Raspberry Pi 1 Model A
Model A is the lower-spec variant of the Raspberry Pi, with 256 MB of RAM, one USB port and no Ethernet port.
This model is usually bought for embedded projects: because it’s missing a few ports and an Ethernet chip, the Model A is lighter and consumes less power than a Model B. We see a lot of Model As used in robotics; and also in projects where weight and low power are paramount, such as the very popular high-altitude ballooning high-jinks pioneered by Dave Akerman, and now being reproduced in schools around the world. Model A in combination with a wifi dongle is also ideal for users who just want a Raspberry Pi to act as a media centre running behind their television.