What is Just-in-Time Compiler?
JIT Compiler
It is a compiler component that translates software code into machine language on-the-fly as the program runs, thereby improving performance.
Overview
A Just-in-Time Compiler is a software mechanism that converts source code or intermediate code into machine code during program execution. Unlike traditional ahead-of-time compilation methods, rather than translating the entire code upfront, it processes the needed parts at runtime. Thus, it ensures both a fast startup time and high runtime performance. It is frequently preferred in modern virtual machines and interpreted languages.
How it works
When the program starts running, the code is first interpreted at the bytecode level. When frequently executed and performance-critical code blocks are detected, this component comes into play. It converts the relevant blocks directly into machine instructions that the processor can understand and stores them in memory to execute them quickly on subsequent calls.
Where it is used
It is widely used in Java Virtual Machine, .NET Common Language Runtime, and JavaScript engines in modern web browsers.
Commonly confused with
Unlike the concept of JIT compilation, which is the runtime compilation action itself, it refers to the concrete software engine that performs this process.
Questions and answers
Why does a JIT compiler speed up the program?
Because it translates frequently repeated code snippets into machine code and caches them, eliminating the need to re-interpret the code every time.
What is the difference from AOT compilers?
While AOT compilers completely convert code into machine language before the program runs, this component compiles dynamically while the code is running.
Related terms
This explanation was written in plain language for TreScout with AI and machine-translated from the Turkish original · the Turkish version prevails. If something looks wrong or missing, write to hello@trescout.com. Read in Turkish →