EXTERNAL MEMORY

MAGNETIC DISK:


• Circular platter constructed of nonmagnetic material, called the substrate, 
coated with a magnetizeable material 

• Substrate was traditionally aluminum or aluminum alloy 

• Substrate now glass 

    o Improved surface uniformity – increased reliability 

    o Reduction in surface defects – reduce read/write errors 

    o Support lower fly heights 

    o Greater ability to withstand shock and damage 




Magnetic Read and Write Mechanisms 

• Data recording and retrieval via a conducting coil named the head 

• Read and write heads may be combined or separate

• Read/write operations – the head is stationary while the platter rotates beneath it 

• Write 

     o Current flowing through a coil produces a magnetic field 

     o Pulses are sent to the head 

     o Magnetic patterns are recorded on the surface below

POSTED BY:  HAZYANTY SHAHIRA ABD. HALIM