Bytecode and machine code are two important representations of a program during execution. They differ mainly in their level, execution method, and platform dependency.
Byte Code
Bytecode is an intermediate, platform-independent code generated after compiling source code. It is executed by a virtual machine like JVM instead of directly by the CPU.
- Executed by JVM using interpreter or JIT compiler
- Platform-independent and portable
Machine Code
Machine code is the lowest-level code consisting of binary instructions that are directly executed by the CPU. It is specific to a system’s architecture.
- Directly executed by CPU without any virtual machine
- Platform-dependent and hardware-specific
The below figure illustrates the example of how Java source code is converted to Byte code and then to machine code :
Byte Code vs Machine Code
| Byte Code | Machine Code |
|---|---|
| Intermediate-level code generated after compilation | Lowest-level code executed by CPU |
| Executed by a virtual machine (JVM) | Executed directly by CPU |
| Not directly understandable by CPU | Directly understandable by CPU |
| Platform-independent | Platform-dependent |
| Less machine-specific | Highly machine-specific |
| Uses interpreter and JIT for execution | Does not require any virtual machine |
| Portable across systems with JVM | Specific to system architecture |