"Calculator"
"Not a number"
"Error"
"."
"0"
"1"
"2"
"3"
"4"
"5"
"6"
"7"
"8"
"9"
"cos"
"ln"
"log"
"sin"
"tan"
"clr"
"del"
"Euler\'s number"
"pi"
"point"
"left parenthesis"
"right parenthesis"
"cosine"
"natural logarithm"
"logarithm"
"sine"
"tangent"
"plus"
"divide"
"factorial"
"times"
"power"
"square root"
"minus"
"clear"
"delete"
"equals"