"The Nintendo DS is backwards compatible with Game Boy Advance (GBA) cartridges. The smaller Nintendo DS game cards fit into Slot 1 on the top of the system, while Game Boy Advance games fit into Slot 2 on the bottom of the system. The Nintendo DS is not compatible with games for the Game Boy Color and the original Game Boy, due to a slightly different form factor, voltage requirements, and the absence of the compatibility mode. The Sharp Z80 compatible processor used in the older systems is still included, and indeed necessary for some GBA games that use the older sound hardware.
On the top of the device are two shoulder buttons, a game card slot, a stylus holder and a power cable input. The bottom features the Gameboy Advance game cart slot."