The MC34063A Series is a monolithic control circuit containing theprimary functions required for DC−to−DC converters. These devicesconsist of an internal temperature compensated reference, comparator,controlled duty cycle oscillator with an active current limit circuit,driver and high current output switch. This series was specificallydesigned to be incorporated in Step−Down and Step−Up andVoltage−Inverting applications with a minimum number of externalcomponents.
I think it's in the wrong category. It better be in the "Regulator" section, otherwise it might be unnoticed to many people visiting this site !
Here is an online calculator for external components selection for this converter :
http://www.nomad.ee/micros/mc34063a/index.shtml
for Boosting 12 volt from 3-5 Volt !!