Computer code or program code is the set of instructions forming a computer program which is executed by a computer. It is one of two components of the software which runs on computer hardware, the other being the data.
Computers can only execute the machine code instructions which are part of their instruction set. Because these instructions are difficult for humans to read, and writing good programs in machine code or other low-level programming languages is a time-consuming task, most programmers write in the source code of a high-level programming language. This source code is translated into machine code by a compiler or interpreter so that the computer can execute it to perform its tasks. A compiler produces object code which is usually in machine language but may also be in an intermediate language which is at a lower level than the source. A runtime system is often used to execute object code by linking it with commonly used libraries. Bytecode is a lower level of source which is designed for more efficient interpretation by interpreters.