title: Concept of bank registers in ARM
body: <p>I am new to <code>ARM</code> and bit confused on the concept of Bank registers.<code>Arm</code> related docs say
  that Each mode has its own set of banked register except user mode .My confusion is that Do
  every mode has register from <code>r0-r15</code>+banked register.If so. then <code>FIQ</code> mode has highest number of register available to it which is 23 total registers .</p>
  
  <p>Also,it is said about <code>ARM</code> register out of total 37 register ,20 are register are hidden from program at different times.what does it mean??</p>