A LIA file is a library file saved in the P-CAD ASCII format. It contains a library of CAD schematic design patterns and symbols in plain text format. LIA files are the ASCII version of LIB P-CAD Binary library files.

The P-CAD ASCII format was developed by P-CAD, short for Personal CAD Systems, a program popular in the 1980s. It was later acquired by several different companies until Altium acquired it in 2000. P-CAD was then retired in 2006. P-CAD had a large segment of Electronic Design Automation (EDA) users with programs specializing in logic simulation, schematic capture, and printed circuit board (PCB) layout design. The P-CAD ASCII format is used to contain the same libraries as the P-CAD Binary format but is saved in text format instead of binary format. You can use the Import Wizard included with Altium Designer to open LIA files.