LEF
Beginner
A computer file that describes the outline and plug points of each building block, but not what’s inside.
Novice
Library Exchange Format: text files that describe the building blocks without their insides. A technology LEF lists the manufacturing layers and their rules; cell and macro LEFs give each block’s size, the shapes of its pins, and the areas it blocks.
Expert
An abstract view: SIZE, SYMMETRY, CLASS (CORE, BLOCK, PAD, ENDCAP…), PIN shapes by layer, and OBS (obstructions). Floorplanning uses macro LEF for footprints, pin sides and blocked layers, and tech LEF for placement sites, track pitches and layer directions.