How to resolve undefined references in C language?

In C language, undefined references typically occur due to missing relevant header files or function definitions. To fix this issue, you can take the following steps:

1. Check if the necessary header files are included in the code. Header files contain information about the declaration and definition of functions, variables, and types. If a reference is undefined, it may be because the related header file is not included. You can use the #include preprocessor directive to include the relevant header files.
2. Ensure that the function is defined or declared. If a function is referenced without being defined or declared, the compiler will not be able to find the function’s implementation, leading to an undefined reference error. Check for the presence of function definitions or declarations in the code, and ensure their correctness and completeness.
3. Check if the compilation options are correct. Sometimes, undefined reference errors may be caused by incorrect compilation options. For example, certain functions may require linking specific library files, and if the linking parameters are not specified correctly, the compiler will not be able to find the implementation of the function. Make sure the compilation options include the correct library files and linking parameters.
4. Check the scope of the variable. If the referenced variable is defined outside the current scope, the compiler will be unable to find the variable’s definition, resulting in an undefined reference error. Make sure the referenced variable is defined within the current scope or properly declared before the reference.
5. Ensure that the names of functions or variables being used are correct. If the spelling of the function or variable name is incorrect, the compiler will not be able to find the definition of that function or variable, resulting in an undefined reference error. Check that the functions or variables referenced in the code are correct and make any necessary corrections.

By following the steps above to check and adjust, the undefined reference error in C language should be resolved. If the issue persists, further analyze error messages or provide specific code examples to better assist in solving the problem.