Not all of the characters have visible symbols. Anything below whatever it is, 0x20 or somesuch, won't, for example.

The Glyph Drawing Club blog has a fantastic post about the "small house" to be found in IBM code page 437. Unicode has inherited it (hopefully it'll show up quoted below in whatever form your system ...

A font that uses the extended ASCII characters as defined by IBM for the original PC. The OEM or DOS/OEM character set contains line draw and other symbols commonly used by earlier DOS programs to ...