STO+

This operation takes a symbol and another item of just about any numeric type (real, complex, integer or matrix). The symbol can be in either position on the stack and the other item on the stack must be a numeric input. It gets the value of that symbol from the current directory and adds that value with the other numeric item from the stack. It then stores the result back to the symbol. The old value of the symbol is replaced with the new calculated value. Nothing is returned on the stack because the result is stored in the symbol.