Just-in-time (JIT) compilation is a technique used to improve the performance of computer programs by compiling parts of the program code at runtime. This is in contrast to traditional compilation, where the entire program code is compiled into machine code before it is executed.

JIT compilation is typically used for interpreted languages, such as Java and JavaScript. In these languages, the source code is first converted into bytecode, which is a more efficient form of the code that can be executed by the interpreter. The bytecode is then compiled into machine code at runtime, just before it is executed.

JIT compilation can improve the performance of interpreted languages by several orders of magnitude. This is because the compiler can take advantage of the specific runtime environment and the current state of the program to generate more efficient code.

JIT compilation is also used for some compiled languages, such as C# and C++. In these languages, the compiler can generate code that is specific to the current runtime environment. This can help to improve the performance of the code, especially for code that is executed frequently.

There are two main types of JIT compilation:

• Static JIT compilation: Static JIT compilation is performed once, when the program is first loaded. This type of JIT compilation is typically used for programs that are not frequently changed.
• Dynamic JIT compilation: Dynamic JIT compilation is performed each time the program is executed. This type of JIT compilation is typically used for programs that are frequently changed or that are executed in a variety of different environments.

JIT compilation can be a complex process, and there are a number of factors that can affect its performance. These factors include the size and complexity of the program, the runtime environment, and the specific implementation of the JIT compiler.

Overall, JIT compilation is a powerful technique that can be used to improve the performance of computer programs. However, it is important to understand the limitations of JIT compilation and to use it appropriately.