diff --git a/README.md b/README.md
index f6e150a..d6869a9 100644
--- a/README.md
+++ b/README.md
@@ -2,4 +2,19 @@
 
 **This project provides a graphical interface that users can use to simulate the output from combinations of several inputs.**
 
-aaa
+* function of each button
+  1. `IN`: Generate an input block. Double click it to select the type of input.
+  2. `OUT`: Generate an output block.
+  3. `AND`: Generate an AND block, which performs function of logic and.
+  4. `OR`: Generate an OR block, which performs function of logic or.
+  5. `NOT`: Generate a NOT block, which performs function of logic not.
+  6. `Function`: Generate a function block. Double click it to select the type of operation to perform on two specific inputs.
+  7. `Line`: Enter line mode in which users can link blocks.
+  8. `Simulate`: Select a specific output block and simulate it.
+  9. `Grid`: Display the grid.
+  10. `Lock`: Turn on the lock mode to align the block to the grid.
+  11. `背景圖片`: Set the background image.
+  12. `背景顏色`: Set the background color.
+  13. `Open`: Load simulation file.
+  14. `Save`: Save simulation file.
+