crossover and their types-

Crossover:

Crossover is considered the most important genetic operator to improve the quality of solutions. The idea is to recombine useful features of parent chromosomes in a way that allows the new offspring to benefit from favourable bit segments of both parents. Crossover explores the most promising regions of search space in a more purposeful and efficient way than a purely random global search. The interaction of crossover and selection merely generates new variants in those regions which already demonstrated to contain well adapted solutions, i.e., it performs an appropriate exploitation of search space.
Instead of every parent chromosome, only a fraction of P selected at random according to the crossover probability Pc is subject to recombination. Typical values for the crossover rate are Pc ? [0.6,0.95].
Without crossover, the average fitness of the population,f,,, will climb until it equals the fitness of the fittest member,f,,. After this point it can only improve via mutation.