Every computer is associated with a set of instructions that is recognized and executed by that computer itself. The instructions are stored as binary bit patters, as strings of 1s and 0s. So any particular computer can only execute instructions in the machine code langue of its microprocessor. The program can be stored on a disk and then loaded into the computer’s internal memory, and then the instructions are fetched one by one by the CPU and executed. Previously, programmers used to write programs in the native machine code of the processor, but the whole process was time-consuming and expensive, and the machine code is of no use to a human reader.

To overcome these problems, assembler language was invented. In this, data can be represented using decimal numbers instead of binary. But a program is required to convert an assembler language program into machine code. This program is called an assembler. Assemblers made programs human readable and programming less error-prone, but could not overcome the portability problem. The shortcomings in the assembler programs led to the development of high-level programming languages which made programming more productive, but again, they could not be executed on a computer. A compiler is then used for this purpose. And to make the same compiled program run on any computer, the program is compiled to something called bytecode.

What is Bytecode?

Bytecode is a highly optimized set of instructions designed to be executed by a program, usually referred to as a virtual machine. It is an intermediate code compiled into a low-level code from the source code for efficient execution by a software interpreter. It is essential to recognize that Bytecode is not machine code used by the hardware processor. The virtual machine converts bytecode into specific machine instructions that the computer’s processor will understand. A just-in-time compiler can be used as a means to speed up execution of bytecode. In Java, a bytecode is the instruction set for the Java Virtual Machine (JVM). The JVM is a program that provides the runtime environment necessary for the execution of Java programs. The programs cannot run unless there is a JVM available for the appropriate hardware and OS platform you will execute on. The JVM is an interpreter for bytecode. Java bytecode is not platform-specific, so it can be fed to just any platform.

What is Machine Code?

Machine code is a computer program that is made up of the native instructions associated with that particular computer. It is the elemental language of computers written in machine language instructions consisting of binary or hexadecimal instructions that is directly understandable by a computer’s central processing unit (CPU). Every computer processor is associated with a set of machine code instructions which it can understand and therefore execute. All the programs must be converted into the machine language before they can be run. A compiler converts the program written by a computer programmer into machine code containing 0’s and 1’s, and the OS then runs the application in machine code. It simply is a list of CPU instructions stored in memory at the lowest level. Compilers convert high-level languages such as C, C++ and Java to an intermediate language (such as bytecode) which is then interpreted to machine language.

Difference between Bytecode and Machine Code

Definition

 – Bytecode is an intermediate code compiled into a low-level code from the source code and designed to run on a virtual machine instead of a central processing unit (CPU). It is a highly optimized set of instructions which can be recognized as a machine code for a made-up processor or a machine code for the CPU of the internal computer. Machine code, on the other hand, is a computer program made up of the native instructions consisting of a stream of 0’s and 1’s that can be directly executed by a computer’s CPU.

Function

 – Bytecode is similar to machine code which is interpreted by a runtime system so that the code can be executed on a system. The virtual machine converts bytecode into specific machine instructions that the computer’s processor will understand. The function of a bytecode is to be a format that can be executed efficiently by the virtual machine’s interpreter. Machine code is the elemental language of computers written in binary or hexadecimal that is understandable by a computer’s CPU. It is the language which all programs must be converted into before they can be run.

Platform

 – Bytecode is platform-independent because it can be executed on any platform using the virtual machine. The format of bytecode is always the same, regardless of what type of machine it was created on. A program can be compiled into bytecode and sent to any machine, if that machine has the run-time installed. Machine code, on the other hand, is not platform independent meaning it cannot be run on just any platform with the same OS because it is made up of the native instructions associated with that particular computer.

Bytecode vs. Machine Code: Comparison Chart

Summary

Bytecode is not a machine code for any particular computer and may be portable among computer architectures. It is similar to machine code which is interpreted by a runtime system so that the code can be executed on a system. The virtual machine converts bytecode into specific machine instructions that the computer’s processor will understand. Machine code is a computer program that can be executed directly by the computer’s hardware with no software needed. Unlike bytecode which is platform-independent, machine code cannot be run on just any platform with the same operating system.

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