Difference Between Assembler and Interpreter

Assembler and Interpreter, both are system programs that perform language translation. They accept a computer program in one language and convert it to another language. Although they are quite different in their working process.

Assembler is a system program that accepts assembly language code and converts it to machine language code. On the other hand, the interpreter accepts the source code in a high-level language and translates it into machine language code.
In the case of an assembler, before execution, the source code has to pass through translation, linking and loading. However, in the case of an interpreter, the source code is directly translated.

In the section ahead, we will explore more differences between these two language translators.

Content: Assembler Vs Interpreter

1. Comparison Chart
2. What is Assembler in Computer?
   • What is Assembler Language
   • How Does Assembler Work?
   • Types of Assembler
   • Assembler Directives
3. What is Interpreter in Computer?
   • How Does Interpreter Work?
   • Types of Interpreter
4. Similarity Between Assembler and Interpreter
5. Key Differences
6. Conclusion

Comparison Chart

Basis for Comparison	Assembler	Interpreter
Basic	It accepts assembly language code and converts it to a relocatable machine language code.	It translates source code in a high-level language to machine language, instruction by instruction.
Input	Low language program (assembly language code)	High-level language program
Translation	Translation takes place before program execution.	Translation takes place at the time of execution.
Errors	It identifies errors before program execution.	It identifies errors at the time of execution.
Executable File	It creates an executable file.	It does not create any executable file.
Use Source Code	It uses source code once to create an executable file	It uses source code each time during the execution
Memory Requirement	It requires comparatively more memory.	Less memory
Speed	Faster	Slower

What is Assembler in Computer?

Assembler is a system program that translates the assembly language code into a relocatable machine code. The Assembly language code that it accepts is a low-level language code. Though it is close to machine language code, still the system is unable to understand this assembly language code.

Thus, we need an assembler to convert assembly language code to machine language code. During translation, the assembler does not resolve all the external references in the assembly code. These references are later resolved by the linker. So, the assembler is quite fast in translation.

The assembler generates a machine language code in an executable file. Thus it requires memory for the storage of this executable file.

How Does Assembler Work?

The working of an assembler totally depends on how many phases it will be used to convert assembly language code to machine language code.

If it’s a one-pass assembler, it would resolve all the instructions in a single pass and would generate the machine code.

If it’s a two/multi-pass assembler, it will resolve all the instructions in code in two or multiple passes.

Types of Assembler

One-pass Assembler

The one-pass assembler converts the assembly language program to a machine language program in a single pass.

Two/Multi-Pass Assembler

The two-pass assembler converts assembly language code to machine language code in two or multiple passes.

• In the first pass, the assembler processes the pseudo-op instructions, identify symbols and opcodes and stores them in the symbol tables.
• In the second pass, the assembler converts the opcode into a numeric opcode, resolves the pseudo opcode and generates machine code.

Assembler Directives

Assembler directives are the commands that control the operation of the assembler. These commands basically help the assembler in the:

• Identifying the beginning and end of the program
• Assigning storage to the data
• Assigning values to the variables
• Identify the start and end of different segments, macros, procedures etc.

What is Interpreter in Computer?

The interpreter is a language translator that translates a source code in a high-level language to a machine language code. During this translation, the interpreter does not generate any intermediate program. We refer to this intermediate program as the target program. So, compared to other language translators, it takes less memory for storage.

The interpreter line-by-line scans the instructions from the source program and translates them to the machine instruction. Thus, it detects errors in the source program at the time of execution. Error debugging is easier with an interpreter.

The interpreter resolves all the external references in the source code during interpretation. Thus, it is slower.

How Does Interpreter Work?

The interpreter interprets the source program using the interpretation cycle repeatedly. The interpretation cycle analyzes the first statement of the source program, understands its meaning and then performs the corresponding action.

Now in each interpretation cycle, the interpreter analyzes the next statement of the source program, identifies its meaning and performs the corresponding action. The interpreter even resolves the external references during translation. All this incurs substantial overhead on the interpreter making it slow.

The interpreter does not even produce any target program like a compiler or assembler. Thus it requires less memory as compared to other language translators.

Types of Interpreter

• Bytecode Interpreter
  The compiler first compiles the source code and converts it into bytecode. Bytecode is not exactly machine code, but it is a compressed and optimized source code form. This bytecode is then interpreted by the interpreter and converted to the machine code. As here we require both compiler and interpreter, we often refer to bytecode interpreters as “compreters”.
• Threaded Code Interpreter
  Threaded code is a technique that we use to implement virtual machine interpreters. It is similar to a bytecode interpreter but uses pointers to access functions or instructions n the source code.
• Abstract Syntax Tree Interpreter
  The abstract syntax tree (ATS) represents source code in the form of a tree. This tree conveys the structure of the source code to the interpreter. ATS interpreter interprets the abstract syntax tree to generate a machine code.
• Self-Interpreter
  This interpreter can interpret themselves. The most popular self-interpreter is a BASIC interpreter. Self-interpreter is created in case no compiler exists for a particular language.

Conclusion

So, in this way, assemblers and interpreters differ from each other. We have discussed both of these language translators in detail, along with their types and working.