What is the smallest monetary unit in Tezos, and where is it defined in the code?
Currently 1 tez (1 XTZ) is divisible to six decimal places, and the smallest unit is called a micro tez (mutez).
1 tez = 1,000,000 micro tez
In code it is referred to as
one_mutez and it is defined in src/proto_013_PtJakart/lib_protocol/tez_repr.ml:
(* all other constant are defined from the value of one micro tez *) let one_mutez = Tez_tag 1L let max_mutez = Tez_tag Int64.max_int let mul_int (Tez_tag tez) i = Tez_tag (Int64.mul tez i) let one_cent = mul_int one_mutez 10_000L let fifty_cents = mul_int one_cent 50L (* 1 tez = 100 cents = 1_000_000 mutez *) let one = mul_int one_cent 100L