Across the various continents people communicate through language yet language is not limited to the use of a single alphabet. Also images, sounds and signs are part everyday communication among people. Written language is constantly evolving and it differs between continent, country and even among various social groups (f.i. slang).
Saki Mafundikwa, graphic designer and author of Afrikan Alphabets, talked about written forms of communication(past and present) of several African countries during one of the 2013 TED conferences.
If you are interested African linguistics, the Journal of African Languages and Linguistics has several interesting publications.
featured image: taneter.org