A hash function is a mathematical function that takes in an input (or "message") and returns a fixed-size string of characters, which is typically a hexadecimal or binary representation. The output, known as the hash value or digest, is unique to the input data, meaning even a small change in the input will produce a significantly different hash value. Hash functions are commonly used in computer science and cryptography for tasks such as data integrity checks, password storage, digital signatures, and data indexing. # Hash Function and Hash Table Hash functions and hash tables are tightly connected. A hash function is a function that takes an input (or key) and generates a fixed-size value, known as a hash code or hash value. This hash code is typically used as an index to access data in a hash table. A hash table, also known as a hash map, is a data structure that uses a hash function to map keys to values. It typically consists of an array of fixed-size buckets or slots, where each bucket can store one or more key-value pairs. The hash function determines which bucket each key should be placed in. When inserting or retrieving data from a hash table, the same hash function used during insertion is used to compute the index of the corresponding bucket. This allows for efficient retrieval of data based on its key, as the search can be narrowed down to the specific bucket using the computed index. In summary, a hash function is used to generate an index for storing and accessing data in a hash table. # References ```dataview Table title as Title, authors as Authors where contains(subject, "hash") or contains(subject, "Hashing") ```