Addition of two 16-bit numbers

code.asm

data segment 
a dw 0202h
b dw 0408h
c dw ?
data ends


code segment
assume cs:code, ds:data
start:

mov ax, data
mov ds, ax
mov ax, a 
mov bx, b
add ax, bx
mov c, ax

int 3

code ends
end start

flowchart.pgn

Understand the code

Data Segment

a dw 0202h: This line declares a 16-bit word variable named a and initializes it with the hexadecimal value 0202.

b dw 0408h: Similarly, this declares a 16-bit word variable b and initializes it with the hexadecimal value 0408.

c dw ?: This declares a 16-bit word variable c but does not initialize it. It will store the result of the addition operation.

Code Segment

mov ax,data: This instruction moves the address of the data segment into the AX register.

mov ds,ax: This sets the Data Segment (DS) register to the value in AX, effectively making the data segment accessible for data operations.

mov ax,a: This moves the value of a (0202h) into the AX register.

mov bx,b: This moves the value of b (0408h) into the BX register.

add ax,bx: This adds the contents of BX to the contents of AX. The result (060Ah) is stored in AX. ; mov c,ax: This moves the result from AX to the variable c.

int 3: This is a breakpoint instruction that causes the program to halt, allowing for debugging and inspection of registers and memory.

Overall Functionality

The code performs the following steps:

Initialization: Sets up the data segment and initializes variables a and b. ; Addition: Loads the values of a and b into registers AX and BX, respectively. Adds the two values and stores the result in AX.

Result Storage: Stores the result from AX into the variable c.

Program Termination: Halts the program execution using the int 3 instruction.

In essence, this code adds two 16-bit hexadecimal numbers (0202h and 0408h) and stores the result (060Ah) in the variable c.