- The World Factbook
The World Factbook provides basic intelligence on the history, people, government, economy, energy, geography, environment, communications, transportation, military, terrorism, and transnational issues for 265 world entities.
- Bantu-speaking people settled in the area now called Angola in 6th century A.D.; by the 10th century various Bantu groups had established kingdoms, of which Kongo became the most powerful. From the late-14th to the mid-19th century, a Kingdom of Kongo stretched across central Africa from present-day northern Angola into the current Congo republics.
- Shift register (Wikipedia)
A shift register is a type of digital circuit using a cascade of flip-flops where the output of one flip-flop is connected to the input of the next. They share a single clock signal, which causes the data stored in the system to shift from one location to the next. By connecting the last flip-flop back to the first, the data can cycle within the shifters for extended periods, and in this configuration they were used as computer memory, displacing delay-line memory systems in the late 1960s and early 1970s.