The document combines operating instructions with worked examples for business, statistics and engineering. The FRIDEN: 130 is described as a silent, solid-state desktop calculator with a cathode-ray-tube (CRT) display showing four 13-digit registers simultaneously. These registers hold entered numbers and intermediate results. They operate as a stack: arithmetic combines the two lowest registers, while values stored above them move down as calculations proceed. A separate, undisplayed memory stores a number for repeated use. The opening sections explain the keyboard and controls, including Enter, Repeat, Change Sign, Store, Recall, Clear Entry and Clear All. A decimal selector provides settings of 0, 2, 5, 7 or 13 decimal places. The manual also explains overflow protection and the relationship between decimal placement and available numerical capacity. Step-by-step examples demonstrate addition, subtraction, multiplication, division, squaring, powers, chained calculations and the accumulation of products or quotients. Each example presents the mathematical solution alongside the numbers to enter and the exact sequence of keys to press. The applications cover several fields: - Business and finance: invoicing, sales tax, discounts, percentage changes, profit margins, simple and compound interest, instalment loans and mortgage payments, - Statistics and insurance: probability, actuarial calculations, life-insurance probabilities and standard deviation, - Mathematics and engineering: geometric series, sphere volumes, angular and other unit conversions, sector areas, interpolation, polynomial and integral evaluation, simultaneous equations using determinants, and the cosine law. Square and cube roots are calculated through repeated approximations, using ordinary arithmetic and memory operations. The manual supplies the formulas, starting estimates and keyboard sequences. Its final technical sections explain how to handle calculations exceeding the normal capacity and how to obtain a multiplication result of up to 26 digits in two separate parts. The manual illustrates how the calculator’s visible registers and memory supported substantial professional calculations through carefully organised manual keyboard procedures.