The classic B747 'Jumbo' shape is cleverly designed to allow the aircraft to fulfill a number of roles. The pilots were positioned way up high to allow 'front loading' of the cargo carrying variant of the series (as LoadToad suggests there was originally a military heavy lift role envisaged for the B747) Putting the flightdeck up high allowed the addition of a fairly simple hinged nose arrangement (hinged at the top) as all the control cables, wiring looms etc ran from the flightdeck along the spine of the aircraft and therefore allowed for a very cavernous cargo area which could be accessed very easily through the huge hinged nose you'll find that the diameter of the door space was such that it allowed maximum use of the cargo space behind it. In the passenger carrying variants (Built without a hinging nose!)the airlines often used the forward cabin for their first class product, the upper deck being very small in the early 747's often wasn't used for passengers. In later variants Boeing recognised the appeal of flying 'up top' so the first (stretched) 'big tops' appeared and were an instant success for airlines.
Believe it or not despite it's shape the good old B747 can actually cruise a wee bit faster than some other modern aircraft on the market these days, the B747/400 will happily sit at .85Mach (nearly 570mph) not bad for a big bird with a blunt nose!
enjoy your pint
