module vt100
	character, parameter :: EFFECT_NORMAL    = "0"
	character, parameter :: EFFECT_BOLD      = "1"
	character, parameter :: EFFECT_ITALIC    = "3"
	character, parameter :: EFFECT_UNDERLINE = "4"
	character, parameter :: EFFECT_BLINK     = "5"
	character, parameter :: EFFECT_REVERSE   = "7"
	character, parameter :: COLOUR_GREY      = "0"
	character, parameter :: COLOUR_RED       = "1"
	character, parameter :: COLOUR_GREEN     = "2"
	character, parameter :: COLOUR_YELLOW    = "3"
	character, parameter :: COLOUR_BLUE      = "4"
	character, parameter :: COLOUR_PINK      = "5"
	character, parameter :: COLOUR_CYAN      = "6"
	character, parameter :: COLOUR_WHITE     = "7"
end module vt100

program xscii
	use vt100

	integer :: code = 0

	do while (code /= 2 ** 7)
		call print_base (code,  2, 7, '0', COLOUR_WHITE, EFFECT_NORMAL)
		call print_base (code,  8, 3, '0', COLOUR_CYAN,  EFFECT_NORMAL)
		call print_base (code, 10, 3, ' ', COLOUR_CYAN,  EFFECT_ITALIC)
		call print_base (code, 16, 2, '0', COLOUR_CYAN,  EFFECT_BOLD)
		call print_code (code,             COLOUR_BLUE,  EFFECT_BOLD)
		call print_name (code,             COLOUR_PINK,  EFFECT_NORMAL)
		if (modulo (code, 2) /= 0) then
			call print_line
		end if
		code = code + 1
	end do
end program xscii

subroutine print_line
	print *
end subroutine print_line

subroutine print_letter (letter)
	character, intent (in) :: letter

	write (*, '(a)', advance='no') letter
end subroutine print_letter

subroutine print_string (string)
	character (len=*), intent (in) :: string

	write (*, '(a)', advance='no') string
end subroutine print_string

subroutine print_align (limit, align)
	integer,   intent (in) :: limit
	character, intent (in) :: align

	do i = 1, limit
		call print_string (align)
	end do
end subroutine print_align

subroutine print_colour (colour, effect)
	use vt100

	character, intent (in) :: colour
	character, intent (in) :: effect

	call print_string (char (27) // "[" // effect // ";3" // colour // "m")
end subroutine print_colour

subroutine print_cancel
	call print_string (char (27) // "[0m")
end subroutine print_cancel

subroutine print_bar
	use vt100

	call print_colour (COLOUR_GREY, EFFECT_BOLD)
	write (*, '(a)', advance='no') " | "
	call print_cancel
end subroutine print_bar

subroutine print_base (code, base, limit, align, colour, effect)
	use vt100

	integer,   intent (in) :: code
	integer,   intent (in) :: base
	integer,   intent (in) :: limit
	character, intent (in) :: align
	character, intent (in) :: colour
	character, intent (in) :: effect

	character (16) :: cypher
	character (16) :: output
	integer        :: length
	integer        :: modify

	cypher = "0123456789ABCDEF"
	output = "                "
	length = 1
	modify = code
	call print_bar
	call print_colour (colour, effect)
	if (modify == 0) then
		call print_align (limit - 1, align)
		call print_string ("0")
		call print_cancel
		return
	end if
	do while (modify /= 0)
		i = modulo (modify, base) + 1
		output (length : length) = cypher (i : i)
		length = length + 1
		modify = modify / base
	end do
	call print_align (limit - length + 1, align)
	do while (length /= 1)
		call print_letter (output (length - 1 : length - 1))
		length = length - 1
	end do
	call print_cancel
end subroutine print_base;

subroutine print_code (code, colour, effect)
	use vt100

	integer,   intent (in) :: code
	character, intent (in) :: colour
	character, intent (in) :: effect

	character (3), dimension (32) :: code_name

	code_name = [                                                                                                           &
		"NUL", "SOH", "STX", "ETX", "EOT", "ENQ", "ACK", "BEL", "BS ", "HT ", "LF ", "VT ", "FF ", "CR ", "SO ", "SI ", &
		"DLE", "DC1", "DC2", "DC3", "DC4", "NAK", "SYN", "ETB", "CAN", "EM ", "SUB", "ESC", "FS ", "GS ", "RS ", "US "  &
	]

