C language functions are the basis for code modularization and program building. They consist of declarations (function headers) and definitions (function bodies). C language uses values ??to pass parameters by default, but external variables can also be modified using address pass. Functions can have or have no return value, and the return value type must be consistent with the declaration. Function naming should be clear and easy to understand, using camel or underscore nomenclature. Follow the single responsibility principle and keep the function simplicity to improve maintainability and readability.

C language functions: those bottom lines you must know

Many novices are often confused by functions when learning C language. In fact, functions are not that scary. They are like Lego bricks, the cornerstone of building programs. But to play Lego well, you have to know the rules of building blocks. This article will talk about the basic requirements of C language functions and some of the experiences I have accumulated in my many years of programming career. I hope it can help you avoid detours.

The nature of a function: the modularity of the code

To put it bluntly, a function is to encapsulate a piece of code and give it a name for easy reuse. This is like you wrote a piece of code to calculate the area of ??a circle. You don’t need to copy and paste it every time, just call the function calculate_area(radius) and you can do it. This not only improves the reusability of the code, but also makes the code clearer and easier to maintain. Think about it, if a program with thousands of lines is piled up together, it will be a disaster.

Function skeleton: declaration and definition

A qualified C function must at least have these two parts declared and defined. The declaration is like the ID card of a function, telling the compiler what the name of the function, what type of the parameter is, and what type of the return value is. The definition is the ontology of the function, which contains the specific implementation of the function.

 <code class="c">// 函數(shù)聲明float calculate_area(float radius); // 函數(shù)定義float calculate_area(float radius) { // 計算圓面積的代碼float area = 3.14159 * radius * radius; return area; }</code>

Declarations are usually placed in the header file (.h) and definitions are placed in the source file (.c). This can facilitate modular programming and improve the maintainability and reusability of the code. Remember that declarations and definitions must be consistent, otherwise the compiler will lose his temper.

Parameter pass: value pass and address pass

Parameter passing is another key point in a function. C language uses value passing by default, that is, the function receives a copy of the parameters, not the parameters themselves. Modifying the parameter values ??inside the function will not affect the variables outside the function. But if you want to modify the value of an external variable inside the function, you need to use the address to pass, that is, the pointer to pass the variable.

 <code class="c">// 值傳遞void modify_value(int x) { x = 100; // 不會改變外部變量的值} // 地址傳遞void modify_address(int *x) { *x = 100; // 會改變外部變量的值}</code>

It is very important to understand the difference between value passing and address passing, which is directly related to whether your code is running correctly. Many memory leaks and segfaults are related to errors in parameter passing.

Return value: The output of the function

Functions can have return values ??or no return values. If the function has a return value, be sure to use the return statement in the function body to return a value, and the return value type must be consistent with the function declaration. If there is no return value, void is used as the return value type.

 <code class="c">// 有返回值的函數(shù)int add(int a, int b) { return ab; } // 沒有返回值的函數(shù)void print_hello() { printf("Hello, world!\n"); }</code>

Function naming specification: Clear and easy to understand is the king

Function names should clearly express the function's function, use camel nomenclature or underscore nomenclature to avoid using abbreviations or vague names. A good function name can let you understand the function at a glance, thereby improving the readability of the code.

Experience: Less means more

When writing functions, try to maintain the single responsibility of the function, and each function does only one thing. This can improve the maintainability and testability of the code. If a function's function is too complex, you should consider breaking it into several smaller functions. Remember, the simplicity of code is more important than anything else. This is not only reflected in the number of lines of code, but also in the logical clarity and readability of the code. Complex code, debugging is a nightmare.

In short, when writing C functions well, you need to understand their basic requirements, master the skills of parameter passing and return values, and follow good naming specifications and programming habits. This is not only the basis for writing high-quality code, but also the only way to become a programming master. Practice more and think more, and you can become a C language expert!

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