Differentiate between assemblers and compilers

Answer 1

Assembly programming is low-level programming and is machine-dependant. Assembly language makes it easier for programmers to write machine-specific code. While this gives the programmer a high-degree of control over the resultant machine code, programs have to be written in minute detail at the machine level. Assemblers perform a 1:1 translation from the source code and are therefore extremely simple programs. However, assembly language is non-portable. Each machine architecture has its own specific machine code so the assembly code specific to one machine architecture cannot be assembled upon a different architecture.

Compiled-language programming is high-level programming. By high-level we mean there is high degree of abstraction between the code you write and the machine code produced by the compiler. Compiled-languages are generally portable. That is, the same source code can be compiled on any machine that has a suitable compiler, where the compiler itself is machine-dependant, but the source code is not.

While assembly programming requires programs be written in minute detail at the machine level, compiled-language programming is more abstract. A single high-level statement can easily produce hundreds of individual machine-code instructions. While the high-level programmer has much less control over the resultant machine code, compilers also incorporate code optimisers that can analyse the source code to produce the most efficient machine code -- often surpassing anything that an assembly programmer can produce by hand. Ultimately, compilers allow programmers to produce more machine code much more quickly and with more accuracy (fewer errors), and typically with greater efficiency.

Even so, there are still some things that can only be achieved with assembly. For instance, a compiler's optimisers might "over think" a problem and produce less-than-optimal machine code for a specific routine. In these cases, the high-level programmer can simply insert inline assembly instructions where required. Alternatively, the compiler can be used to emit assembly instructions rather than machine code, and that assembly code can then be tweaked where required.