The people of Indus valley used hieroglyphs just like the Egyptians. At first Indus valley people used only pictures. Later, they added writing to the pictures. Indus valley people wrote the first line of writing from left to right, the second from right to left, and so on. The writing doesn't tell us much. It used at least 419 different signs. Most writing was to do with trade, government, or religion.
Signs in Indus writing.
http://www.bbc.co.uk/schools/primaryhistory/indus_valley/art_and_writing/
Signs in Indus writing.
http://www.bbc.co.uk/schools/primaryhistory/indus_valley/art_and_writing/