A colorful calculator with BIG buttons, LOTS of features, and fully customizable.

・Dual-line display - shows the input and result at the same time
・History tape - saves every calculation, time and date stamped
・Memory buttons - shows its value on the display
・Percentage and backspace button
・Scientific functions
・6 layouts (3 portrait, 3 landscape)
・10 color themes
・Multi-line input for really long equations
・Automatic scientific formatting
・Label any calculation in the history tape
・E-mail a calculation or the entire history tape
・VoiceOver accessibility
・iOS 9 Split View
・3D Touch
・Today Widget (In App Purchase)
・Multiple History Tapes (In App Purchase)

Gestures

・Swipe down to see the history tape
・Tap & hold on the result to copy
・Tap & hold on the input to move the cursor, copy, paste

Customize

・Font Size
・Bold Font
・Color Theme
・Light Tape Background
・Show Layout Button
・Allowable Layouts
・Show Memory Buttons
・Backspace Button (Solid, Arrow)
・Replace ÷ Button With /
・Replace E Button With Hidden, EE, 00, or 000
・Show Thousands Separators
・Minimum Decimal Digits
・Maximum Decimal Digits
・Sound
・Equals Repeat
・Left-Handed Mode

URL Scheme: calculatorhdpro://