of the following code snippet? num1 = int(input("Enter a number: ")) num2 = int(input("Enter a number: ")) num3 = int(input("Enter a number: ")) if num1 > num2 : if num1 > num3 : print(num1) else : print(num3) else : if num2 > num3 : print(num2) else : print(num3) answers: a. 0 b. 20 c. 30 d. 10

c. 30

What is the value of i at the end of the following code segment? i = 1 while i < 32 : i = i * 2 answers: a. 16 b. 31 c. 32 d. 64

c. 32

What are the final values of the variables i, j, and n at the end of this loop? i = 0 j = 12 n = 0 while i != j : i = i + 2 j = j - 2 n = n + 1 answers: a. 0, 12, 0 b. 4, 8, 2 c. 6, 6, 3 d. 2, 10, 1

c. 6 6 3

What is the wrong with the following code snippet? grade = int(input("Enter student grade: ")) if grade >= 90 : letterGrade = "A" if grade >= 80 : letterGrade = "B" if grade >= 70 : letterGrade = "C" if grade >= 60 : letterGrade = "D" else : letterGrade = "E" print(letterGrade) answer: a. Everyone will get an "E" b. The code block will not compile c. Anyone with a grade higher than 60 will receive a "D" d. Nothing is wrong, students will get the correct grade

c. Anyone with a grade higher than 60 will receive a "D"

When will the loop in the following code snippet stop? sum = 0 count = 1 str = input("Enter values, Q to quit: ") while count < 100 and str != "Q" : value = float(str) sum = sum + value count = count + 1 str = input("Enter values, Q to quit: ") I. When the user enters an integer II. When the user enters the character Q III. After the user enters 100 numbers answers: a. I or II b. III only c. II or III d. II only

c. II or III

What is the output of the code snippet given below? s = "abcde" length = len(s) i = 1 while i < length : print(s[i]) i = i + 1 a. abcd b. abcde c. bcde d. No output

c. bcde

Given that the following code snippet: isFelon = False answer = input("have you ever committed a felony? ") if answer == "Yes" or answer == "yes" : isFelon = True age = int(input("what is your age? ")) which statement assigns the variable mayVote a value of True if a person may vote if they are 18 or older and not a felon? answers: a. mayVote = age > 18 or not isFelon b. mayVote = not ( age >= 18 and isFelon) c. mayVote = age >= 18 and not isFelon d. mayVote = not ( age >= 18 or isFelon)

c. mayVote = age >= 18 and not isFelon

Equality testing

checks if something is true

Hardware

consists of the physical elements in a computer system

the cosine of x in radians

cos(x)

Of the following options, what should the user enter to cause the following while loop to terminate? done = False while not done : x = float(input("Enter a number: ")) if x > 5.0 : print(x) elif x > 0.0 : done = False elif x < -5.0 : print(-x) else : done = True answers: a. 7.5 b. -7.5 c. 2.5 d. -2.5

d. -2.5

What will be printed by the statements below? for ctr in range(10, 5, -1) : print(ctr, end = " ") answer choices: a. 5, 6, 7, 8, 9, 10 b. 10, 9, 8, 7, 6, 5 c. 6, 7, 8, 9, 10 d. 10, 9, 8, 7, 6

d. 10, 9, 8, 7, 6

What is the output of this loop? counter = 1 for i in range(1, 100) : counter = counter + 1 print(counter) answers: a. 10 b. 49 c. 60 d. 100

d. 100

How many times does the following code fragment display "Hi"? i = 10 while i >= 0 : print("Hi") i = i - 1 a. 12 times b. 10 times c. 9 times d. 11 times

d. 11 times

Given the following code snippet: MIN_SPEED = 45 MAX_SPEED = 65 speed = 55 if not (speed < MAX_SPEED) : speed = speed - 10 if not (speed > MIN_SPEED) : speed = speed + 10 print(speed) what output is produced? answers: a. 50 b. 45 c. 65 d. 55

d. 55

Which of the following correctly identifies what is wrong with the code snippet below: if y > 300 : x = y else : x = 0 print("x:", x) answers: a. No colon is needed after the else statement b. Nothing, the program runs as intended c. The statement after the if statement must be indented d. The statement after the if statement and the statement after the else statement must be indented

d. The statement after the if statement and the statement after the else statement must be indented

