1958: Magnetic tape
Operation
The data storage on a magnetic tape carried by the magnetization of an appropriately coated tape. Small compass needles were aligned. Binary information is stored permanently until the next realignment of the needles. Basically, the band on a read-write head is passed. The read-write head is a metal ring that is open on one side. It is (seen in picture above), a small current to the non-open side of the ring in the form of a coil creates a magnetic field thereby (indicated by red in the picture) at the opening. This is done by induction. For writing and reading can be used two different methods. First, the linear method in parallel to the first written over the entire length of tape running traces sequentially. The tape is moved in one direction until the end under the magnetic head over. When the end of the tape is reached, it changes direction and the band runs through to the other end under the magnetic head. This method is also called serpentine.
The most important linear methods are: Linear Tape Open (LTO), digital linear tape (DLT), Super DLT and Advanced Digital Recording (ADR).
In contrast, in the helical scanning system described the tape diagonally from corner to corner. The magnetic head is inclined to the band here.
The main helical scan methods are: Advanced Intelligent Tape (. AIT), Mammoth tapes, digital audio tape (DAT) and Digital Tape Format (DTF). Popular tape formats are 4 mm, 8 mm, 1⁄4 inch (6.2 mm) and 1⁄2 inch (12.5 mm).
