The Arduino software is an open-source and easy to use platform which configures the Arduino board into functioning in a certain way. An Arduino code is written in C++ but with additional functions and methods. An Arduino is a hardware and software platform widely used in electronics.

In this article, we will see a few quick fixes for the error ‘does not name a type‘ or the ‘no such file or directory‘ error.

Also read: How to stop an Arduino program?

What does the error mean?

In almost every coding language known to man, every variable has a specific data type. In general, there are multiple data types like int indicating integer, float for decimal values, char and String for alphabets and sentences, boolean for true or false and many more. In Arduino, there are 16 data types commonly used.

void: Used in function declarations, and indicates that the function will not return anything.
boolean: It is a true or false value.
char: Stores a character value in one byte of the memory.
Unsigned char: Unsigned data type which encodes numbers between 0 and 255 and occupies one byte of the memory.
byte: It is an 8-bit unsigned number holding a value between 0 and 255.
int: It is a primary data type which stores a 16-bit integer value. It can store negative values.
Unsigned int: Unsigned integer that stores only positive integer values in the 2 byte memory.
long: It is a 32-bit memory for storing numbers, both positive and negative.
Unsigned long: Unsigned long variables store only positive numbers in the 32-bit memory storage.
short: It is a 16-bit data type storing positive and negative numbers.
float: It is a decimal value having a 32-bit memory.
double: It is a double floating number having either 32 or 64 bit memory depending on the board.
word: Based on the type of board, it stores either 16-bit or 32-bit unsigned number.
array: It is a collection of variables which is accessible using index numbers.
String-char array: Converts the string into an array of characters.
String-object: Class which can be used to manipulate, concatenate and perform other operations on strings and arrays.

The error ‘does not name a type‘ or the ‘no such file or directory‘ are errors that occur during the compilation process. They generally indicate missing data types or wrongly used data types. It may also indicate missing directories or libraries.

How to fix ‘does not name a type’ in Arduino?

Here are two ways to fix the error.

Check data type

Every user-defined function and variable initialised or declared in the code should have a corresponding data type. The data type of the variable or function should also coincide with the value being stored or returned.

Consider a small example sample code below.

What is 'does not name a type' in Arduino: 2 Fixes

Here the function MQRead is of the type float. The variables i and mq_pin are integer type, while rs is float type. In the for loop, i is given the value 0, an integer value. The analogRead function always reads an integer value, which is being assigned to the mq_pin variable. Since the value or type for rs, the float type suffices for any value assigned to it as a result of the calculation. The user-defined function MQRead is of type float, which means that the return type for it is float, which is achieved by returning the value of rs for the function.

The error occurs if any of these data types don’t stand to the data being stored in the variables. Always check and recheck the data type for every variable, function and return type.

Library folder

In many cases, you may use libraries that are not standard or included in Arduino. But Arduino is flexible with the import of new libraries, making it easy to use all functions from any library. Follow the path below to check the currently available libraries in your Arduino software.

My Documents -> Arduino -> Libraries

Consider the snippet of code below. There are four library folders that are included for the code to work. But these aren’t a part of the standard library of Arduino.

There are two ways to import a library to the Arduino.

Method 1

Step 1: Click on Sketch on the top left panel of the window. Go to the include Library option and select Manage Libraries.

Keyboard Shortcut: Ctrl+Shift+I.

Step 2: Search or select from the options available and click on Install.

Note that a few Libraries may not be available if your software isn’t updated with the latest version.

All the libraries you are planning to use may not be easily found under the Manage Libraries section. In such cases, we use Method 2 for importing the libraries.