# Instruction Set used in SIC/XE

Prerequisite – Instruction Set used in simplified instructional Computer (SIC)

As SIC/XE is upward compatible with respect to SIC, therefore all the instructions in SIC are also used in SIC/XE. The instructions unique to SIC/XE are:

MNEMONIC | OPERAND | OPCODE | EXPLANATION |
---|---|---|---|

ADDR | R1, R2 | 90 | R2 = R2 + R1 |

CLEAR | R1 | 04 | R1 = 0 |

COMPR | R1, R2 | A0 | compares R1 and R2 |

DIVR | R1, R2 | 9C | R2 = R2 / R1 |

LDB | M | 68 | B = M |

LDS | M | 6C | S = M |

LDT | M | 74 | T = M |

MULR | R1, R2 | 98 | R2 = R2 * R1 |

RMO | R1, R2 | AC | R2 = R1 |

SHIFTL | R1, n | A4 | left shifts R1 n times |

SHIFTR | R1, n | A8 | right shifts R1 n times |

STB | M | 78 | M = B |

STS | M | 7C | M = S |

STT | M | 84 | M = T |

SUBR | R1, R2 | 94 | R2 = R2 – R1 |

TIXR | R1 | B8 | X = X + 1; compares X and R1 |

Here,

M stands for Memory

R1 and R2 are registers (A, B, S, T)