A programming language can be arranged or interpreted. A compiler figures out what a computer will do. The interpreter goes through the source code line by line, figuring out what it is doing as it goes. Interpreting language is flexible, and each data is formed in a specific way. The first step is lexing or turning language into tokens. Tokens are a small unit of language. It might be a variable or function name, an operation or number.
Lexer must produce all the information needed. Lexer removes comments and detects if something is a number or identifier. The second stage is a parser. Parser adds structure to the ordered list of tokens the lexer produces. Interpreted languages are straightforward to design, build and learn. The first high-level programming language was called Plankalkul, which was created between 1942 and 1945.