Difference Between Compiler and Assembler

By : Neha Dhyani

Updated : Apr 11, 2022, 11:01

Both compiler and assembler are critical in the context of program execution. The Main Difference Between Compiler and Assembler is that a compiler converts high-level programming language code to machine language code. On the other hand, an assembler generates machine language code from assembly language code.

In this article, let us take a look at the Difference Between Compiler and Assembler.

Compiler Meaning

A compiler converts code written in a high-level language like C++ or Java to lower-level/ machine-level language instructions. The source program refers to the input program. After it is translated into a machine-level language by a compiler, the source program becomes object code.

If the submitted code does not match the rules of its language, a compiler will record all errors. This method is much faster than using an interpreter.

A compiler can only transform source code written in a familiar language. Therefore, each high-level programming language necessitates using a separate compiler for conversion. Also, a computer system may contain numerous compilers to support multiple high-level languages.

Some examples of compilers according to their programming languages are:

  • JDeveloper, Eclipse IDE, BlueJ, etc., for JAVA
  • WebStorm, Komodo Edit, Atom IDE, etc., for JavaScript
  • Code Block, Clang, GCC, etc., for C++
  • JPython, CPython, Spyder, etc., for Python

Assembler Meaning

An assembler is in charge of converting low-level assembly code to relocatable machine code and creating data for the loader. Assembly language code contains mnemonics or symbols/ instructions like ADD, MUX, DIV, SUB, MOV, etc. An assembler translates these mnemonics to binary code.

It generates machine code by evaluating the mnemonics or symbols/ instructions in the operation field and determining the literal and symbol values. An assembler can be a single-pass assembler if it completes all of this work in a single scan. Otherwise, it is a multiple pass assembler.

The input of an assembler or the source program contains assembly language instructions. The assembler produces machine code or object code that computers can understand. Therefore, assemblers are the first interface that allows humans to communicate with machines.

In other words, we need an assembler to bridge the communication gap between humans and machines.

Some examples of assemblers are GAS (GNU Assembler), MASM (Microsoft Macro Assembler), NASM (Netwide Assembler), etc.

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Difference Between Compiler and Assembler

Below are the major Difference Between Compiler and Assembler:





Source code to “machine-level language.”

Assembly codes to machine codes


High-level language codes

Low-level assembly language code


“Mnemonic” form of a machine code

Binary codes

Number of operations

Single operation

Multiple operations


More efficient and intelligent

Less efficient and intelligent

Number of phases

The compiler works in six phases. Each converts the original program into a new format. They are:

1.     Lexical analysis

2.     Syntax analysis

3.     Semantic analysis

4.     Intermediate code generator

5.     Code optimizer

6.     Code generator

Each stage receives input from the previous one and outputs to the next.

Assemblers generate machine code in two phases: pass 1 and pass 2.

A compiler converts the source code to machine language. It translates sophisticated codes into a machine-readable format. In addition to that, the compiler combines all the program instructions into a single line of code. Before execution, the compiler often removes errors from the source code.

In contrast, the assembler translates assembly codes to machine codes. It converts the core commands of assembly codes into binary code that a processor can understand.

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FAQs on Difference Between Compiler and Assembler

Q.1. What is the Main Difference Between Compiler and Assembler?

The Main Difference Between Compiler and Assembler is that a compiler converts high-level programming codes to machine-level language, whereas an assembler converts low-level assembly language codes to machine codes.

Q.2. What is the Difference Between Compiler and Assembler regarding time efficiency?

The Difference Between Compiler and Assembler regarding time efficiency is that the compiler takes more time than the assembler as it takes time to break down complex programming codes into low-level machine language.

Q.3. What is the Difference Between Compiler and Assembler concerning their types?

The Difference Between Compiler and Assembler concerning their types is the following: Compilers have three types - one-pass, two-pass and multi-pass. There are other types of compilers like cross, load-and-go, threaded, just-in-time, parallelizing, incremental, etc.

On the other hand, assemblers have two types - one-pass and two-pass.

Q.4. What is the Difference Between Compiler and Assembler regarding the ease of debugging?

Debugging is spotting and correcting bugs in computer programs, software, or systems. The Difference Between Compiler and Assembler regarding ease of debugging is that whereas debugging is easy in compilers, it is difficult to debug in assemblers.