I learnt that the Indus valley civilization has a well-planned city and they have many varieties of jobs such as priests, craftsmen, farmers, and traders. They also have seals used for trades and a uniform writing system.
I think they have a system like what we have now except for modern electronic
stuff such as computers, handphones, music players and so on.(images from http://sg.images.search.yahoo.com/search/images?ei=UTF-8&p=indus+valley+civilisation&sado=1&fr2=tab-web&fr=yfp-t-101-s)
