What is the difference between high level middle level low level languages?

Answer 1

The more that the language does for you, the higher level it is considered.

The ultimate low level language is machine language. With machine language you have to tell the computer literally everything to do at a very detailed level. You are essentially speaking in 1s and 0s -- the language of the processor. This means managing the memory used, deciding where and how you will store and retrieve information... with machine language, there is no notion of how to generate a user interface ... you would be face with the prospect of redesigning how to display windows and buttons, how to make them "act", how to manage a user interaction. Of course nobody but chip designers would use that low level a language anymore ...

With a higher level language, the language does more for you. It "knows" how to store and retrieve complex data structures -- it knows how to read and write from files, it knows how to draw windows and buttons -- so you can use a couple of commands to display a window, where it would take literally hundreds of lines of code to do the same thing in a low level language.

Answer 2

The level is simply an indication of the level of abstraction between the programming language and the machine itself. The greater the level of abstraction, the lower the level of interaction with the hardware and vice versa.

Machine code has no abstraction whatsoever and therefore the highest level of interaction. Hand-crafting machine code is affectionately known as "banging the metal". Machine code is procedural in nature resulting in "spaghetti code" that is difficult to both read and maintain. Machine code is non-portable.

Assembly is an example of a low-level language. Assembly is a symbolic language that maps 1:1 with the machine code produced by the assembler. This gives the programmer a high degree of control over the machine code and, while easier to program than machine code, the language is still procedural, spaghetti in nature and non-portable.

C is also regarded as a low-level language, but is much easier to work with than assembly and is highly portable (the same source can be compiled upon different machines). Programs can be modularised and structured through procedure calls, but the programmer still has a great deal of control over the resultant machine code because all instructions can be mapped 1:1 with assembly and conditional compilation can be used to cater for machine-specifics.

Java is a high-level language with no direct interaction with the hardware. Code is written to suit a virtual machine, the Java Virtual Machine (or JVM), rather than a physical machine. The JVM is a runtime program that interprets the compiled byte source to produce the required machine code. Each physical machine has its own implementation of the JVM thus programs can be compiled on any platform and the same compilation can then be executed on any machine with the suitable JVM implementation.

A mid-level programming language is one that allows both high and low level programming. C++ is a typical example since it evolved predominantly from low-level C but incorporates high-level Simula-like object-oriented programming (OOP). The language has evolved to include generic programming techniques through function and class templates which, combined with OOP, allow programmers to express ideas directly in code. This makes it possible to write highly-complex, highly-scalable, robust programs much more easily and often with greater efficiency than would be possible with C alone.