Variables and Constants in Programming

Question 1

What is a problem (in the context of programming?

Answer 1

a specific task that a computer program is designed to solve with a logical solution with a set of STEPS in an algorithm (ex. counting students)

Question 2

What are the steps of problem analysis?

Answer 2

• can it be broken down into smaller parts
• can certain steps be ignored
• can the outcome be predicted
• is the solution optimal

Question 3

How can generality and flexibility be achieved in a program?

Answer 3

using VARIABLES to store numbers and allowing user to INPUT the numbers at runtime (as the program runs)

Question 4

What is a VARIABLE?

Answer 4

NAMED STORAGE location in a computer program

Question 5

How do you define a variable on Python?

Answer 5

tell python:
1. what named it is referred to
2. initial value of the variable

Question 6

How do you place a value into a variable?

Answer 6

assignment statement (define the variable)

with an assignment statement

ex.
#assignment statement (define the variable)
x=5

Question 7

is the = sign used for comparison?

Answer 7

NO! it is an assignment statement, - it copies the value on the right side into the variable on the left side

Question 8

Should the variable always be x?

Answer 8

NO! variable names should describe the purpose of the variable
ex studentGPA vs sgpa

Question 9

What are the Variable Name rules?

Answer 9

1. start with lowercase or underscore
2. not spaces
3. separate words with ‘camelCase’ notation
4. don’t use ‘reserved’ python words (ex. print, input)
5. letters numbers and underscore only
6. cannot use / or .

Question 10

What is the undefined variable error?

Answer 10

must define variable before you use it above the line of code where you 1st use the variable

ex. literPerOunce = 0.0296
canVolume = 12*literPerOunce

Question 11

What are the three data types in python?

Answer 11

integer or int - whole number
float - fraction part
string - sequence of characters

Question 12

how can you accept input from a user?

Answer 12

built-in function used to read a STRING from standard input

input()

Question 13

what is the syntax of input?

Answer 13

variable = input(argument)

x=input(‘enter a value:’
print(‘you entered:’,x)

Question 14

What data type is the input () function default?

Answer 14

string

Question 15

How can you have python read a number from a user?

Answer 15

typecast the string into int or float with int() and float() functions

x=int(input(‘integer:’)
x=float(input(‘fraction:’)

Question 16

What happens when you update a variable?

Answer 16

the new value assignment of a variable replaces the previous contents of the variable

Question 17

What are the steps to update a variable to assign a value?

Answer 17

1. calculate right-side of the assignment
2. store the result in the variable names on the left-hand side of the assignment operator

Question 18

Can a variable be assigned different values at different places?

Answer 18

YES; data type (string, float, int) is associated with the VALUE, NOT the variable, so the variable can be associated with a string and float and int at different places
–> if you use a variable and it has an unexpected type, there will be an error

Question 19

What is a constant?

Answer 19

VARAIBLE that should not be changed after it’s assigned an initial value

Question 20

How are constants named?

Answer 20

Capitalized! name constants to explain numerical values to be used in calculations

Question 21

what are unexpected types of data that will result in error?

Answer 21

fractions and numbers with commas