How can I change the character encoding to 7-bit?

edit

I'm assuming you mean the UTF-8 banner that appears when launching the SageMath REPL (read-eval-print loop) in the command-line:

$ sage
┌────────────────────────────────────────────────────────────────────┐
│ SageMath version 7.2, Release Date: 2016-05-15                     │
│ Type "notebook()" for the browser-based notebook interface.        │
│ Type "help()" for help.                                            │
└────────────────────────────────────────────────────────────────────┘
sage:

An alternative is to launch Sage in "quiet" mode, without the banner:

$ sage -q
sage:

If you want the version number, use any of these:

$ sage -version
SageMath version 7.2, Release Date: 2016-05-15

$ sage -v
SageMath version 7.2, Release Date: 2016-05-15

$ sage -dumpversion
7.2

Note (how could one find that out by oneself?):

• sage -h or sage -help will give you the most common flags you can use.
• sage -advanced will give you a complete list, which includes -q.