Arithmetic, Relational & Logical Operations (Edexcel GCSE Computer Science)

Revision Note

What is an operator?

  • An operator is a symbol used to instruct a computer to perform a specific operation on one or more values

  • Examples of common operators include:

    • Arithmetic

    • Relational

    • Logical (AND, OR and NOT)

Arithmetic Operators

  • There are a range of arithmetic operators that must be used in programming questions

  • The table below summarises each of the operators

Operator

Python

Addition

+

Subtraction

-

Multiplication

*

Division

/

Modulus (remainder after division)

%

Quotient (whole number division)

//

Exponentiation (to the power of)

**

  • To demonstrate the use of common arithmetic operators, three sample programs written in Python are given below

  • Comments have been included to help understand how the arithmetic operators are being used

    • Arithmetic operators #1 - a simple program to calculate if a user-entered number is odd or even

    • Arithmetic operators #2 - a simple program to calculate the area of a circle from a user-inputted radius

    • Arithmetic operators #3 - a simple program that generates 5 maths questions based on user inputs and gives a score of how many were correctly answered at the end

Python code

# -----------------------------------------------------------------------
# Arithmetic operators #1
# -----------------------------------------------------------------------
# Get the user to input a number
user_input = int(input("Enter a number: "))

# if the remainder of the number divided by 2 is 0, the number is even
if user_input % 2 == 0:
    print("The number is even.")
else:
    print("The number is odd.")

# -----------------------------------------------------------------------
# Arithmetic operators #2
# -----------------------------------------------------------------------
# Get the radius from the user
radius = float(input("Enter the radius of the circle: "))

# Calculate the area of the circle
area = 3.14159 * radius ** 2

# Display the calculated area
print("The area of the circle with radius",radius,"is",area)

# ------------------------------------------------------------------------
# Arithmetic operators #3
# ------------------------------------------------------------------------
# Set the score to 0
score = 0

# Loop 5 times
for x in range(5):
    num1 = int(input("Enter the first number: "))
    operator = input("Enter the operator (+, -, *): ")
    num2 = int(input("Enter the second number: "))
    user_answer = int(input("What is "+str(num1)+str(operator)+str(num2)+"? "))

# Check the answer and update the score
    if operator == '+':
        correct_answer = num1 + num2
    elif operator == '-':
        correct_answer = num1 - num2
    elif operator == '*':
        correct_answer = num1 * num2

    if user_answer == correct_answer:
        score = score + 1
    else:
      print("Sorry that's incorrect.")

print("Your score is:", score)

Relational Operators & Logical Operations

  • There are a range of relational and logical operators that must be used in programming questions

  • The tables below summarise each of the operators

Relational Operators

Operator

Python

Equal to

==

Not equal to

!=

Less than

<

Less than or equal to

<=

Greater than

>

Greater than or equal to

>=

Logical Operators

  • Logical operators can be categorised into three

    • AND

    • OR

    • NOT

  • Logical operators are always used alongside relational operators to form a comparison, some examples of this are:

    1. If number > 5 AND number <10:
      print("Valid number")

    2. If number <0 OR number >11:
      print("You are outside the range, try again")

Examples

Operator

Python

Addition

sum = 2 + 2 # 4

Multiplication

sum = 3 * 4 # 12

Modulus

sum = 10 % 3 # 1

Quotient

sum = 10 // 3 # 3

Exponentiation

sum = 2 ** 2 # 4

Equal to

if 3 == 3: # True

Not equal to

if 5 != 6: # True

Greater than or equal to

if 10 >= 2: # True

AND

number = 10
if number > 0 and number < 20:
# True

  • To demonstrate the use of common operators, three sample programs written in Python are given below

  • Comments have been included to help understand how the operators are being used

    • Common operators #1 - a simple program that assigns Boolean values to two variables and outputs basic comparisons

    • Common operators #2 - a simple program to output a grade based on a users score

    • Common operators #3 - a simple program reads a text files and searches for an inputted score

Python code

# -----------------------------------------------------------
# Common operators #1
# -----------------------------------------------------------
# Assign a Boolean value to a and b
a = True
b = False

# print the result of a and b
print("a and b:", a and b)
# print the result of a or b
print("a or b:", a or b)
# print the result of not a
print("not a:", not a)

# -----------------------------------------------------------
# Common operators #2
# -----------------------------------------------------------

# Take input for the score from the user
score = int(input("Enter the score: "))

# Compare the score and output the corresponding grade
if score >= 90 and score <= 100:
  print("Grade: A")
elif score >= 80 and score < 90:
  print("Grade: B")
elif score >= 70 and score < 80:
  print("Grade: C")
elif score < 70:
  print("Fail")

# -----------------------------------------------------------
# Common operators #3
# -----------------------------------------------------------
# Open the file for reading
file = open("scores.txt","r")
# Set flags to false
end_of_file = False
found = False
score = input("Enter a score: ")
# While it's not the end of the file and the score has not been found
while not end_of_file and not found:
  # read the line
  scores = file.readline().strip()
  # if the line equals the score
  if score == str(scores):
    found = True
    print("Score found")
  # if the line is empty
  if scores == "":
    end_of_file = True
    print("Score not found")
file.close()

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