History and Development The primary means of computer storage, before the introduction of magnetic storage, were punch cards. These were paper cards in which holes were punched to indicate binary data invented by Herman Hollerith in the late 19th century. In June 1949, a group of scientists and engineers at IBM began working on creating a new storage device that would soon revolutionize the industry. May 21, 1952 marked the transition from punched card calculators to electronic computers when IBM introduced the IBM 726 Tape Unit [1]. It was used to store data in IBM's first commercial scientific computer intended to help the US Army design aircraft [2]. Four years later, IBM made the first computer disk storage system: the 305 RAMAC drive. Although this drive could only store 5 MB of data, the information could be stored directly at any location on the disk's surface without having to read all the information in between, as was the case with magnetic tapes. This ability to access random locations had a very important effect on computer performance and allowed data to be stored and retrieved much faster than tapes. The next 60 years saw tremendous advancement in magnetic storage, from a variety of hard drives to portable storage such as cassettes, floppy disks, and zip drives. Today, even 3TB of data can be stored on tiny 3.5-inch drives. All this was possible thanks to electromagnetism and the magnetic properties of ferromagnetic materials such as iron oxides[add part about magnetism]In 1819, a Danish physicist Hans Christian Oersted was preparing his materials for an experiment when he made a brilliant observation . He noticed that when a compass needle was brought close to a wire that conducted an electric current, the n... half of the paper... of the head. As a result, the magnetic field due to the head polarizes the magnetic particles passing directly through the medium and aligns them with its field. Based on the flow of electric current through the coils, the polarity of the head field and the field induced in the magnetic medium changes its polarity. As a result, when the magnetic field passes through the medium, the particles located just below the headspace tend to align in the same direction as this field. Once the particles' individual magnetic dipoles are aligned, they no longer cancel out, and a net magnetic field is observed in that region. Many magnetic particles now work together to produce a cumulative field with the same direction. Due to the hysteresis properties of ferromagnetic materials, individual particles maintain their magnetic dipoles and net field.