Abacus

A manual calculating tool consisting of a frame with rods and movable beads used for arithmetic operations. For visually impaired users, adapted versions like the Cranmer abacus feature beads that stay in place when moved and a backing to prevent displacement. The abacus enables blind students to perform addition, subtraction, multiplication, and division through tactile manipulation. While effective for basic calculations, studies show mixed results compared to mental calculation and Braille-based methods, and some educational settings discourage its use for calculations beyond three digits due to complexity.