Question

Are the following MATLAB variable names legal or illegal? Why? a. dog1 b. \(1 \mathrm{dog}\) c. Do you_know_the_way_to_san_jose d. help e. What's_up?

Short answer

a. Legal (follows all rules) b. Illegal (starts with special character, contains special characters & spaces) c. Illegal (contains space) d. Illegal (built-in function name) e. Illegal (contains special characters)

Step-by-step solution

Check variable name: dog1

The variable name 'dog1' begins with a letter, contains no spaces or special characters, and is not a reserved keyword. Therefore, it's a legal MATLAB variable name.

Check variable name: \(1 \mathrm{dog}\)

The variable name '\(1 \mathrm{dog}\)' begins with a special character, which violates rule 1. Also, it contains special characters and spaces, which are not allowed. Therefore, it's an illegal MATLAB variable name.

Check variable name: Do you_know_the_way_to_san_jose

The variable name 'Do you_know_the_way_to_san_jose' begins with a letter, but it contains a space, which is not allowed. Therefore, it's an illegal MATLAB variable name.

Check variable name: help

The variable name 'help' begins with a letter, contains no spaces or special characters, but it's a built-in function in MATLAB. As per rule 4, it's not allowed to use built-in function names as variable names. Therefore, it's an illegal MATLAB variable name.

Check variable name: What's_up?

The variable name 'What's_up?' begins with a letter, but it contains special characters (' and ?), which are not allowed. Therefore, it's an illegal MATLAB variable name.

Key concepts

Programming for Engineers

Engineering students and professionals often find themselves needing to program applications, simulations, or analyses to solve complex problems. MATLAB, standing for Matrix Laboratory, is a high-level programming language and environment specifically designed for these tasks. It offers a blend of simplicity and power that enables engineers to perform mathematical computations, data analysis, and algorithm development efficiently.

When you're diving into programming with MATLAB, the first step is understanding how to name your variables, as they are the building blocks of your code. Correct naming allows your code to be readable, maintainable, and free from unexpected errors. Remember, the main goal is to create a variable name that encapsulates its use, making your code intuitive to fellow programmers and your future self.

Legal Versus Illegal Identifiers

MATLAB, like many programming languages, follows specific rules for naming variables (otherwise known as identifiers). This is essential for the language to be able to distinguish variable names from other elements of the code. A legal identifier starts with a letter, which can be followed by letters, digits, or underscores. They are case sensitive, meaning 'myVar' and 'MyVar' would be considered different variables.

In contrast, illegal identifiers contain spaces, start with a number or special character, include other special characters, or use MATLAB reserved words, such as the names of built-in functions. For example, 'dog1' is legal, but '1dog' and 'What's_up?' are not because they start with a number and contain a special character, respectively. By adhering to these naming conventions, you prevent syntax errors and ensure that your code communicates clearly its intent.

MATLAB Syntax Rules

MATLAB's syntax rules set the foundation for writing executable code. These rules govern the structure of the code, including how variables are named, how functions are called, and how operations are executed. Some cardinal rules include starting variable names with a letter, avoiding MATLAB's reserved keywords as variable names, and not using special characters or spaces within names.

For instance, the variable name 'help' is not allowable because 'help' is a function in MATLAB, and using it as a variable could confuse the compiler and the human reader. Similarly, 'Do you_know_the_way_to_san_jose', despite starting with a letter, is illegal due to the presence of spaces. Following the syntax rules not only ensures that your code runs without a hitch but also upholds the standards for writing clean, readable, and professional code.