A step-by-step guide to C++ function declaration: detailed instructions covering every step

The function declaration tells the compiler the existence of the function without providing a function body. The steps are as follows: Specify the function return type (void if there is no return value) Define the function name Declare the function parameters (optional, including data type and identifier) ​​Add a semicolon

C A step-by-step guide to function declarations: step-by-step explanation

What is a function declaration?

A function declaration informs the compiler of the existence of a function without providing a definition of the function body. It helps the compiler verify the syntax and type correctness of the code before building the program.

Function declaration syntax:

returnType functionName(parameterList);

Where:

• returnType: The data type returned by the function, if it If no value is returned, use void.
• functionName: Identifier of the function.
• parameterList: Optional list of function parameters, their case and data type are required.

Step 1: Specify the return type

First, specify the data type returned by the function, if it does not return any value, use void.

Step 2: Define the function name

Choose a meaningful function name that will identify the function.

Step 3: Declare function parameters (optional)

If the function requires input, declare the function parameters. Each parameter has a data type and an identifier.

Step 4: Add a semicolon

Use a semicolon (;) to end the function declaration.

Practical case:

Let us declare a function named calculateArea that accepts two double parameters and returns a double Type of area:

double calculateArea(double length, double width);

Other notes:

• Even if the function is defined in other files or header files, the function declaration must appear in the place where the function is used in each source file.
• If the function declaration and definition are inconsistent (for example, the return type or parameters are different), the compiler will generate an error.
• Function declarations can appear before or after any other code, but are usually placed before or close to the function definition.

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