1. work with floating point numbers
2. offer the +, -, ×, ÷ basic binary operators.
3. offer the cos(), sin(), tan(), abs(), x^2, x^3, lg(), rand() basic unary operators.
4. backspace(right side of the display screen) and all clear button
5. a description screen that shows the calculating steps.

1. original ios calculator colors.
2. good screen fit.
3. screen shot below.
   
   

1. work with floating point numbers
2. offer the +, -, ×, ÷ basic binary operators.
3. offer the cos(), sin(), tan(), abs(), x^2, x^3, lg(), rand() basic unary operators.
4. backspace(right side of the display screen) and all clear button
5. click the backspace button "<-" until the last digit left will cause undo.
6. a description screen that shows the calculating steps.
7. add variable using "M" button.
8. using "➝ M" button to set or reset the value of the "M" variable, then recualte the expresstions.

1. original ios calculator colors.
2. good screen fit.
3. screen shot below.
   
   
   
   

1. work with floating point numbers
2. offer the +, -, ×, ÷ basic binary operators.
3. offer the cos(), sin(), tan(), abs(), x^2, x^3, lg(), rand() basic unary operators.
4. backspace(right side of the display screen) and all clear button
5. click the backspace button "<-" until the last digit left will cause undo.
6. a description screen that shows the calculating steps.
7. add variable using "M" button.
8. using "➝ M" button to set or reset the value of the "M" variable, then recualte the expresstions.
9. using "~" button to generate graph for function that user input.

1. original ios calculator colors.
2. good screen fit.
3. screen shot below.