A code is a set of instructions that can be understood by a machine. It can be used to instruct the machine to perform an operation or sequence of operations. The code is written in a programming language that the computer understands.
The most common type of code is an executable program, which is a sequence of instructions that tells the computer what to do and how to do it. A program may also contain other types of codes, such as data structures, subroutines and variables.