Abstract: A ballpoint pen system having a slidable pen cap. A ballpoint ink cartridge disposed inside a pen housing has a ballpoint tip protruding out of a pen housing anterior aperture. The pen cap is disposed on a pen housing anterior end for capping the ballpoint tip. At least one linear pen cap through-slot is disposed through a pen cap side surface. At least one raised stopper located on the pen housing near the pen housing anterior end is disposed through the through-slot of the pen cap such that linearly sliding the pen cap causes the pen cap to move longitudinally relative to the pen housing. Sliding the pen cap to an extended position causes the pen cap to cover the ballpoint tip. Sliding the pen cap to a retracted position causes the ballpoint tip to protrude from the pen cap anterior aperture.