I tried almost all the articles there is on this error. But in my case the services aren't installed. So i can't change them. I had 10g installed before but i needed to use Oracle for python too so I removed that. And also i did reset my pc(keep my files) after that. But now i have tried multiple times to install Oracle 18c but not working. I.e modifying listener and sqlplus sys/mypassword as sysdba or many more.
These are the screenshots.
This is very frustrating. Any suggestions? Also What is the alternative for homepage of 10g in 18c.
I also tried running setup.exe from zip folder directly. But no luck.
Your screen shots clearly show that the services are indeed installed, your assertion otherwise notwithstanding. You even have sqlplus waiting to do your bidding. But you invoke it incorrectly.
The protocol error (ora-12560) occurs when 1) you do not specify a connect string when you invoke sqlplus thus causing it to try to connect to a local database specified by the environment variable ORACLE_SID, and 2) the environment ORACLE_SID does not specify an actual local database.
Unfortunately, your screen shot does not show how you invoked sqlplus, thus losing important diagnostic info. Far better to start cmd.exe, invoke sqlplus, then copy the entire text and paste that into your question, with formatting. I leave it as an exercise for the student to research how to do those elementary tasks.