	call print_bar
	call print_colour (colour, effect)
	if (code == 2 ** 7 - 1) then
		call print_string ("DEL")
		call print_cancel
		return
	end if
	if (code <= 2 ** 5 - 1) then
		call print_string (code_name (code + 1))
	else
		call print_letter (char (code))
		call print_string ("  ")
	end if
	call print_cancel
end subroutine print_code

subroutine print_name (code, colour, effect)
	use vt100

	integer,   intent (in) :: code
	character, intent (in) :: colour
	character, intent (in) :: effect

	character (24), dimension (128) :: code_name

	code_name = [                                                                                                           &
		"Null                    ", "Start of heading        ", "Start of text           ", "End of text             ", &
		"End of transmission     ", "Enquiry                 ", "Acknowledge             ", "Bell                    ", &
		"Backspace               ", "Horizontal tab          ", "Line feed               ", "Vertical tab            ", &
		"Form feed               ", "Carriage return         ", "Shift out               ", "Shift in                ", &
		"Data link escape        ", "Device control 1        ", "Device control 2        ", "Device control 3        ", &
		"Device control 4        ", "Negative acknowledge    ", "Synchronous idle        ", "End transmission block  ", &
		"Cancel                  ", "End of medium           ", "Substitute              ", "Escape                  ", &
		"File separator          ", "Group separator         ", "Record separator        ", "Unit separator          ", &
		"Space                   ", "Exclamation mark        ", "Speech mark             ", "Number sign             ", &
		"Dollar sign             ", "Percent                 ", "Ampersand               ", "Quote                   ", &
		"Open parenthesis        ", "Close parenthesis       ", "Asterisk                ", "Plus                    ", &
		"Comma                   ", "Minus                   ", "Period                  ", "Slash                   ", &
		"Zero                    ", "One                     ", "Two                     ", "Three                   ", &
		"Four                    ", "Five                    ", "Six                     ", "Seven                   ", &
		"Eight                   ", "Nine                    ", "Colon                   ", "Semicolon               ", &
		"Open angled bracket     ", "Equal                   ", "Close angled bracket    ", "Question mark           ", &
		"At sign                 ", "Uppercase A             ", "Uppercase B             ", "Uppercase C             ", &
		"Uppercase D             ", "Uppercase E             ", "Uppercase F             ", "Uppercase G             ", &
		"Uppercase H             ", "Uppercase I             ", "Uppercase J             ", "Uppercase K             ", &
		"Uppercase L             ", "Uppercase M             ", "Uppercase N             ", "Uppercase O             ", &
		"Uppercase P             ", "Uppercase Q             ", "Uppercase R             ", "Uppercase S             ", &
		"Uppercase T             ", "Uppercase U             ", "Uppercase V             ", "Uppercase W             ", &
		"Uppercase X             ", "Uppercase Y             ", "Uppercase Z             ", "Opening bracket         ", &
		"Backslash               ", "Closing bracket         ", "Caret                   ", "Underscore              ", &
		"Grave                   ", "Lowercase a             ", "Lowercase b             ", "Lowercase c             ", &
		"Lowercase d             ", "Lowercase e             ", "Lowercase f             ", "Lowercase g             ", &
		"Lowercase h             ", "Lowercase i             ", "Lowercase j             ", "Lowercase k             ", &
		"Lowercase l             ", "Lowercase m             ", "Lowercase n             ", "Lowercase o             ", &
		"Lowercase p             ", "Lowercase q             ", "Lowercase r             ", "Lowercase s             ", &
		"Lowercase t             ", "Lowercase u             ", "Lowercase v             ", "Lowercase w             ", &
		"Lowercase x             ", "Lowercase y             ", "Lowercase z             ", "Opening brace           ", &
		"Vertical bar            ", "Closing brace           ", "Tilde                   ", "Delete                  "  &
	]

	call print_bar
	call print_colour (colour, effect)
	call print_string (code_name (code + 1))
	call print_cancel
end subroutine print_name