1.) A button on a keyboard.
2.) In database management systems, a key is a field used to sort data. It can also be called a key field, sort key, index, or keyword. For example, if you sort records by age, then the age field is a key. Most database management systems allow you to have more than one key to sort records in different ways. One of the keys is designated the primary key and must hold a unique value for each record. A key field that identifies records in a different table is called a foreign key.
3.) In cryptography, an encryption key is a string of characters used in combination with an algorithm (a cipher) to transform plaintext into ciphertext and vice versa for decryption algorithms. An encryption key is used to encrypt, decrypt, or carry out both functions based on the encryption software used. The longer a key is built, the harder it is to crack the encryption code.
4.) A password or table needed to decipher encoded data.
5.) Memory keys are physical notches on the module that prevent the memory from being incorrectly installed in a computer system. Memory keys also prevent the memory from being installed into an incompatible computer system.
