How to Calculate the Square of 20 Using a Loop in Assembly Language

In this article, we will explore how to write an assembly language program to calculate the square of 20 by adding 20 to an accumulator 20 times using a loop. We will cover the basics of assembly language, the specific code example, and how to assemble and run the program.

Introduction to Assembly Language

Assembly language is a low-level programming language which has a one-to-one correspondence with the machine code instructions. It is often used for system-level programming, device drivers, and other tasks that require close interaction with the hardware. In this example, we will use x86 assembly language and demonstrate how to achieve a simple mathematical operation using loops.

Understanding the Calculation

The square of 20 is 400. To calculate this using a loop, we need to add 20 to an accumulator 20 times. This is known as the additive method for squaring a number in assembly language. Here's a brief explanation of the process:

Initialize an accumulator to zero. Add the number 20 to the accumulator 20 times. The result will be the square of 20, which is 400.

Assembly Code Example

Below is an example of how to implement this in x86 assembly language using NASM (Netwide Assembler).

Data Section

section .data num db 20 ; The number to be squared iterations db 20 ; Number of times to add

BSS Section

section .bss result resd 1 ; Reserve space for the result

Text Section

section .text global _start _start: xor eax, eax ; Clear the accumulator eax mov ecx, iterations ; Load the number of iterations into ecx loop_start: add eax, num ; Add the number 20 to the accumulator loop loop_start ; Decrease ecx and loop if ecx ! 0 mov [result], eax ; Store the result 400 in the reserved space ; Exit the program mov eax, 1 ; syscall: exit xor ebx, ebx ; return 0 int 80

Explanation

The code is divided into three sections:

Data Section: Defines the variables used in the program. BSS Section: Reserves space for the result. Text Section: Contains the main logic and instructions.

Here is a detailed breakdown of each section:

Data Section

num db 20 - This holds the number 20 to be squared. iterations db 20 - This holds the number of times we will add 20 to the accumulator.

BSS Section

result resd 1 - This reserves space to store the final result.

Text Section

global _start - Denotes the entry point of the program. xor eax, eax - Clears the accumulator register eax, which will store the result. mov ecx, iterations - Loads the number of iterations (20) into the loop counter register ecx. loop_start: - The starting point of the loop. add eax, num - Adds the number 20 (stored in num) to the accumulator eax. loop loop_start - Decrements the loop counter ecx and repeats the loop until ecx becomes zero. - Stores the result (400) in the reserved space. mov eax, 1, xor ebx, ebx, int 80 - Exits the program cleanly.

Assembling and Running the Code

To assemble and run the code, follow these steps:

Assemble the code using NASM: nasm -f elf32 -o square.o Link the object file with a tool like ld: ld -m elf_i386 -o square square.o Run the executable: ./square

The result will be stored in memory. You can inspect the result using a debugger or modify the code to print it out.

Conclusion

By understanding and implementing a simple loop in assembly language, you can achieve complex mathematical operations such as squaring a number. This example demonstrates the fundamentals of assembly language programming and provides a clear guide on how to write and run an assembly program.

Main Keywords

assembly language square calculation loop in assembly