1. A context switch method comprising: converting a state of multiple register files to be in any one of a prefetch state, a current state, and a store state when a context switch occurs; wherein, in the prefetch state, determining a memory address to read a predicted next task context to be subsequently performed, in the current state, performing a task with a task context of a register file, and in the store state, storing the register file in a memory to identify a next task context to be subsequently performed, wherein when a context switch occurs, the converting of the state of the multiple register files to be in any one of the prefetch state, the current state, and the store state comprises: determining, when the context switch occurs, whether a next task context switch to be subsequently performed is stored in the store state of the multiple register files; and converting, when the determination indicating that the next task context is stored in the store state, the register file in the store state into a current state and the register file in the current state into a store state.