A slide rule is a mechanical analog device used for mathematical calculations, particularly multiplication, division, and functions like logarithms and trigonometry. It consists of a ruler with a sliding central strip, allowing users to align numbers and perform calculations without the need for electricity or batteries. Invented in the 17th century, the slide rule was widely used by engineers, scientists, and students until the advent of electronic calculators in the late 20th century. Despite its decline in popularity, the slide rule remains a symbol of mathematical ingenuity and is still appreciated by enthusiasts and collectors today.