3.1.1 - Data Types and Variables

Variables - abstraction that holds value

Data Types:

  • integer - numbers
  • string - text/letters
  • boolean - true/false statements

Hacks:

3.1.2 - Variables

Storing Values:

  • Collegeboard: <–
  • Python: =

Hacks:

  1. In your own words, briefly explain by writing down what an assignment operator is.
    • It is what is used to assign a certain integer or string into a variable. This is known as an equals sign (=) in Python.
  2. In Collegeboard pseudocode, what symbol is used to assign values to variables?
    • An arrow pointing to the left (<–) is used to assign values to variables.
  3. A variable, x, is initially given a value of 15. Later on, the value for x is changed to 22. If you print x, would the command display 15 or 22?
    • The value outputted would be 22, since the latest assignment of x is 22.

3.2.1 - List and Strings Using Variables

Strings - numbers, letters, characters that can be printed

print("Hello World")

# Hello World

Lists - allow for multiple strings to be put together into a form that is easily accessible

list = ["red", "orange", "yelllow"]

print(list)

# ["red", "orange", "yelllow"]

List Index - allows to access one element in a list with integers

list = ["red", "orange", "yelllow"]

print(list[2])

# ["orange"]

Hacks

  1. What is a list?
    • A list is a set of strings that are placed under the name of a single variable, leading to an easy way to store data.
  2. What is an element?
    • An element is one of the many strings that makes up a list. These can be called out and printed, leading to easily storing a lot of data.
  3. What is an easy way to reference the elements in a list or string?
    • An easy way to reference the elements is to print the variable, followed by an integer, which is how the elements are indexed in the list.
  4. What is an example of a string?
    • A string is text that is defined as a variable or an element in a list. This can be directly printed with a print function.

3.2.2 - Data Abstraction with Lists

Abstraction - allows for use input to make an output

  • the inputs are put into a list and then outputted with the modified values

Hacks

3.2.3 - Managing Complexity with Lists

Complexity - lists allow for a lot of data to be stored into one line of code, allowing for cleaner code and less work with creating variables

Hacks

Why are using lists better for a program, rather than writing out each line of code?

  • Lists are better for a program because they allow for the programmer to store more data into one line of code and then easily find it with indexing.

3.3.1 - Algorithms Using Sequences

Algorithm - set of instructions that accomplish a task

  • sequencing - creating a series of steps to be executed by code
  • selection - making a decision with code (yes or no)
  • iteration - loop that is triggered if a certain condition is met and stopped if it isn’t (loops until a certain action is done)

Hacks

  • Sequencing: This is where the code is set up in a number of steps, which are done in a certain order in order to achieve an end process.
  • Selection: One selection is in step 4, where if number = item, the program will display item found. Another selection is where if more numbers are in the list, then the program goes back to step 2.
  • Iteration: An iteration is where the program makes a selection in step 4 and then if certain conditions are met, the program starts at step 2 again, up until it ends the list.

3.3.2 - Mathematical Expressions

Sequential Code Segments - code segments that are put in a certain order and execute their tasks in that certain order

Collegeboard sample code:

Num1 - 25
Num2 -32
Num3 - 42
Average - (num1 + num2 + num3)/3
DISPLAY (Average)

3.3.3 - Evaluating Mathematical Expressions

  • Addition: a+b
  • Subtraction: a-b
  • Multiplication: a*b
  • Division: a/b
  • Modulus: a MOD b (a and b can be string or number)
num1 = 10
num2 = 5
num3 = 7

result = num1 + num2 + num3

print(result)

# 22

Using MOD:

num1 = 12
num2 = 25
num3 = 14

result = num1 / 4 * num3 + 9 % 2 - num3

print(result)

#29

Hacks

3 Across - Sequence 1 Down - Iteration 2 Down - Selection

3.4 - Expression Manipulates Strings

  • len (str)
    • returns the number of character is str
    • len(“hello”) returns 5
  • concat (str1, str2)
    • returns a single string consisting of str1 followed by str 2
    • concat(“hello”,”world”) return ‘hello world’
  • substring (str1, str2, length)
    • returns a substring of consecutive character from str1, starting the character at position ‘start’ and containing ‘length’ character
    • substring (“hello”,”world”, 4,5) returns ‘lo wor’

