Question

Why ccp structure is also called fcc structure ?

Answer 1

CCP are one of the forms in which a cubic lattice is arranged and FCC is one of the types of unit cells(in general). When we place the atoms in the octahedral voids the packing is of ABCABC.. type.This is known as CCP. Now sometimes we also call it as face centered closed structure (FCC)But remember FCC can also stand for the unit cell (Face centered cell).
packing efficiency of FCC and CCP are same that iscequal to 74%. That is the reason ccp structure is also called fcc structure.