diff --git a/assembly_code/chp1_21.asm b/assembly_code/chp1_21.asm
new file mode 100644
index 0000000..03af016
--- /dev/null
+++ b/assembly_code/chp1_21.asm
@@ -0,0 +1,18 @@
+; solution developed by https://github.com/DarkShadowFT/
+
+
+; Write a program in assembly language that calculates the square of 
+; six by adding six to the accumulator six times.
+[org 0x0100]
+
+mov ax, 6                   ; moves six to the acculumator
+
+add ax, 6                   ; adding six to the acculumator until ax=36
+                            ; (or 24 in hex)
+add ax, 6
+add ax, 6
+add ax, 6
+add ax, 6
+
+mov ax, 0x4c00              ; exit.
+int 0x21