  Cosmic rays with energy exceeding ~ 10^{18} eV are referred to as ultra-high
energy cosmic rays (UHECRs). Monte Carlo codes for extensive air shower (EAS)
simulate the development of EASs initiated by UHECRs in the Earth's atmosphere.
Experiments to detect UHECRs utilize EAS simulations to estimate their energy,
arrival direction, and composition. In this paper, we compare EAS simulations
with two different codes, CORSIKA and COSMOS, presenting quantities including
the longitudinal distribution of particles, depth of shower maximum, kinetic
energy distribution of particle at the ground, and energy deposited to the air.
We then discuss implications of our results to UHECR experiments.
