Data Types (OCR A Level Computer Science)

Data Types

What is a Data Type?

• A data type is a classification of data into groups according to the kind of data they represent

• Computers use different data types to represent different types of data in a program

• The basic data types include:

  • Integer: used to represent whole numbers, either positive or negative

    • Examples: 10, -5, 0

  • Real: used to represent numbers with a fractional part, either positive or negative

    • Examples: 3.14, -2.5, 0.0

  • Char: used to represent a single character such as a letter, digit or symbol

    • Examples: 'a', 'B', '5', '$'

  • String: used to represent a sequence of characters

    • Examples: "Hello World", "1234", "@#$%"

  • Boolean: used to represent true or false values

    • Examples: True, False

• It is important to choose the correct data type for a given situation to ensure accuracy and efficiency in the program

What is Casting?

• Casting is when you convert one data type to another data type

• When a user enters data into a program, this will more than likely be in a string format

• It's essential to convert some of this string data to a numerical format where possible

• For example, you may want to perform calculations on age-related data to determine if someone is eligible to vote

• Some programming languages can't execute numerical comparisons on text data, making this transformation crucial

• For example if you had "12" stored as a string and you wanted to know if this value was below 20

• Therefore, the string value of "12" will need to be cast as an integer to allow the comparison to take place

Python example

int_value = int("123") // converts the string "123" to 123

float_value = float("3.14") // converts the string "3.14" to 3.14

Java example

int intValue = Integer.parseInt("123"); // converts the string "123" to 123

double doubleValue = Double.parseDouble("3.14"); // converts the string "3.14" to 3.14

Casting between data types

int_value = 5

real_value = float(int_value)

real_value = 5.7

int_value = int(real_value)

int_str = "10"

int_value = int(int_str)

value = 5

str_value = str(value)

bool_val = True

str_val = str(bool_val)

bool_str = "True"

bool_val = bool(bool_str)