AIM :Write a program to add and subtract two 16-bit numbers with/ without carry using 8086

Objective:

1. To understand working of 8086 Based System.
2. To draw flowchart of the 16-bit Addition
3. To develop and execute program,
4. To verify the result of two 16-bit long number.

System Requirement :

• 8086 Trainer Kit with Key Board

Setting up the Trainer Kit:

1. Ensure that standard IBM PC/AT system keyboard is connected
2. System is Powered ON
3. Student has a handy opcode table for programming
4. Use data Address as :
   1. For Program Code

segment address : 1000            Offset address : 0200

1. For Data

segment address 0000               offset address : 1300

Flowchart to Add two 16-bit numbers:

Algorithm:

1. Start
2. Initialize the BX, and SI Registers
3. Read the contents of the memory pointer by SI register in register AX
4. Increment the SI register content
5. Read the contents of the memory pointer by SI register in register BX
6. Add content of AX and BX
7. Increment the SI register content
8. Check if carry is generated
9. If yes increment BL, SI and save carry
10. End of the program

Explanation of the Code for Adding two 16-bit numbers:

Explanation of the Code for Adding two 16-bit numbers:

Execution of Program on 8086 Kit

Address Map for DATA

Executing The Program

Verification of Result

Subtraction of two 16-bit numbers

** NOTE: For writing an ALP to subtract two 16-bit numbers. Programming logic is exactly similar to the one for adding as given above. For subtracting use SUB AX, BX, the hex code for this is 2AC3. Replace line number 7  as:

7.   1000: 020A      2A C3   SUB AX, BX     ;result  AX = AX – BX

Experiment-1 Viva Question:

Q.1 Why two address Segment Address and Offset is used)

Answer: Memory of 8086 microprocessor is divided into different segment. Each segment has its base address and the all address within that segment are the offsets. The segment address and the offset address combined together are used to provide 20-bit physical address

Q.2 What is the purpose of CLC mnemonic code

Answer: CLC stands for clear the carry flag. If for some reason the carry flag was previously set, this action will reset the carry flag to zero.

Q.3 What is the use of BX register in this experiment

Answer: When two numbers are added, carry may generate whose status is saved in flag register. A register BX is used to keep the count of the carry. If the carry get generated program jums to a location 0214 to and the register content is incremented. The carry (Content of BL) is then saved in memory pointed by SI register.

Q.4 What is the SI register used in this program

Answer: SI register is used as a source pointer register. It contains the address of the source data i.e. 0000:1300. The microprocessor reads the data pointed by the SI register content (Address)

Q.5 What is the purpose of the instruction MOV AX, [SI]?

Answer: [SI] means the content at the memory location whose address is given in register SI.  So, MOV AX, [SI] will transfer content of memory location given in SI into AX register