Registers are what we call variables in a high level language. A MISP processor has 32 register named from 0 to 31 and distributed in the following way.
zero : It always contains the value 0
at, k0, k1 : Reserved for the assembler (at) and the operating
system (k0, k1). v0, v1 : v0 is used to set the value for a system call, and also it can be use in addition to v1 to store values returned from a system call or other procedure call a0 - a3 : Stores the values of the arguments passed to a system or procedure call. t0 - t9 : Temporary registers whose values are not preserved after a function call. s1 - s7 : Temporary registers whose values are preserved during a function call sp : Stack pointer. It points to the “top” of the stack.
fp : Frame pointer. It is used to save the value of a frame in a
function call. gp : Global pointer. It points into the middle of a 64k block of
memory in the heap that holds constant and global variables. ra : Return address. It is use to save and restore the address
before and after a function call.