Update README.md

testing/README.md

@@ -2,9 +2,23 @@
 
 ## 1. introduction
 ### - 1.1 purpose
-- 1.1.1 basic explanation
+- 1.1.1 basic purpose
+  - This product is a kind of calculator that performs various operations related to fixed point number.
+  - For fixed-point arithmetic, c langauge's math library and type conversion are required.
 
+### 1.2 concept
+- 1.1.2 basic concept
+  - To operate several calculation for fixed-point numebr type casting is essential.
+  - Correct type conversion is very important in order to accurately calculate and avoid missing bits.
+- 1.1.3 concept of fixed-point number
+  - ![image](/uploads/0ae109d4300d11722c53531d1a9615ac/image.png)
+    - a. data types in computer langauge always have fixed length 
+    - b. in fixed point decimal point position of specific number should be fixed
+    - c. mean of s3132
+      - s(sign) / 31(interger) / 32(decimal point)
+      - first s bit is used for number's sign (+ or -)
+      - second 31bits are used to represent interger part
+      - third 32bits are used to represent decimal 
 
-### 1.3 concept
 ## 2. overall description
 ### - 2.1 product functions
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