Since PostgreSQL is open source software, source code is publicly available and it can be installed by building (compiling and linking) from source code. To build by yourself, you need tools and environment for development including C compiler, but pre-built packages are also distributed, so no compiler is necessary when installing using package.

For prebuilt packages, there are detailed information on the following PostgreSQL development community web page.

http://www.postgresql.org/download/

There are various packages depending on the platform, but many of these are created by organizations different from the development community. In addition, there are multiple types of packages on the same platform, each installation method is very different. Some packages only install programs (executable files and libraries), others automatically create database files and start up database servers automatically.

For many packages, it is necessary to install programs in directories that require OS administrator privileges such as / usr / bin and / usr / lib, or to rewrite system files to set up database for startup, you will need OS administrator privileges (root on Linux) during installation. However, the PostgreSQL server process itself operates under the privileges of OS general users (in most cases postgres users), and PostgreSQL's server administrator user is different from the OS administrator user.

PostgreSQL can install multiple versions on one machine, apart from the installation destination directory, the database file creation location (PGDATA). And the port number, as long as resources such as memory allow it, it can be operated at the same time.

PostgreSQL can install multiple versions on one machine by setting the installation directory, database file creation location (PGDATA), and port number separately. As long as resources such as memory allow it, you can run multiple versions of them simultaneously.

Therefore, the correct answers are C and E.