A calculadora Madas 20BZS é uma máquina de calcular portátil, uma peça icónica da história dos anos 1950 feita por H. W. Egli na Suíça. Infelizmente, esta Madas 20BZS já não tem o cabo eléctrico original, mas com certeza o antigo teria que ser substituído.
MADAS significa Multiplicação-Divisão-Adição-Subtração Automática.

Com a foto presente acima, identificar:
1. Carriage release catch, Allows the carriage to be removed for maintenance.
2. Register III, Input display register.
3. Auto tabulation switch, set whether carriage returns to chosen tab position after multiplication.
4. Keyboard, keyboard for inputting 10-digit number. Entered number is shown in register III.
5. Transfer I→IV, Transfer number from main register to multiplication register.
6. Set dividend, Clears main register, shifts to chosen tab, adds input without affecting counter.
7. Auto-clear I, Select whether to clear keyboard after addition or subtraction.
8. Clear I, Clear main register.
9. Clear II, Clear counter register.
10. Clear III, Clear keyboard input.
11. Negative Multiplication, Multiply input with multiplication register and subtract from main register.
12. Clear IV, Clear multiplication register.
13. Auto-clear IV, Select whether to clear multiplication register after multiplication.
14. Tabulation, Select the default carriage location for multiplication or division.
15. Split, Split main register so clearing only affects lowest 9 digits.
16. Setting knobs I, Knobs for manually setting a value the main register.
17. Register I, Main register.
18. Register II, Counter register.
19. Counter disable, Disables counter register
20. Stop button, Immediately aborts division, including division by zero.
21. End division, End division after the current digit is calculated.
22. Negative division, Set direction of counter in division.
23. Division, Start division process, dividing main register by input, result in counter.
24. Reverse, Set direction of counter in addition/subtraction.
25. Subtract, Subtract input from main register.
26. Add, Add input from main register.
27. Carriage shift, Shift carriage to the left or right.
28. Column separators, Show a line between keyboard columns, for example for decimal point.
29. Multiplication, Set multiplication register from input (if clear), or multiply input by multiplication register and add to main register.
30. Register IV, Multiplication register
31. Setting knobs IV, Knobs for manually setting a value the multiplication register.