Constants in Arduino

Constants in Arduino
Constants in Arduino

Constants in Arduino In any programming language, data is crucial for programmers. We must be careful about the data we use and its format while writing programs. For instance, if we have a variable that stores someone’s age, storing it in text format like “thirty years old” would be nonsensical to the application and create issues. We’d rather store the person’s age as a number, like 30. However, all computer languages employ constant values to allow repeated calculation. These constants will dominate this book for the next few chapters.

Hi there! When you first started coding, you probably encountered constants. What are they? You need them why? Don’t worry—we’ve all been there. I’ll discuss the LED_BUILTIN constant and logical and pin constants in this beginner’s guide. With some easy examples and clear explanations for beginners, you’ll understand constants quickly. You’re in the right place if you’re building your first Arduino or learning about code. Stick with me and you’ll talk constants like an experienced coder soon!

Definition of Constants

Expressions having fixed values are constants. Normal program execution cannot change the value. Changing a constant would cause a compilation error. Every constant is data-typed. Examples include 9E-15 (natural helium availability) and 3.1416 (rational pi number). 450, 64, and 3E8 are not constants since they lack data types. The keyword final indicates that the constant value cannot be modified. Every class could have constants. However, declaring numerous comparable constants in one class is bad programming.

The keyword static is better for grouping such constants. A static field belongs to the class, not an object. Thus, a static field has only one copy, regardless of how many class objects are produced. Alternatively, a class may have several instances, each with its own instance fields. One copy of a static field exists. This is static field principle. Each instance of a class with an instance field has its own copy. This is instance field principle.

Types of Constants

Well, the constant values cannot change during program execution. This indicates that constant performs a specific computer activity and helps you avoid assigning that value to a variable. Literals are C programming constants. Two types of C constants exist. These are: Main Constants. Directly expressed constants can be the following types: An integer constant is a full number without fractions. Real: Real constants are fractions or decimals. Single Character: A single-character constant uses single or double inverted commas. The primary constants include the aforementioned special kinds, but they must be in the prior list. An integer cannot have a sign, and there is no long or short integer indicator like in C++. These are absent from C.

If needed, primary constants can have integer- and long-suffixes. Secondary Constants: Using unsaturated formula fundamental constants, this constant is determined. If we multiply 9*5+2 by 45, for example. I can assign a constant integer equal to 9*5, or 45. Use that constant in the new constant expression. Secondary constants are needed in larger software programs when formulae or primary constant changes influence several components. These constants are crucial to symbolic manipulation program routines. On their own line, utilize meaningful constant names to improve program comprehension inside the routine’s context. The same program can be tweaked more easily if needed. Only use the detailed outcome for “section 1.2.”

Programming Constants Matter

How significant constants are in programming is hard to quantify. The uniqueness of constants in each programming discipline shows their relevance. However, constants’ importance in programming depends on the user’s goals, programming language, and use. Programmers utilize constants to help users grasp program logic, especially when reading the program. Because the constant value or number’s meaning is assigned once, it cannot be modified during program execution. Thus, “final double PI = 3.14;” indicates that PI is a constant whose value is fixed to 3.14 and is not expected to change. PI is allocated a data type double as a whole number to store it once as a constant and prevent manipulation. Programming constants provide modularization between program portions. It’s defined and accentuated.

What are coding constants?

Code-defined constants cannot be modified. They’re handy for mathematical constants, API keys, and configuration parameters that don’t change each time the program runs.

Define Constants

The const keyword defines constants in most languages. A C++ example:

double PI3.14;

This maintains PI at 3.14. The value of PI cannot be changed once defined.

Python modules define constants with all-uppercase names:

PI = 3.14

Using Constants

Code uses constants instead of “magic numbers” or hardcoded values. This improves code readability and maintainability. As an example:

circumference = 2*PI*radius

reads better than:

2 * 3.14 * radius = circumference

Normal Constants

Common code constants include:

Math constants: PI, GRAVITY, E

Keys and credentials for API


Status_OK, Error_NOT_FOUND are magic numbers.

