SQL plus doesn't show English as shown here
and it also returns error for system user name and password, even the user name and password are correct! The error is ORA-12560:TNS:protocol adapter error, what should I dخ??
This problem occurs when console codepage mismatch Oracle client NLS_LANG parameter.
NLS_LANG parameter you can set changing Windows-registry key HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE\NLS_LANG or defines environment variable NLS_LANG.
Example of setting parameter for console session:
set NLS_LANG=AMERICAN_AMERICA.WE8ISO8859P1
Codepage of console you can set execute this:
chcp 850