1. An electronic apparatus comprising: a nonvolatile memory that includes a plurality of programs including i) a start processing program needed for a start process, ii) an update executing program, and iii) a function executing program for executing a function, and header information, wherein: the header information includes a header information identifier, a header information size, information of the plurality of programs, and information of a head position of each of the plurality of programs; and the information of the plurality of programs includes an identifier for identifying each of the plurality of programs and size of each of the plurality of programs; a volatile memory that includes a plurality of new programs including a new start processing program, a new update executing program, and a new function executing program; and a processor that rewrites the plurality of programs in the nonvolatile memory with the plurality of new programs, thereby accompanying extension of the function; wherein the processor: executes a boot process when a power supply is turned on; reads the header information in the nonvolatile memory; confirms the size and an arrangement order of the plurality of programs in the nonvolatile memory; writes the plurality of new programs to the volatile memory from at least one of an SD card and a sever via a network; writes a new header information in the volatile memory, wherein the new header information includes information of an arrangement order of the plurality of new programs in the volatile memory that is reverse of the arrangement order of the plurality of programs in the nonvolatile memory; writes at first the new start processing program and the new update executing program to the nonvolatile memory from the volatile memory; writes the new header information to the nonvolatile memory from the volatile memory, when completing the writing of the new start processing program and the new update executing program to the nonvolatile memory; and writes the new function executing program to the nonvolatile memory from the volatile memory, when completing the writing of the new header information to the nonvolatile memory; wherein the processor further: writes the plurality of new programs to the volatile memory from at least one of the SD card and the sever via the network, according to the header information, the start processing program and the update executing program which have been remained as written in the nonvolatile memory, if the power supply is turned off while the writing of the new start processing program and the new update executing program; writes the plurality of new programs to the volatile memory from at least one of the SD card and the sever via the network, according to the start processing program and the update executing program which have been remained as written in the nonvolatile memory, if the power supply is turned off while the writing of the new header information; and writes the plurality of new programs to the volatile memory from at least one of the SD card and the sever via the network, according to the new header information, the new start processing program and the new update executing program which have been remained as written in the nonvolatile memory, if the power supply is turned off while the writing of the new function executing program.