In computer science, compile time (or compile-time) describes the time window during which a computer program is compiled.The term is used as an adjective to describe concepts related to the context of program compilation, as opposed to concepts related to the context of program execution (runtime).For example, compile-time requirements are programming language requirements that must be met by source code before compilation and compile-time properties are properties of the program that can be reasoned about during compilation.The actual length of time it takes to compile a program is usually referred to as compilation time.