Large display Large, easy-to-read display. Two-way power (Solar + Battery) Solar powered when light is sufficient, battery powered when light is insufficient. Key rollover Key operations are stored in a buffer, so nothing is lost even during high-speed input. Plastic keys Designed and engineered for easy operation. Tax calculation Automatic calculation of price plus tax, price less tax, discount, selling price, tax amount, discount amount, and margin amount. Profit margin percent " % " key gives quick access to prices and profits, and also delivers add-ons, discounts, ratios and increase/decrease values. Function command signs A symbol (+, -, ×, ÷) on the display indicates the status of operation you are currently performing.