bits operation symbols 5-bit fast storage (core) address 13-bit (drum) memory address The 18-bit instruction field did not contain a single opcode, but each bit controlled one functional unit of the CPU. Instructions were constructed from these. For example, the bit 'A' meaning to add the content of a memory location to the accumulator could be combined with `N` Nullstellen (zeroing) to turn the Add instruction into a Load. Many combinations are quite unusual by modern standards, like 'LLRA 4' means "multiply the accumulator by three". There also was an assembly-like programming language called "Freiburger Code". It was designed to make writing programs for solving mathematical problems easier than writing machine code, and reportedly did so. See also List of vacuum-tube computers References External links Z22 computer emulator Homepage of the Z22/13 of the university of Karlsruhe (in German), Google translation 1950s computers Vacuum tube computers Computer-related introductions in 1955 Konrad Zuse Computers designed in Germany Serial computers