how difficult is it to write your own programming language and why does everyone still use languages written from the 80s of the previous millenia

If you ask this question it means you're far from ready to even start making on.

>>105849204
saar please learn better english

>>105848926 (OP)
inb4 OP realize his CPU run ASSEMBLER
First appeared 1947; 78 years ago

>>105848926 (OP)
Everyone uses Rust now

it's not hard to produce something basic. you will learn a lot by just writing a Lisp where you need to handle a callstack, variable lifetimes, etc. adding closures is interesting.
to produce an interesting language that does cool stuff beyond having a "good syntax" is a far more difficult task.
if you want to start, completely ignore reading about lexers and whatever other bullshit that exists. just write a function that takes a UTF8 string of code and evaluates it using a virtual machine. eventually, for efficiency, you will want to convert that string to bytecode prior to running it. if your language semantics lend well to a static program, then converting that bytecode to C or LLVM or whatever will allow for transpilation.

pic related is a Lisp I made without variadic arguments (hence no need for parentheses). this test demonstrates weird scoping behavior.

>>105848926 (OP)
>how difficult is it to write your own programming language
Most CS grads have taken a course that usually involves them writing a basic compiler. It's not hard to make a programming language, but it is hard to make one that is useful with a compiler that can actually actually optimize and give useful error information.
>why does everyone still use languages written from the 80s of the previous millenia
Not much better has come along

english originated in 1st millennium and its final form emerged over 300 years ago, why do we bother using it today?

>>105850995
backward compatibility.