Text modes: IBM intended that CGA be compatible with a home television set.

When using a direct-drive monitor, the four color bits are output directly to the DE-9 connector at the back of the card.

Within the monitor, the four signals are interpreted to drive the red, green and blue color guns.

For cost reasons, this is not done using an RGB-to-YIQ converter as called for by the NTSC standard, but by a series of flip-flops and delay lines.

[18] The relative luminances of the colors produced by the composite color-generating circuit differ between CGA revisions: they are identical for colors 1-6 and 9-14 with early CGAs produced until 1983,[19] and are different for later CGAs due to the addition of additional resistors.

By setting a hardware register, the blink feature can be disabled, restoring access to high-intensity background colors.

However, unlike the text modes, this also affects the colors displayed on an RGBI monitor, altering them to the cyan/red/white palette seen above.

In this mode, the video picture is stored as a simple bitmap, with one bit per pixel setting the color to "foreground" or "background".

A number of official and unofficial features exist that can be exploited to achieve special effects.

Although a roundabout way of achieving a 16-color graphics display, this works quite well and the mode is even mentioned (although not explained) in IBM's official hardware documentation.

[26][27][28] More detail can be achieved in this mode by using other characters, combining ASCII art with the aforesaid technique.

Using the composite output instead of an RGBI monitor produced lower-quality video, due to NTSC's inferior separation between luminance and chrominance.

By carefully placing pixels in appropriate patterns, a programmer can produce specific cross-color artifacts yielding a desired new color; either from purely black-and-white pixels in 640 × 200 mode, or resulting from a combination of direct and artifact colors in 320 × 200 mode, as seen on the following pictures:

Certain ASCII characters such as U and ‼ are then used to produce the necessary patterns, which result in non-dithered images with an effective resolution of 80 × 100 on a composite monitor.

[34] The 320 × 200 variant of this technique (see above) is how the standard BIOS-supported graphics mode looks on a composite color monitor.

The 640 × 200 variant, however, requires modifying a bit (color burst disable) directly in the CGA's hardware registers.

Being completely dependent on the NTSC encoding/decoding process, composite color artifacting is not available on an RGBI monitor, nor is it emulated by EGA, VGA or contemporary graphics adapters.

The low resolution of this composite color artifacting method led to it being used almost exclusively in games.

This integrated circuit was originally designed only for character-based alphanumeric (text) displays and can address a maximum of 128 character rows.

This arrangement results in additional overhead in graphics modes for software that manipulates video memory.

The higher bandwidth used by 80-column text mode results in random short horizontal lines appearing onscreen (known as "snow") if a program writes directly to video memory during screen drawing.

The BIOS avoids the problem by only accessing the memory during horizontal retrace, or by temporarily turning off the output during scrolling.

Hence, IBM documentation lists the 80-column text mode as a "feature" only for RGBI and black-and-white composite monitors.

A command included with PC DOS permitted switching the display output between the CGA and MDA cards.

Some of the software that supported the board was: BYTE in January 1982 described the output from CGA as "very good—slightly better than color graphics on existing microcomputers".

[4] PC Magazine disagreed, reporting in June 1983 that "the IBM monochrome display is absolutely beautiful for text and wonderfully easy on the eyes, but is limited to simple character graphics.

[40] In a retrospective commentary, Next Generation also took a negative view on the CGA, stating, "Even for the time (early 1980s), these graphics were terrible, paling in comparison to other color machines available on the market.

The Color Graphics Adapter uses a standard DE-9 connector for direct-drive video (to an RGBI monitor).

The Color Graphics Adapter uses a standard RCA connector for connection to an NTSC-compatible television or composite video monitor.