Read–eval–print loop
A read–eval–print loop (REPL), also termed an interactive toplevel or language shell, is a simple interactive computer programming environment that takes single user inputs, executes them, and returns the result to the user; a program written in a REPL environment is executed piecewise. The term usually refers to programming interfaces similar to the classic Lisp machine interactive environment or to Common Lisp with the SLIME development environment. Common examples include command-line shells and similar environments for programming languages, and the technique is very characteristic of scripting languages, even though their characteristics can vary greatly.