What converts Assembly language to machine code

Question

I am new to programming and I started with C++ language, as far as I know C++ language is converted to assembly language by the C++ compiler (Ex:Visual Studio), but I tried looking up for what converts the assembly language into machine code to be understood and executed by the computer but I couldn't find an answer.

So the question is, where and how is assembly language converted to machine code? is it by some sort of compiler integrated in the OS?

Thanks in advance.

Answer 1

Some compilers (like GNU) convert the C/C++ code into assembly code. A tool called "assembler" converts the assembly code into machine code and a tool called "linker" connects multiple machine-code files into one single executable (.EXE under Windows) file. Most of these compilers allow you to write the resulting assembler code into a file so you can look at the assembler code or modify it.

The assembler and the linker are part of the tool chain which means that they are typically delivered together with the compiler.

Some compilers (like Microsoft) however directly convert C/C++ code into machine language so no assembler is needed any more. Many of these compilers are not able to create assembler code so you cannot write the assembler code into a file.

By the way: There are even compilers (not for C/C++, but for other programming languages) that directly create an .EXE file so no linker is required.

Answer 2

When compiler converts high level code into assembly language which looks something like below -

• MOV AX, [A] ; # Move A to Register Ax
• ADD AX, [B] ; # Add B to A
• IMUL AX ; # Square(A+B)
• MOV [C], AX ;

An assembler converts these assembly instructions to machine code.

Assembly instruction has typical form like : opcode operand [operand]

And if you check microprocessor manual you will get to know how each instruction can be converted to a binary form like 1001000. Some bits are for opcode and some are for operands.

http://www.mathemainzel.info/files/x86asmref.html