The mode of operation and contents of a custom-made plug-in memory device for Hewlett-Packard HP41CV calculators (or HP41C with Quad Memory Module) are briefly presented. The module contains 15 of the 30 programs for fish stock assessment documented in the manual by Vakily, J.M., M.L Palomares and D. Pauly. 1986. Computer programs for stock assessments: applications for the HP41 CV calculator. FAO Fish. Tech. Pap. 101, Suppl. 1, Rome, 255 p., namely FB 1-3, 6, 7, 9, 12, 14, 17, 18, 20-22, 25 and 26, covering length-weight relationship: gear selection; growth parameter estimation; total, natural and fishing mortality estimation; yield-per-recruit; and virtual population analyses as well as various length-structured and surplus-production models. The manual must be consulted when using this module.