Data and structure types

• Declaring a variable


  The process of telling the computer what data type it is storing
• Categories of data

  • Text
  • Image
  • Number
  • Sound
• File types


  • .mp3
  • .jpg
  • .doc
  • .xls
• .mp3

  Storing and transferring music on computers, smartphones, online and portable MP3 players
• .jpg

  A widely used compressed image format for containing digital images
• .doc

  An attachment is simply an additional file sent with an email message/text
• .xls

  Used for files saved as Microsoft Excel worksheets
• .doc and .xls are likely to contain more than one type of data
• Data types that can be seen in a video game screenshot

  • Character
  • Integer
  • String
  • Boolean
• All data, whether they are text, audio, an image or a video, are stored as a series of 1s and 0s which the computer needs to know how to interpret
• Real numbers include integers, and a variable declared as a float could therefore hold an integer. More memory is used to store a float, so there is a separate data type of integers
• Integer

  Numeric variable without a decimal. Can be whole numbers and positive or negative. Can be written as "int" or integer
• Real (Float)


  Real numbers include all of the integer numbers that exist to infinity plus all of their fractions and decimals
• Character

  A character data type is used to store a single, alphanumeric character: a character representing a letter, number or symbol
• String

  A string is more useful than the character data type as it can hold a list of characters of any length: it therefore represents alphanumeric data and symbols
• Boolean


  The Boolean data type can only represent two values: true or false
• age


  Real (float)
• We do not explicitly specify the variable's data type in Python
• In most programming languages, string indexing starts at 0 so the first letter is at position 0. However, some languages start indexing at 1 and pseudocode can use string indexing beginning at either 0 or 1. In this book string indexing in pseudocode starts at 0
• String has been given a value
• 'found' hasn't been defined
• Should be an AND instead of OR
• Algorithm to count the number of times a particular character occurs in a string

  1. Inputchar = char(input("Please enter your character: "))

  2. Inputstring = str(input("Please enter your string: "))

  3. count = 0

  4. For char in Inputstring

  5. If char == Inputchar

  6. Count = count + 1

  7. print("You entered(Inputchar)(count)(times")
• Algorithm to check if the word 'variable' appears in a set of notes and count the number of times it appears


  1. notes = input"Enter your notes.")

  2. Count = cont.lower().count("variable")

  3. print(f"variable was in your notes{count}time(s)")
• Algorithm to allow a user to enter their first name and surname and print a message


  1. firstName = input("Please enter your first name: ")

  2. surname = input("Please enter your surname: ")

  3. print(f"Hello {firstName} {surname}. How are you?")
• Sometimes the computer can become confused as to whether a variable is a number or a string and produce an error message when a string is used in a mathematical calculation
• In some languages you cannot mix numbers, string and literal text in print statements. The numbers would have to be converted into strings using this method
• Data types include


  • Integer and real numbers
  • Characters
  • String
  • Boolean
• A real data type includes numbers with decimal places
• A string variable contains a list of characters
• Each character in a string has an index indicating its position
• String can be manipulated in many ways. For example, they can be split up or concatenated
• String can be converted to integer and real numbers and vice versa
• Real-world situations where storing multiple items of data is desirable

  • To store customer information
  • To store product details
  • To store order history
• Algorithm to ask a user to enter the names of five cars into an array and then print the array

  1. cars = []

  2. for i in range(5):

  3. car_name = input(f"Enter the name of car {i + 1} : ")

  4. cars.append(car_name)

  5. print("List of cars" , cars)
• Algorithm to return the array indexes of all the letters in a given string

  1. word = input(' enter word: ')

  2. for a in range (len(word)

  3. print(alphabet[word[a]], end =' ')
• Algorithm to find the minimum value and mean of an array of marks


  1. mark = []

  2. low = 0

  3. high = 100

  4. For i in marks:

  5. X = marks[i]

  6. IF high > low:

  7. i = i + 1

  8. ELIF high < high:

  9. high = x

  10. i = i + 1

  11. print("The lowest score is : ", low)

  12. print("The highest score is: ", high
• Algorithm to create a new array 'pass' and copy all the marks of 5 and over into this new array

  1. mark = [6, 9, 2, 5, 8, 3, 9, 9, 10 ,9, 5, 7, 10]

  2. pass = []
• Algorithm to amend all of the results in an array 'exam1' based on a new mark scheme

  1. exam1 = [1,2,4,7,99,23]

  2. newMarks = []

  3. for a in range(len(exam1)):

  4. if exam1[a] < 50:

  5. newMark = exam1[a] + 5

  6. newMarks.append(newMark)

  7. elif exam1[a] > 50:

  8. newMark = exam1[a] + 10

  9. newMarks.append(newMark)

  10. print(newMarks)
• Data structures

  • Lists
  • Tuples
  • Sets
  • Dictionaries