What is the output of the code snippet given below? s = "abcde" j = len(s) - 1 while j >= 0 : print(s[j]) j = j - 1 answers: a. abcd b. bcde c. bcbcd d. edcba

d. edcba

What function is used to read a value from the keyboard? answers: a. print b. keyboard c. next d. input

d. input

What is printed by the following code snippet: street = " Main Street" address = 123 + street print(address) answers: a. 123Main Street b. 123 "Main Street" c. 123 Main Street d. nothing is printed, this code snippet causes an error

d. nothing is printed, this code snippet causes an error

What string method can be used to determine if all characters within a string are lowercase? answers: a. text.isdigit() b. text.isalnum() c. text.isalpha() d. text.islower()

d. text.islower()

Which statement about this code snippet is accurate? years = 50 balance = 10000 targetBalance = 20000 rate = 3 for i in range(1 , years + 1) : if balance >= targetBalance : i = years + 1 else : interest = balance * rate / 100 balance = balance + interest answers: a. The loop will run at most 50 times, but may stop earlier when balance exceeds or equals targetBalance. b. There is a compilation error. c. The loop will never stop. d. The loop will run 50 times.

d. the loop will run 50 times.

converts x from radians to degrees

degrees(x)

==

equal

e^x

exp(x)

pseudocode

half way between natural language and a programming language. The steps that the pseudocode describes must be: unambiguous, executable, terminating.

The two keywords of the if statement are

if, else

the natural logarithm of x (to base e) or the logarithm of x given the base

log(x) and log(x, base)

Assignment

makes something true

!=

not equal

Use the str() function to convert between

numbers and strings

boolean variable

often called a flag because it can either be up (true) or down (false)

Statement blocks signal that

one or more statements are part of a given compound statement

Central processing unit

performs program control and data processing

Steps to writing a loop

planning : 1. Decide what work to do inside the loop 2. Specify the loop condition 3. Determine loop type 4. Setup variables before the first loop 5. Process results when the loop is finished 6. Trace the loop with typical examples Coding: 7. Implement the loop in python

two types of storage

primary and secondary

converts x degrees into radians

radians (x)

Nested decisions

required for problems that have two levels of decision making

the floating-point value x rounded to a whole number or to n places

round(x) or round(x, n)

the sine of x in radians

sin(x)

the tangent of x in radians

tan(x)

Computer program

tells a computer the sequence of steps needed to complete a specific task

Total += cans is a shortcut for

total = total + cans

truncates floating-point value x to an integer

trunc(x)

The for loop

used to iterate over the contents of any container

Nested branches

when a decision statement is contained inside the branch of another decision statement

s.isspace()

Returns true if string s consists of only white space characters (blank, new line, tab) and it contains at least one character. Otherwise it returns false.

s.islower()

Returns true if string s contains at least one letter and all letters in the string are lower case. Otherwise it returns false.

s.isupper()

Returns true if string s contains at least one letter and all letters in the string are uppercase. Otherwise it returns false

s.isdigit()

Returns true is string s consists only of digits and contains at least one character. Otherwise it returns false

Elif statement

Short for else, if.. As soon as one on the test conditions succeeds, the statement block is executed No other tests are attempted If none of the test conditions succeed the final else clause is executed

Compile-time errors

Syntax errors Spelling, capitalization, punctuation Ordering of statements, matching parenthesis, quotes, etc....

Programming

The act of designing, implementing, and testing computer programs

Logic errors

The program runs, but produces unintended results The program may ' crash'

How many times is the text "Let's have fun with Python." printed when this code snippet is run? i = 0 while i <= 10 : print("Let's have fun with Python.") i = i + 1 if i % 2 == 0 : i = 10 answers: A. 3 B. 2 C. 1 D. 10

A. 3

<

Less than

<=

Less than or equal

s.isalpha()

Returns true if string s consists of only letters and contains at least one character. Otherwise it returns false

s.isalnum()

Returns true if string s consists of only letters or digits and it contains at least one character, otherwise it returns false.