From a software point of view, a frame buffer is a 1024 x 512 two-dimensional address space composed of 16-bit pixels. The top left pixel has the coordinates (0, 0) and the bottom right pixel has the coordinates (1023, 511). Each pixel is made up of three 5-bit data items indicating RGB brightness values, each ranging from 0~31, and a semi-transparency flag. The semi-transparency flag is only valid when the pixel is used as a texture.
The part of the frame buffer that is displayed is a rectangular area known as the 'display area'. Based on the GPU display function, the display area can be selected as a pair of values ranging from 256 x 240 to 640 x 480 for NTSC and 256 x 256 to 640 x 512 for PAL. Interlace mode is on when the display height is 480 for NTSC or 512 for PAL.
Drawing is limited to a rectangular area, referred to as the 'drawing area' within the frame buffer. The drawing area may be any size that can be accommodated in the frame buffer.