[solved] [C++] 0a100? What is this?

Question

I was experimenting in C++ Sololearn Playground.
I wanted to test if there is a specified syntax for numbers written in other number system (like in Python).
And found this:
https://code.sololearn.com/cFK6qJykmsjJ/?ref=app
Could you, please, give links for information on this topic?
(I thought that this question is not open-ended, but feel free to inform if it is open-ended)

Answer 1

get
the `operator "" identifier` can be defined for literals to provide functionality for the syntax
`<literal><identifier>`
For example,
https://code.sololearn.com/cJ5yqJmsz2Gn/?ref=app

And that is why, the error message in your code says that `operator""a100` is not defined. Details about it here
https://en.cppreference.com/w/cpp/language/user_literal

Answer 2

get , what you presented looks like a representation / literal for numbers (integers). but this literal containing an "a" is not valid. you can use like:

0b101 for binary numbers (base 2)
0o101 for octal numbers (base 8)
0x101 for hex numbers (base 16)

i am not sure if you can define your own literals.

you may find some more information here:
https://en.cppreference.com/w/cpp/language/integer_literal