/* Main instruction fetch/decode loop */

while (reason == 0) {                                   /* loop until halted */

    // clean SIMH loop exit code here

    // SIMH clock queue code here

    // handle hardware device interrupt here

    // handle SIMH breakpoint here

    // perform instruction fetch here

/* Instruction decoding happens below */

switch ((IR >> 7) & 037) {                              /* decode IR<0:4> */

/* Opcode 0, AND */

    case 000:                                           /* AND, dir, zero */
	// Handle AND, direct, zero page
	break

    case 001:                                           /* AND, dir, curr */
	// Handle AND, direct, current page
        break;

    case 002:                                           /* AND, indir, zero */
	// Handle AND, indirect, zero page
        break;

    case 003:                                           /* AND, indir, curr */
	// Handle AND, indirect, current page
        break;

/* Opcode 1, TAD */

    // same structure as AND: direct / indirect with zero / current page
        break;

/* Opcode 2, ISZ */

    // same structure as AND: direct / indirect with zero / current page
        break;

/* Opcode 3, DCA */

    // same structure as AND: direct / indirect with zero / current page
        break;

/* Opcode 4, JMS */

    // same structure as AND: direct / indirect with zero / current page
    // but also modifications to emulate timeshare control
        break;

/* Opcode 5, JMP */

    // same structure as JMS: direct / indirect with zero / current page
    // including modifications to emulate timeshare control
        break;

/* Opcode 7, OPRs */

    // handle all Operate group 1, 2, 3 standard, and 3 EAE variations
    // group 3 EAE includes Mode A and Mode B emulation
    break;

/* Opcode 6, IOT */

    // handle all IOTs including timeshare control card

/* ---PiDP add--------------------------------------------------------------------------------------------- */

    // Update the front panel with this instruction's final state.

/* ---PiDP end---------------------------------------------------------------------------------------------- */


    }                                                   /* end while */