Introduction
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Maps are [:ref:`D4.06.05 <D4.06.05>`] "constant by element" fields. Formally, a map is a data structure that maps cells and occurrences of the same size (for example MATER for material characteristics).

Maps are often used to store data affected by the user on "areas" of their mesh (commands AFFE_CHAR_MECA, AFFE_MATERIAU, AFFE_CARA_ELEM,...). These fields can then be used as "inputs" for elementary calculations [:external:ref:`D3.02.01 <D3.02.01>`].

Four routines are available for programmers to build CARTES:


* MECACT: to create a constant map.


* ALCART: to "allocate" a card.


* NOCART: to write a couple (size, affected_zone) in a map.


* TECART: to "finish" a card (optional operation).