2.7: Data Types

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Overview

A data type is a classification of data which tells the compiler or interpreter how the programmer intends to use the data. Most programming languages support various types of data, including integer, real, character or string, and Boolean.^[1]

Discussion

Our interactions (inputs and outputs) with a program are treated in many languages as a stream of bytes. These bytes represent data that can be interpreted as representing values that we understand. Additionally, within a program, we process this data in various ways such as adding them up or sorting them. This data comes in different forms. Examples include:

your name – a string of characters
your age – usually an integer
the amount of money in your pocket – usually a value measured in dollars and cents (something with a fractional part)

A major part of understanding how to design and code programs is centered in understanding the types of data that we want to manipulate and how to manipulate that data.

Common data types include:

Data Type	Represents	Examples
integer	whole numbers	`-5`, `0`, `123`
floating point (real)	fractional numbers	`-87.5`, `0.0`, `3.14159`
string	A sequence of characters	`"Hello world!"`
Boolean	logical true or false	`true`, `false`
nothing	no data	`null`

The common data types usually exist in most programming languages and act or behave similarly from language to language. Additional complex and/or composite data types may exist and vary from language to language.

Pseudocode

Function Main
    ... This program demonstrates variables, literal constants, and data types.

    Declare Integer i
    Declare Real r
    Declare String s
    Declare Boolean b
    
    Assign i = 1234567890
    Assign r = 1.23456789012345
    Assign s = "string"
    Assign b = true

    Output "Integer i = " & i
    Output "Real r = " & r
    Output "String s = " & s
    Output "Boolean b = " & b
End

Output

Integer i = 1234567890
Real r = 1.23456789012345
String s = string
Boolean b = true

Flowchart

484px-Flowgorithm_Data_Types.svg_.png

Key Terms

Boolean: A data type representing logical true or false.

data type: Defines a set of values and a set of operations that can be applied on those values.

floating point: A data type representing numbers with fractional parts.

integer: A data type representing whole numbers.

string: A data type representing a sequence of characters.

References

Wikipedia: Data type ↵