1. That version solved problems faster than 100 human operators with mechanical desk calculators . 2. In the 1950s and 1960s, economists used electromechanical desk calculators to calculate regressions. 3. The firing table calculations were accomplished by about one hundred women operating mechanical desk calculators . 4. Another program written by the PDP-1 hackers was Expensive Desk Calculator , in a similar vein. 5. American mathematicians John Wrench and Levi Smith reached 1, 120 digits in 1949 using a desk calculator . 6. Then, with the aid of a mechanical desk calculator obtained result in much better agreement with experiment. 7. This error was highlighted in 1944 by D . F . Ferguson ( using a mechanical desk calculator ). 8. Beside him was a holstered pistol, next to a desk calculator , a box of tissues and two bottles of mineral water. 9. These were calculated using the only available tools of the time, an eight-digit mechanical desk calculator and a very large slide rule. 10. Beside him was a holstered pistol with belt, next to a desk calculator , a box of tissues and two bottles of mineral water.