This booklet is an operating guide and collection of worked exercises for an electronic, non-printing desktop calculator. It introduces the machine’s features and demonstrates its use in commercial, mathematical and statistical calculations The introduction describes a calculator built with integrated circuits, weighing approximately 6.5 kg. Its features include a sixteen-digit capacity for addition and subtraction, automatic decimal positioning, two accumulating memory registers and automatic square-root extraction. The stated operating speeds are 30 milliseconds for addition and subtraction and 300 milliseconds for multiplication and division. It explains the keyboard and controls, including clearing an entire calculation or only the latest entry, selecting decimal precision and rounding, handling negative results, exchanging the two calculating registers and recalling stored values. A constant key allows repeated multiplication or division by the same number. An error indicator warns of exceeded capacity, excessive decimal places or division by zero. Most of the document consists of worked examples with illustrated keystroke sequences. These cover: - Basic arithmetic with whole numbers, decimals and negative values, - Chained multiplication and division, powers and square roots, - Accumulating products and quotients in memory, - Using both memories to retain separate totals, - Percentage allocation, discounts, mark-ups and percentage changes, - Preparing an invoice with discounts, packaging charges and sales tax, - More advanced calculations involving compound expressions, Pythagoras’ theorem, standard deviation and the law of cosines. Each exercise specifies the decimal setting and shows the expected result. The emphasis is on teaching operators how to organize calculations and use the memory functions efficiently, progressing from routine office arithmetic to more demanding technical applications.