Schematic input does not validate against the Schema: {"version":"7.3.8","name":"first_app","routing":true,"style":"css"} Errors: Data path ".name" should match format "html-selector".

Schematic input does not validate against the Schema: {"version":"7.3.8","name":"first_app","routing":true,"style":"css"} Errors: Data path ".name" should match format "html-selector".

This is the angular error. Angualar doesn't support "app", "my_app", "my/app".
To correct above error you should write first-app instead of first_app , this is becase angular doesn't support underscore in project name. You should type ng new first-app to your terminal.

ng new first-app