Box-drawing characters

[2][3] On many Unix systems and early dial-up bulletin board systems the only common standard for box-drawing characters was the VT100 alternate character set (see also: DEC Special Graphics).

The escape sequence Esc ( 0 switched the codes for lower-case ASCII letters to draw this set, and the sequence Esc ( B switched back: On some terminals, these characters are not available at all, and the complexity of the escape sequences discouraged their use, so often only ASCII characters that approximate box-drawing characters are used, such as - (hyphen-minus), | (vertical bar), _ (underscore), = (equal sign) and + (plus sign) in a kind of ASCII art fashion.

Modern Unix terminal emulators use Unicode and thus have access to the line-drawing characters listed above.

A character cell is divided in 2×3 regions, and 26 = 64 code positions are allocated for all possible combinations of pixels.

The Sinclair ZX80, ZX81, and ZX Spectrum included a set of text semigraphics with quadrant-based block elements.

[6] The BBC Master and later Acorn computers have the soft font by default defined with line drawing characters.

Sample diagrams made out of the standard box-drawing characters, using a monospaced font:

Midnight Commander using box-drawing characters in a terminal emulator
PET 2001 keyboard layout, illustrating PETSCII graphics characters
ZX81 semigraphics