Curta

A working model of the Curta Type I mechanical calculator. It boots at rest — all rings at zero — with a demo tape loaded but not yet run. Use the on-screen keypad (or the physical keys) to drive it: dial a setting slider with the number keys 0-9, move the selected slider with , and . , turn the crank with Enter or Space to add the setting to the results counter, press L to lift the carriage so the crank subtracts, shift the carriage a decimal place with [ and ] (for multiplying and dividing), C clears the result and turns rings, S clears the setting. Open the debugger to single-step the operation tape (each hand action is one step), set a breakpoint on an operation, or watch a results-counter digit for writes. The default tape computes 7 × 6 = 42 by cranking the setting 7 six times.

A working model of the Curta Type I mechanical calculator. It boots at rest — all rings at zero — with a demo tape loaded but not yet run. Use the on-screen keypad (or the physical keys) to drive it: dial a setting slider with the number keys 0-9, move the selected slider with , and . , turn the crank with Enter or Space to add the setting to the results counter, press L to lift the carriage so the crank subtracts, shift the carriage a decimal place with [ and ] (for multiplying and dividing), C clears the result and turns rings, S clears the setting. Open the debugger to single-step the operation tape (each hand action is one step), set a breakpoint on an operation, or watch a results-counter digit for writes. The default tape computes 7 × 6 = 42 by cranking the setting 7 six times.

A working model of the Curta Type I mechanical calculator. It boots at rest — all rings at zero — with a demo tape loaded but not yet run. Use the on-screen keypad (or the physical keys) to drive it: dial a setting slider with the number keys 0-9, move the selected slider with , and . , turn the crank with Enter or Space to add the setting to the results counter, press L to lift the carriage so the crank subtracts, shift the carriage a decimal place with [ and ] (for multiplying and dividing), C clears the result and turns rings, S clears the setting. Open the debugger to single-step the operation tape (each hand action is one step), set a breakpoint on an operation, or watch a results-counter digit for writes. The default tape computes 7 × 6 = 42 by cranking the setting 7 six times.