# 8086 program to subtract two 16-bit numbers with or without borrow

**Problem –** Write a program to subtract two 16-bit numbers where starting address is **2000** and the numbers are at **3000** and **3002** memory address and store result into **3004** and **3006** memory address.

**Example –**

**Algorithm –**

- Load 0000H into CX register (for borrow)
- Load the data into AX(accumulator) from memory 3000
- Load the data into BX register from memory 3002
- Subtract BX with Accumulator AX
- Jump if no borrow
- Increment CX by 1
- Move data from AX(accumulator) to memory 3004
- Move data from CX register to memory 3006
- Stop

**Program –**

Memory | Mnemonics | Operands | Comment |
---|---|---|---|

2000 | MOV | CX, 0000 | [CX] <- 0000 |

2003 | MOV | AX, [3000] | [AX] <- [3000] |

2007 | MOV | BX, [3002] | [BX] <- [3002] |

200B | SUB | AX, BX | [AX] <- [AX] – [BX] |

200D | JNC | 2010 | Jump if no borrow |

200F | INC | CX | [CX] <- [CX] + 1 |

2010 | MOV | [3004], AX | [3004] <- [AX] |

2014 | MOV | [3006], CX | [3006] <- [CX] |

2018 | HLT | Stop |

**Explanation –**

**MOV**is used to load and store data.**SUB**is used to subtract two numbers where their one number is in accumulator or not.**JNC**is a 2-bit command which is used to check whether the borrow is generated from accumulator or not.**INC**is used to increment an register by 1.**HLT**is used to stop the program.**AX**is an accumulator which is used to load and store the data.**BX, CX**are general purpose registers where BX is used for storing second number and CX is used to store borrow.

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