A hash code is a numeric value that is generated by a hash function. It is used to uniquely identify data or objects. Hash functions take in input of variable length and produce an output of fixed length, which is the hash code. The primary purpose of a hash code is to quickly retrieve or identify data in various data structures such as hash tables, sets, or maps. Hash codes are used to index and organize data so that it can be accessed efficiently. Hash codes are commonly used in programming languages and frameworks for tasks like indexing data structures, implementing caching mechanisms, and ensuring data integrity. For example, in Java, the hashCode() method is implemented by many classes to provide a unique identifier for objects. It's important to note that while hash codes should ideally be unique for different objects, collisions can occur where two different inputs generate the same hash code. In such cases, additional mechanisms like separate chaining or open addressing are used to handle collisions and maintain data integrity. Overall, hash codes play a crucial role in efficient retrieval and identification of data within various algorithms and data structures.