BT
  /F13 12 Tf
  288 720 Td
  (ABC) Tj
ET

that is:

begin a text object.
set the font and font size to use.
specify a starting position for the text.
paint the glyphs for a string of characters at that position.
end of text object.

(default glyph size: 1/72 inch, or UserUnit of the Page dict)
(text space: text matrix, transformation matrix, unit, ...)

0.5 g
  fill 50% gray.

1 Tr
  set mode to stroke.
2 w
  (stroke) line width 2 units
7 Tr
  set mode to clipping.

(see page 253)

text show operators:
	<string> Tj    show string
	<string> '     move to next line, show string
	<word-spacing> <character-spacing> <string> "     move to next line, show string
	<word-spacing> Tw       set word spacing
	<character-spacing> Tc  set character spacing
	<array> TJ     show string, array contains numbers and strings. numbers denote -1/1000 of cursor movement before showing the next item. (positive: left or down, in the default coordinate system).

other:
	general graphics state:
		w J j M d ri i gs (Table 57)
	special graphics state:
		q Q cm (Table 57) (OK)
	Path construction:
		m l c v y h re (OK)