Chapter 2

Question 1

What is a variable? What are the different types?

Answer 1

A variable is a place to store information. There are integers (int) floating point numbers, strings, etc.

Question 2

What are assignment statements and what do they do?

Answer 2

They store the value of an expression in a variable and replaces the previously stored value. When you set a variable equal to something, that is called an initialization.

EX: variable = statement;

Question 3

What factors are and aren’t allowed when naming a variable?

Answer 3

• Variables are case sensitive
• Variables should have descriptive names
  Cans:
• numbers
• letters
• underscores_

Cannot:
- symbols (!, $, %)
- spaces
- reserved words (int, double, include)
- start with a number

Question 4

Examples on naming variables: legal or illegal?

• Day_Of_Week
• 3dGraph
• _employee_num
• June1997
• MixedUp#3

Answer 4

• Day_Of_Week // legal
• 3dGraph // illegal
• _employee_num // legal, not recommended
• June1997 // legal
• MixedUp#3 // illegal

Question 5

What are the different data types we deal with?

Answer 5

• Number data types (int, double, etc)
• Characters
• Booleans

Question 6

What’s the difference between integers and doubles?

Answer 6

Integers are whole numbers while doubles are decimal numbers

Question 7

What does the boolean type mean?

Answer 7

True or false

Question 8

What are character types used for?

Answer 8

Make sure to use single quotations to denote

• They are used to store a single character such as ‘X’ or ‘$’

Question 9

Why do overflow errors occur?

Answer 9

An overflow error is when the number is too large and the numeric type can’t store it.

Question 10

Why do underflow errors occur?

Answer 10

Usually happens for floating types like doubles

• They occur when the result is too small to be represented in the type being returned by the function.

Question 11

What is casting?

Answer 11

Casting is a conversion between different data types.

It is better to use explicit casting rather than implicit casting bc info can be easily lost

Explicit Casting Format: static_cast<data> ()</data>

EX: int n = static_cast<int> (10.9);
- n now holds 10</int>

Question 12

What is an roundoff error?

Answer 12

Roundoff errors happen bc some numbers can’t be precisely represented with the binary

A trick to solve this is to +0.5

Question 13

How is arithmetic evaluated in C
++?

Answer 13

They are evaluated with the same rules in mathematics. Follow PEMDAS!

Question 14

Compare post increment vs. pre increment. (x++ vs. ++x)

Answer 14

Post increment is when the incrementation occurs after the command, while pre incrementation occurs before the command. The same goes for pre/post decrementation

Question 15

Division vs. Mod (%)

Answer 15

Division gives us the number after dividing two numbers. % gives us the remainder after dividing two integers. If the remainder is 0, that means both integers are even.

If the numerator is less than the denominator, the % is equal to the numerator

Question 16

What C++ library must be used when using math functions?

Answer 16

<cmath> : defines many mathematical functions such as sqrt (square root) and pow (raising to a power)

Should look like #include <cmath>
</cmath></cmath>

Question 17

What are constants?

Answer 17

Constants are values that cannot be changed

Question 18

How can constants be distinguished?

Answer 18

They are typically written in capital letters to be distinguished

EX: there will always be 365 days in a year, so we may use const int YEAR = 365;

Question 19

What are magic numbers and why should they be avoided?

Answer 19

Magic numbers are a numeric constant that appears in your code without explanation. Avoiding them limit confusion.

Question 20

What are string literals?

Answer 20

String literals are a sequence of characters enclosed in quotation marks.

EX: cout &laquo_space;“I love programming!”;
*notice how the quotations appear on the same line.”

Question 21

What C++ library must be used when dealing with strings

Answer 21

We must use <string>. Don't forget to include using namespace std;</string>

Question 22

What are string variables?

Answer 22

String variables are variables that store string literals. String literals are a sequence of characters that are enclosed within quotation marks.

*Strings can hold letters, numbers, spaces, and symbols (periods, commas, exclamation, question mark, addition, etc)

Question 23

Explain the difference between strings and chars

Answer 23

Strings can hold a sequence of characters while chars can only hold one character. You can tell the difference by looking at the quotation marks. Strings will always have the double quotation (“ “), while chars will always have the single quotations. (‘ ‘)

Question 24

What is concatenation?

