How can the C language program achieve high readability, easy maintainability and extensibility

I. Top-Down Design

Overall Planning

Starting from the overall function of the program, define the main module (such as the main() function) first, and clarify the overall goal and input/output of the program. For example, when designing a student management system, first determine the top-level functional modules such as "data entry", "query", and "statistics" that need to be implemented.

Step-by-step decomposition

Break down complex problems layer by layer into sub-problems to form a tree-like structure. For example, "data entry" can be further divided into sub-modules such as "input student information", "validate data format", and "store to file". Each sub-module is further decomposed until each task is simple enough (typically corresponding to a function within 50 lines). 。

Hierarchical design

The hierarchical structure is reflected through the function call relationship. The top-level module calls the lower-level module, and the lower-level module does not depend on the upper-level module in the reverse direction.

II. Structured Programming

Control Structure Restrictions

Only use the three basic structures: sequence, selection (if/switch), and loop (for/while). Avoid using the goto statement. For example, use a for loop to replace complex jump logic. \
\
Single entry, single exit

Each function or code block has only one entry and one exit to ensure clear logic. 。 For example, in a function, avoid multiple return statements and uniformly return the result at the end. \
\
Code block normalization

Clarify the boundaries of code blocks through indentation, alignment of parentheses, etc., to enhance readability. For example:

   if (condition) {  
       // Code block  
   } else {  
       // Code block  
   }

III. Modular Programming

\
Functional Module Division

Divide the program into independent functional units, with each module corresponding to a function or a group of related functions. For example:

The main module: main() is responsible for process control.
Functional modules: such as input_data(), calculate_score(), etc.
Tool modules: such as file_io.c for handling file operations.

Separation of interface and implementation.

Header file (.h): Declare function prototypes, data structures, and define interfaces. For example:

     // file_io.h  
     int read_file(const char* filename);

Source (.c) : Implements the specific functionality, hiding the internal details

     // file_io.c  
     #include "file_io.h"  
     int read_file(const char* filename) { /* Implementation */ }

Module independence principle

High cohesion: Functions within modules are closely related (e.g., all mathematical calculations are centralized in math_utils.c)
Low coupling: Modules pass data through parameters, avoiding global variables . For example, using function arguments instead of external variables to pass the result of a computation.

Module integration and testing

The main module is integrated and debugged step by step by including header files to call each sub-module . For example:

   #include "file_io.h"  
   #include "data_process.h"  
   int main() {  
       read_file("data.txt");  
       process_data();  
       return 0;  
   }

Ⅳ.Practical Examples

Take the "Student Performance Statistics Procedure" as an example:

Top-down design: the main function calls input_scores(), calculate_avg(), and output_result().
Structured encoding: Only three control structures are used inside each function, such as a for loop over an array of grades.
Modular implementation: io_module.h/c: Handles input and output calc_module.h/c: Implements statistical logic The main program integrates modules through header files .

V. Precautions

Code size control: A single function is recommended to be no more than 50 lines, and complex logic is split into subfunctions .
Naming conventions: Function names should be explicit (e.g., validate_input(), not func1()).
Documentation comments: The header should state the module functionality and interface parameters .

Through the above methods, the C language program can achieve high readability, easy maintainability and extensibility, which is in line with the core goal of structured programming .

DEV Community