Symbian’s introductory training covers Active Objects. Active Objects are a Symbian specific method of providing co-operative multitasking. During the introduction to Active Objects we are all told about how inefficient and bloated multi threaded applications can be. Each thread requires heap and stack space, it requires kernel resources to provide for the context switching, and time slicing. All of this is an overhead on a device with limited resources. Instead Symbian provide Active Objects. We can have many Active Objects within a single process all waiting on different events. This means that we do not need as many threads, and hence we consume less resources. More here.