In the C and C++ programming languages, #pragma once is a non-standard but widely supported preprocessor directive designed to cause the current source file to be included only once in a single compilation.
During sexual reproduction, fertilization of the ovum (n, 23 chromosomes) by the sperm (n, 23 chromosomes) restores the diploid number and creates a zygote (2n, 46) (awww..) that divides and grows by mitosis to form a multicellular human.
Meiosis reduces the number of chromosomes. Eggs and sperm are haploid (1n) cells, which contain one set of all chromosomes, and products of meiotic division. Sexual life cycles have both haploid and diploid stages. During fertilization, or syngamy, the fusion of two haploid gametes results in a diploid (2n) zygote, which contains two sets of chromosomes.