Hacks

3.5 - Expression Manipulates Strings

Booleans - algebraic notation to represent a logical decision in computing

  • expresses in true/false
  • used to test between two situations Relational Operators - mathematical relationships
  • determines true/false
  • a = b, a > b, a < b, etc. Logical Operators - not, or, and, nor, nand,…
  • NOT - displays opposite of data inputted, has no effect on var, mostly true/false
  • AND - evaluates two conditions and whether they are both met
  • OR - only outputs true if one of the conditions are met

Hacks

  • NOT - displays opposite of the input (ex. var = false --> NOT --> var = true)
  • AND - displays true if both conditions are met (ex. A = true, B = true --> A = true AND B = true --> True)
  • OR - displays true if one of the two conditions are met (ex. A = true, B = false --> A = true OR B = true --> true)

3.6 - Conditionals

Conditionals - selection in any language

  • Selection - selecting between true/false
  • Algorithm - set of instructions to complete task
  • Conditional Statements - if/then statements; checks whether something is true and decides what to do

Javascript Examples:

function isEven(parameter) {
    if (parameter % 2 == 0) {
        console.log("The number is even.");
    }
    else if (parameter % 2 != 0) {
        console.log("The number is odd.")
    }
}

isEven(4)

This shows how when a value is equal to 2 after modulus, then the output will show it’s even. If it’s not equal to 2 then the output will be odd.

3.7 - Nested Conditionals

Nested Conditionals - conditional within a conditional

  • else/if statements can nest statements as well

Nested Statements:

if (x = 1)
  print("1")
elif (x = 2)
  print("2")

Example with numbers:

x = 2
y = 3
if x == y:
    print("x and y are equal")
else:
    if x > y:
        print("x is bigger than y")
    elif x < y:
        print("x is smaller than y")

Hacks

score1 = 90
score2 = 62

start = input("Are you ready to start?")

proc = True

if start == "yes":
  if score1 >= 75:
    proc = True
  elif score1 < 75:
    print("What is your second score?")
    if score2 >= 75:
      proc = True
    else:
      proc = False
else:
  print("Restart")

if proc:
  print("You Passed!!!")
else:
  print("You Failed.")

You Passed!!!


num = 568

guess = 243 # guess number

start = input("Are you ready to start?")

correct = False

if start == "yes":
  if guess > num:
    proc = False
    print("too high")
  elif guess < num:
    if guess == num:
      proc = True
    else:
      proc = False
      print("too low")
else:
  print("Restart")

too low


x = 5

y = 34

start = input("Are you ready to start?")

if start == "yes":
  if x != 5:
    print("incorrect")
  else:
    if y != 34:
      print("incorrect")
    else:
      print("correct")
else:
  print("Restart")

correct

u = 19
v = 28
w = 85 # set as incorrect value
x = 5
y = 34
z = 57

start = input("Are you ready to start?")

if start == "yes":
  if u != 19:
    print("u is incorrect, can't proceed")
  elif v != 28:
    print("v is incorrect, can't proceed")
  elif w != 95:
    print("w is incorrect, can't proceed")
  elif x != 5:
    print("x is incorrect, can't proceed")
  elif y != 34:
    print("y is incorrect, can't proceed")
  elif z != 57:
    print("z is incorrect, can't proceed")
else:
  print("Restart")

w is incorrect, can't proceed

print("type in answers as 'y' or as 'n'")

math = input("Do you like math?")
writing = input("Do you like writing?")
science = input("Do you like science?")

mathc = ["Integrated 1-3", "Calculus AB", "Calculus BC", "Statistics"]
writingc = ["Honors English", "Honors Humanities", "English Language", "English Literature"]
sciencec = ["Chemistry 1-2", "Biology 1-2", "Physics 1-2", "AP Chemistry", "AP Biology", "AP Physics"]

print("Math: ", math)
print("Writing: ", writing)
print("Science: ", science)

if math == "y":
  print("You should take: ", mathc)
  if writing == "y":
    print("You should take: ", writingc)
  if science == "y":
    print("You should take: ", sciencec)
elif writing == "y":
  print("You should take: ", writingc)
  if science == "y":
    print("You should take: ", sciencec)
elif science == "y":
  print("You should take: ", sciencec)
else:
  print("dropout")

type in answers as 'y' or as 'n'
Math:  y
Writing:  y
Science:  n
You should take:  ['Integrated 1-3', 'Calculus AB', 'Calculus BC', 'Statistics']
You should take:  ['Honors English', 'Honors Humanities', 'English Language', 'English Literature']