In circuit diagrams, the arrows shown on symbols for components such as diodes and transistors point in the direction of conventional current flow.
In the 19th century, with the early applications of electricity such as starter motors and light bulbs, there was not an exact understanding of the nature of current flow. It was assumed at the time that electricity flowed from the positive terminal to the negative.
As an extension to MSRA I would say that one can as well use electron current, provided, he follows the same convention throughout the circuit analysis.
All network related laws, minimisation tecniques.....every thing must be "looked" in the same light.