Difference Between Compiler and Assembler

By BYJU'S Exam Prep

Updated on: October 17th, 2023

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

We need an assembler to bridge the communication gap between humans and machines. 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. This article will look at the difference between a Compiler and an Assembler on various factors and briefly explore each.

Difference Between Compiler and Assembler

The main difference between a compiler and an assembler is that there are 6 phases in the compiler, whereas there are only 2 phases in the assembler. Both compiler and assembler are important as per the GATE CSE exam. Let us understand the comparison between the two in detail in the table provided below.

Compiler vs. Assembler

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:

  • Lexical analysis
  • Syntax analysis
  • Semantic analysis
  • Intermediate code generator
  • Code optimizer
  • Code generator

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

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

Compiler and Assembler

A compiler converts the source code to machine language. It translates sophisticated codes into a machine-readable format. In addition, 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.

What is a Compiler?

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.

A compiler can only transform source code written in a familiar language. These languages are mentioned in the GATE CSE syllabus. 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

What is an Assembler?

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 operation field’s mnemonics or symbols/ instructions 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.

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

Other Important GATE Topics
Difference Between System Software and Application Software Difference Between HTTP and HTTPS
Difference Between Malware and Virus Gear Profiles
Difference Between SRAM and DRAM Difference Between AMD and Intel
Our Apps Playstore
SSC and Bank
Other Exams
GradeStack Learning Pvt. Ltd.Windsor IT Park, Tower - A, 2nd Floor, Sector 125, Noida, Uttar Pradesh 201303
Home Practice Test Series Premium