1GL

A first-generation language (or 1GL) is one single language: the machine language.

2GL

Second-generation languages (2GLs) include assembly language.

In 2GL language, the programmer is obligated to deal with very low levels of detail within the computer's hardware to perform relatively common coding tasks.

For example, in order to write a command to add two numbers together, you write code that identifies which registers will contains the first number and second number. Then you will invoke a command to perform the arithmetic and store the result in a third location.

3GL

high level language or Third-generation languages (3GLs) were create primarily to reuse code via block but they also include common language features such as:

• variables
• constants,
• flow constructs (if then),
• loops,
• error handling,
• and more.

The code is translated to machine code for the computer to actually execute.

4GL

SQL is the only widely used 4GL in commercial use today.

Artificial intelligence languages are also classified as 4GL.

Declarative language and dsl could be classified as 4GL.