Multi-mode computing systems for point of sale transactions are disclosed. According to an aspect, a computing system includes a first housing and a processing device disposed in the first housing. A user interface and a first input/output interface is integrated with the first housing and in communication with the processing device. The first input/output interface is configured to receive power for delivery to the processing device. A second housing is configured to carry the first housing. An attachment mechanism is configured to selectively attach together the first housing and the second housing for carry of the first housing. A second input/output interface is configured to be communicatively coupled to the first input/output interface when the first housing and the second housing are attached. A power source is connected to the second input/output interface for delivery of power to the processing device via the first input/output interface.