The C programming language is a strongly typed language, meaning data structures and variables must be declared in advance. As such, the compiler is able to enforce proper usage of these declared types and catch a variety of bugs at compile-time.
Additionally, the language supports the concept of structures which are user-defined data types that can be used to encapsulate data and code in a modular fashion. These modules can be written individually and combined to form a more complex and larger program. This divided structure improves the efficiency of testing by making it extremely easy to evaluate defects, remove them and maintain the program.