Difference between Compiler and Assembler

Both compilers and assemblers are the language processors used to convert software codes written in high-level language and assembly language into machine language codes. Compiler and assemblers are the types of system software. These are required because a computer cannot process a code written in high-level programming language like C, C++, Java, etc. and assembly language. Therefore, it is necessary to convert an HLL or assembly code into machine code for execution.

In this article, we will highlight all the key differences between compilers and assemblers. Let's start with some basics of compiler and assembler so that it will become easier to understand their differences.

What is a Compiler?

Compiler is used to translate a high level programming language code to machine level code and to create an executable program. Compiler checks the error in the program and reports them. All errors are to be removed otherwise code will not be compiled and executed.

A compiler takes the sources code as the input and translates it into a machine level language code which is called object code. If there is any syntax or grammatical error in the source code, the compiler records all these errors. A compiler can only convert a source code written in a specific high level language. Each HLL language requires a separate compiler for translation.

Some common examples of compilers are – for Java (JDeveloper, BlueJ, etc.), for C++ (Code Block, GCC, etc.), for Python (JPython, Spyder, etc.).

What is an Assembler?

An assembler is used to translate an assembly level code to machine readable code. Assemblers too check the correctness of each instruction and report the diagnosis report.

In assembly language, the program is written using mnemonics (i.e. abbreviated names assigned to binary codes). The assembler converts these mnemonics into binary code so that CPU of the computer can understand and execute them to perform a task. Therefore, the input program to an assembler is a source code containing mnemonics, while the output is a program containing machine language codes.

Some common examples of assemblers are GAS, MASM, NASM, etc.

Difference between Compiler and Assembler

The following table highlights all the important difference between a Compiler and an Assembler −

Factor Compiler Assembler
Operation Compilers translate high level programming language code to machine level code Assemblers convert the assembly level language to machine level code.
Input Source code in high level programming language. Assembly level code as input.
Conversion type Compilers check and convert the complete code at one time. Assemblers generally do not convert complete code at one time.
Components Lexical analyzer, Syntax analyzer, Semantic analyzer, Code optimizer, Code generator, and Error handler Assemblers work in two passes.
Output Mnemonic version of machine code. Binary version of machine code.
Examples C, C++ , Java compilers. GAS, GNU assemblers.


The most significant difference between a compiler and an assembler is that a compiler converts a high-level language program into a machine level language program, whereas an assembler converts an assembly language program into a machine language program.