This page was created with the assistance of GPT-5.6 Sol.

Data Types

After learning values are, it’s likely that you have already chosen a programming language.

Most general-purpose programming languages share a small set of common basic data types.

General-Purpose

If you choose a programming language that’s attractive to beginners, they are most definitely general-purpose. Domain-specific language (DSL) is another type of programming language. These languages cannot build any type of software (yes, even JavaScript, a general-purpose language can build an operating system that’s extremely inefficient).

An example DSL is CMake which is used to configure build files that create commands to compile code to binaries and link them to become an executable.

Your first language could be dynamically-typed where every variable’s type must be specified. For dynamically-typed languages, you still need to know the type of every single value you’re looking at in your code.

message = "hello"
# Variable message points to a value whose data type is a string.

char message[] = "hello";
// Variable message holds a value whose data type is an array of characters (string).

Basic Data Types

This page will detail out 3-4 very common basic data types. Another familiar term for basic data type is called a primitive data type though across languages whether something is a primitive data type varies.

Primitive In C/C++ vs. Python

People might consider the data type string as a primitive data type in Python. In C/C++ we atomize this down further more down to characters (we don’t have an explicit type called character in Python).

Here’s an example of how strings can be regarded as “primitive” in Python but not in C/C++.

char a[] = "I'm an array of characters";

a = "I'm a string but my individual character are still 'strings'"

Numbers

A computer is able to handle different types of numbers. Any general-purpose programming language should be able to handle integers and decimals. In an unmanaged language, there are data types available depending on how much memory is needed to be reserved for a certain number.

Unmanaged Languages

Examples of unmanaged language include C/C++, Rust… These languages require you to manage memory yourself. They are often statically-typed.

Integers

I would define these as non-decimal numbers. A typical integer can represent negative numbers as well. If an unmanaged language you can have different data types that can represent a varying ranges of numbers.

In C++, a standard int takes up about 4 bytes (32 bits) of memory. The range of numbers the int data type can represent is

What if you want to only have positive numbers? Well, you can use unsigned int in an unmanaged language like C/C++. First you don’t need to reserve a bit that says whether a number is positive or negative. Second, the highest positive number you can now represent is twice that of the int. The maximum range of values are now

Decimals

Decimal numbers are defined as numbers that have a fractional part behind it. In the United States we are part of the majority that use the dot as our separator between the whole and fractional part.

Ten-Thousand Comma/Dot Two-Hundred and Six

Dot or Comma? (TRIVIA)

In much of European countries and their former colonies (e.g. Vietnam and France), , is used as the separator between whole and fractional part while . is used as the separator between different orders of whole numbers.

In 1958, during the creation of the programming language ALGOL, there was a heavy dispute regarding the type of decimal system that must be used. The programming language releases accounted for regional difference in the number system. This was famous historical deadlock where neither side of the ALGOL committee (Americans vs. Europeans) yielded.

Nowadays most standard programming language uses the period decimal.

In C/C++, the two most utilized data types for decimal numbers are double and float.

• Float vs. Double

  The basic idea is that a float represents decimal numbers but a float can represent decimal numbers that are twice as big. The more digits the a number has (more so the fractional part), the more memory is needed to represent the number.

  Data Type Names Can Vary

  This distinction is not absolute for all programming languages. For example in Python, the data type float is implemented as a double in size.

Characters and Strings

Unmanaged languages most likely have the data type for a single character, usually called char. Computers are dumb so they don’t really understand any other symbols than binary representations of numbers.

In an unmanaged language like C/C++ or Rust, you are able to see that the data type char actually only stores number. The char becomes a number when a compiler is tasked to read from the translation unit and convert the character to a number according to the ASCII chart.

Translation Unit

In an unmanaged language, a translation unit is the collection of source code packaged together and processed by the compiler. In C/C++ this can be a single source file. For Rust, its fundamental translation unit is a crate.

// These two lines of code are valid.
char a = 'a';
char b = 98;

What about a string? A string is simply a sequence/array/collection of characters. Almost all managed data-type include a built-in data type for string.

Booleans

This allows you to express a binary (yes/no) decision. Boolean data-types can be bool, boolean…

Like characters, internally booleans are numbers. In C, a bool is true when it holds the number 0 for false and 1 or any non-zero number for true.

bool no = false;
bool no2 = 0;
bool yes = true;
bool yes2 = 1;
bool yes3 = 123;

Related

• Data types are how you categorize different kinds of values.
• You should also check out variables.