Answer 24

Concatenation is a form of string manipulation. We use the + operator to add different strings together.

EX:
{ string s1, s2, s3, s4;
s1 = “Hello “;
s2 = “every”;
s3= “one!”;
s4= s1+ s2+ s3;
coud &laquo_space;s4 &laquo_space;endl;
return 0; }

Output: Hello everyone!

Question 25

What is the function of string.length()?

Answer 25

string.length() finds the length of characters that are in your string. You can fill in the parenthesis to find specific characters of your string.

If the length is 0, that is called an empty string

Question 26

Explain the string manipulation: operator [ ].

Answer 26

The operator [ ] returns individual characters of a string, and is also called subscript or array index operator

In C++, counting starts at 0

EX:
string s = “Hello”;
char c = s[0]; // c holds H

H E L L O
0 1 2 3 4

Question 27

Explain the string manipulation: substring.

Answer 27

name.substr(i); - substring starting at position i until the end

name.substr(i, n) - substring starting at position i until length n

Question 28

Explain the string manipulation: erase

Answer 28

name.erase(i) - erase all characters starting from index i to the end

name.erase(i,n) - erase at most n characters starting at index i

Question 29

What do we use to allow user keyboard input? What happens if the buffer is empty?

Answer 29

cin&raquo_space; variable1

*Can also be chained and look like this: cin&raquo_space; variable1&raquo_space; variable2&raquo_space; … *

If the buffer is empty, the program stops until there is keyboard input (hitting the enter key)

Question 30

What is getline? When is it used?

Answer 30

Because cin skips white spaces (if it is a string), we need to use getline in order to read the white spaces. Without getline, only the first word will be read

Getline can only read strings or interpret input as strings

Format: getline (cin, s);

Question 31

What is cin buffer?

Answer 31

Cin buffer is a temporary storage space to hold all inputs entered by cin

Ex:
int m=100, n = 1;
double x = 0.5;
cin&raquo_space; m&raquo_space; n&raquo_space; x; cout &laquo_space;m &laquo_space;“ ” &laquo_space;n &laquo_space;“ ” &laquo_space;x &laquo_space;endl;
input: 3.14 // 3 is assigned to m, but there is an error for n because there is a dot instead of an integer so it gives 0 and 0.5 is assigned to x

output: 3 0 0.5

Question 32

What are input failure flags and how do we implement them in our code?

Answer 32

cin.fail() is used to detect if the user inputs something we are not looking for.

cin.fail() returns true if the reading fails, and returns false if the reading is successful

We also have cin.clear() which is used to reset the flag to false (0), but doesn’t change the existing input in the buffer

we use cin.ignore or getline to empty the buffer

Question 33

Explain setw(n)

Answer 33

Library: #include <iomanip></iomanip>

Format: cout &laquo_space;setw(n) &laquo_space;variable1;

setw stands for set width, and n is an integer that represents the minimum width for the next output operation

Used for making rows and columns, padding/ spacing, output alignment, etc.

Question 34

What is setpercision(n) used for?

Answer 34

Helps with precision when it comes to floating point values (decimals) when they are being displayed so that there are at most n significant digits

Ex:
double a = 123.123456789;
double b = 123.1;
cout &laquo_space;setprecision(5) &laquo_space;a &laquo_space;“ ” &laquo_space;b;
// output 123.12 123.1

Question 35

What does using fixed with setprecision(n) do?

Answer 35

Using fixed with setprecision(n), it shows you up to n digits after the decimal point.

fixed doesn’t mofidfy variable values. All numbers are rounded in display.

Format: cout &laquo_space;fixed

EX:
double a = 123.123456789;
double b = 123.1;
cout &laquo_space;fixed &laquo_space;setprecision(5) &laquo_space;a &laquo_space;“ ” &laquo_space;b;
// output 123.12346 123.10000

b is 123.10000 because fixed uses 0 as padding as needed

Question 36

What is boolalpha used for?

Answer 36

Booleans output 0 for false, and 1 for true, but when we use boolalpha, we will receive an output that says true or false rahter than 0 and 1.

*If you want to switch back to 0 and 1, you can use noboolalpha to do so *