Konrad Zuse in the context of Atanasoff–Berry computer

Colossus was a set of computers developed by British codebreakers in the years 1943–1945 to help in the cryptanalysis of the Lorenz cipher. Colossus used thermionic valves (vacuum tubes) to perform Boolean and counting operations. Colossus is regarded as the world's first programmable, electronic, digital computer (the first electromechanical being Konrad Zuse's Z3 completed in Berlin in 1941), although it was programmed by switches and plugs and not by a stored program.

Colossus was designed by General Post Office (GPO) research telephone engineer Tommy Flowers based on plans developed by mathematician Max Newman at the Government Code and Cypher School at Bletchley Park.

A carry-lookahead adder (CLA) or fast adder is a type of electronics adder used in digital logic. A carry-lookahead adder improves speed by reducing the amount of time required to determine carry bits. It can be contrasted with the simpler, but usually slower, ripple-carry adder (RCA), for which the carry bit is calculated alongside the sum bit, and each stage must wait until the previous carry bit has been calculated to begin calculating its own sum bit and carry bit. The carry-lookahead adder calculates one or more carry bits before the sum, which reduces the wait time to calculate the result of the larger-value bits of the adder.

Already in the mid-1800s, Charles Babbage recognized the performance penalty imposed by the ripple-carry used in his difference engine, and subsequently designed mechanisms for anticipating carriage for his never-built analytical engine. Konrad Zuse is thought to have implemented the first carry-lookahead adder in his 1930s binary mechanical computer, the Zuse Z1. Gerald B. Rosenberger of IBM filed for a patent on a modern binary carry-lookahead adder in 1957.