The problem you've presented is a common type of exercise found in many introductory programming textbooks and courses, particularly those focusing on the C programming language and basic data structures. However, without specific details or a unique identifier, it's challenging to pinpoint the exact source or reference book.

Such problems are typically included in materials that cover:

Structs and data types in C$.$

Function declarations and definitions.

File separation $($header files and implementation files$).$

Basic string handling in C$.$

Here are a few common textbooks and resources where similar exercises might be found:

"The C Programming Language" by Brian W$.$ Kernighan and Dennis M$.$ Ritchie $-$ Often referred to as K&R$,$ this book is a classic resource for learning C$.$ It covers all the foundational topics including structs, string handling, and function usage.

$"$C Programming: A Modern Approach" by K$.$ N$.$ King $-$ This book is known for its clear explanations and comprehensive coverage of the C language. It includes numerous exercises similar to the one you described.

"Programming in C$"$ by Stephen G$.$ Kochan $-$ Another well$-$regarded book that offers many practical exercises on using structs and handling strings in C$.$

University Course Materials $-$ Many universities and colleges provide their course materials online, which include exercises similar to the one you've mentioned. These exercises are designed to reinforce concepts taught in lectures and labs.

Online Coding Platforms $-$ Websites like Codecademy, LeetCode, HackerRank, and others often feature exercises for practicing C programming, including struct manipulation and file organization.

If you have access to any of these resources or similar ones, you might find a very similar problem. Otherwise, the problem appears to be a common educational exercise designed to teach and test understanding of basic C programming concepts.