Screen buffer

A framebuffer (frame buffer, or sometimes framestore) is a portion of RAM containing a bitmap that is used to refresh a video display from a memory buffer containing a complete frame of data. Modern video cards contain framebuffer circuitry at their core. This circuitry converts an in-memory bitmap into a video signal that can be displayed on a computer monitor.

In computing, a screen buffer is a part of computer memory used by a computer application for the representation of the content to be shown on the computer display. The screen buffer may also be called the video buffer, the regeneration buffer, or regen buffer for short. Screen buffers should be distinguished from video memory. To this end, the term off-screen buffer is also used.

The information in the buffer typically consists of color values for every pixel to be shown on the display. Color values are commonly stored in 1-bit binary (monochrome), 4-bit palettized, 8-bit palettized, 16-bit high color and 24-bit true color formats. An additional alpha channel is sometimes used to retain information about pixel transparency. The total amount of memory required for the framebuffer depends on the resolution of the output signal, and on the color depth or palette size.

Computer researchers had long discussed the theoretical advantages of a framebuffer, but were unable to produce a machine with sufficient memory at an economically practicable cost. In 1969, A. Michael Noll of Bell Labs implemented a scanned display with a frame buffer. Later on, the Bell Labs system was expanded to display an image with a color depth of three bits on a standard color TV monitor. An even earlier scanned display was implemented at the Brookhaven National Laboratory. Advances in integrated-circuit memory in the 1970s made it more cost practical to create framebuffers capable of holding a standard video image.

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