In the 68000 program in Figure 3.27, "in-line" code is used to read a line of characters and display them. Rewrite this program in the form of a main program that calls a subroutine named GETCHAR to read a single character and calls another subroutine named PUTCHAR to display a single character. The addresses INSTATUS and DATAIN are passed to GETCHAR in registers A0 and A1; and the main program expects to get the character passed back in register DO. The addresses OUTSTATUS and DATAOUT and the character to be displayed are passed to PUTCHAR in registers A2, A3, and DO, respectively. Any other registers used by either subroutine must be saved and restored by the subroutine using the processor stack whose pointer is register A7. Storing the characters in memory and checking for the end-of-line character CR is to be done in the main program.