MSSQL server cannot connect to (local). Erreur de connexion de server à Microsoft Sql Server

trying connect to SQL server via management studio:

Server type: Database Engine
Server name: localhost
Authentication: Windows Authentication
Error TITLE: Connect to Server:

Cannot connect to localhost. A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 – Could not open a connection to SQL Server) (Microsoft SQL Server, Error: 2) The system cannot find the file specified