Clear constant names improve code documentation and maintainability. Clean, readable code relies on them.

Genuine Constants

Numbers, strings, and booleans are literal constants in your code. As an example:

Constants: age = 30, name = “John”, is_valid = True.

These values will not change throughout program execution.

Symbolic constants are variables with a fixed value and a name. As an example:

PI = 3.14 # pi constant

When you use PI in code, it now represents 3.14. Readability is the main benefit of symbolic constants—PI is more meaningful than 3.14.

A List of Constants

Enums are named constants. As an example:

Color class: RED = 1 GREEN = 2 BLUE = 3

You can now use Color.RED, Color.GREEN, and Color.BLUE in your code. You can type-safely represent a fixed collection of values with enums.

Learn about constant types to use them effectively in your code. Constants improve program readability, maintainability, and bug-freeness.

Explaining Logical Level Constants

Logical level constants are compiler-defined programming language constants. Their meaning and value are set.

Truth and falsity
In boolean logic, TRUE and FALSE signify true and false. TRUE = 1 in C, FALSE = 0.


A NULL pointer points to nothing. Its value is 0. Using NULL to initialize a pointer variable without an item to point to.


The CHAR_BIT constant indicates char bit count. In C, CHAR_BIT is 8, therefore a char is 1 byte. C++’s CHAR_BIT is 8 bits for ASCII and 16 bits for Unicode.


INT_MAX and INT_MIN are int’s maximum and minimum values. In C, INT_MAX is 32767 and INT_MIN is -32768. These values depend on the compiler, machine architecture, and int bit count.

Understand logical level constants to develop more portable and optimized programs. They can establish data type sizes, initialize pointers, represent booleans, and more. Many languages contain preset constants; use them in your programs!

You’ll write cleaner, more streamlined code quickly once you understand logical level constants. Have more questions? Let me know!

LED_BUILTIN Example with Pin Level Constants

To represent hardware components, microcontrollers use different constants. Pin level constants represent microcontroller input and output pins.

These constants make it easy to reference a pin in code without remembering the number. Pin 13 of an Arduino Uno connects to an LED. The LED_BUILTIN constant can replace remembering that the LED is attached to pin 13.

Thus, instead:

pinMode(13, OUTPUT); digitalWrite(13, HIGH);

You can use constant:

digitalWrite(LED_BUILTIN, HIGH);

Constants Improve Code Readability

Use variables like LED_BUILTIN to simplify your code for yourself and other developers. Instead of checking pin 13, the code clearly interacts with the built-in LED.

Constants are named in uppercase letters at the start of a drawing, outside of functions: const LED_BUILTIN = 13;

Once specified, the constant can replace the pin number throughout the drawing. If you change the LED’s pin, you simply need to update the constant definition; all other references will use the new pin.

A best practice for modular and scalable C/C++ code is constants. Pin level constants abstract hardware-specific characteristics, making microcontroller code portable across boards.

Advantages of Constants

Constants have several advantages in code:

Stops inadvertent changes. Making a variable constant prevents errors by prohibiting value changes.

Code that documents itself. Names for constants commonly use uppercase letters and underscores. This convention makes the constant’s purpose clear to code readers.

Simpler refactors. If you need to alter a constant value in your code, you simply need to change it where it’s specified. All other usages update automatically.

Common Constant Uses
Common constant uses include:

Set configuration values. Take “abc123” as an API key.

The pin numbers or I/O mapping on embedded devices. Example: const LED_PIN = 13;

Defining meaningful numbers. Example: const MAX_BATCH_SIZE = 100;

Strategically using constants in code makes programs more robust, readable, and maintainable. They are essential to developing clean, well-designed code in any language.


That’s it! Constants may seem mysterious, but they’re only tools for code readability and reuse. Constants clean up code, whether they’re logical constants for pin states, pin constants for pins, or built-in constants for LEDs. Learn Arduino and discover new constants that capture common values you require again and again. They’re not complicated, so don’t be afraid of them. Friend constants! Use them liberally to write clear, enjoyable code.

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