Worked on the unicode-org/icu repository to enhance the clarity and accuracy of technical documentation, focusing on the behavior of the U_stdio module in C. Updated the documentation for the u_fgetc function to specify that ill-formed characters are represented by the replacement character U+FFFD, correcting a previous inaccuracy that stated U+FFFFFFFF. This change ensures that the documentation now aligns with the actual runtime semantics, improving maintainability for future contributors. The work demonstrated attention to detail in documentation practices and a commitment to codebase quality, utilizing skills in C and technical writing to deliver precise and reliable reference materials.