single register was 32 microseconds, a double register 64 microseconds, and a quadruple register 128 microseconds. That for a delay line was 1024 microseconds. Instruction times were: addition, subtraction, logical operations: 64 microseconds for 32-bit words; double-precision 96 microseconds; multiplication and division 2 milliseconds. For array arithmetic and transfer operations, time per word was 33 microseconds per word for 32 words. Floating-point operations were provided by software; times: 6 milliseconds for addition and subtraction, 5.5 milliseconds average for multiplication, and 4.5 milliseconds average for division. In the early machines, all instructions involving the magnetic drum were interlocked while an operation was in progress. Thus, if the read heads were moved, any subsequent magnetics operation such as to read a track or write a track, were prohibited from proceeding until the first had completed. From about 1957, a new unit, called "rationalised magnetics" was made available. This unit eliminated unnecessary interlocks. Thus, it was possible to execute an instruction that moved the read heads: if followed by an instruction to move the write heads, or to write a track, such instructions were not interlocked, and could proceed in parallel with moving the read heads. The front panel of the DEUCE featured two CRT displays: one showed the current contents of registers, while the other showed the content of any one of the mercury delay line stores. From about 1958, seven extra delay lines could be attached, giving 224 more words of high-speed store. An IBM 528 combined reader–punch could be substituted for the Hollerith equipment, giving the same input/output speeds, in which case the machine was called Mark II. Automatic conversion of alphanumeric data to BCD was provided on input, and the reverse operation on output, for all eighty card columns. On this equipment, reading and punching could proceed simultaneously, if required, and thus could be used for reading in a record, updating it, and then punching an updated record simultaneously with reading in the next record. With the seven extra delay lines, the DEUCE was denoted Mark IIA. Software The principal high-level programming languages were GEORGE (General Order Generator), ALPHACODE, STEVE, TIP, GIP, and ALGOL. Assembler language translators included ZP43 and STAC. Invented by Charles Leonard Hamblin in 1957, GEORGE was closest to present-day programming languages. It used Reverse Polish Notation. For example, to evaluate e = ay2 + by + c, one wrote a y dup × × b