The video card

A video card turns memory and commands into display output. Older educational interfaces keep the visible model simple:

Concept	Role
mode	resolution and pixel format
framebuffer	memory backing the visible image
pitch	bytes from one row start to the next
color format	how color channels are packed
present	make the prepared frame visible

The mode describes dimensions and pixel format. The framebuffer stores pixels. The pitch says how many bytes separate the start of one row from the next. These values come from mode information, not guesses in drawing code.

Text mode vs graphics mode

Text mode stores character cells. It is small and efficient for terminals because firmware or hardware interprets bytes as glyphs and attributes. Graphics mode stores pixels and gives applications control over every point on the screen.

Why pitch exists

Rows may include padding for alignment or device constraints:

offset = y * pitch + x * bytes_per_pixel

not:

offset = (y * width + x) * bytes_per_pixel

If this formula is wrong, rectangles tear, sprites drift, and writes near the right edge corrupt the next row.