diff --git a/index.js b/index.js
index 511981f..1fd1306 100644
--- a/index.js
+++ b/index.js
@@ -603,6 +603,7 @@ class TICrypto {
    * @param {*} [{ coin }={}]
    * @return {*}
    * @memberof TICrypto
+   * position 就是通常所说的 PubKeyHash，出现在比特币交易的锁定脚本里
    */
   static pubkey2position(pubkey, { coin } = {}) {
     // tic, btc, eth 的 position 都是 20节=40字符的。
@@ -713,16 +714,18 @@ class TICrypto {
    * @static
    * @return {*}
    * @memberof TICrypto
+   * 地址和PubKeyHash(即position)之间能互相转化
    */
   static address2position() {
-    if (/^0x[\da-fA-F]{40}$/.test(address)) {
+    if (/^0x[\da-fA-F]{40}$/.test(address)) { // ETH
+      // todo: 如果是大小写敏感的，进行有效性验证
       return address.toLowerCase()
-    } else if (/^[123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz]{26,34}$/.test(address)) {
+    } else if (/^[123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz]{26,34}$/.test(address)) { // BTC
       let hex = this.b58c2hex(address)
       if (hex) {
         return hex.slice(2) // 去除网络前缀
       }
-    } else if (/^[Tt][0-9a-zA-Z\-_]{31}$/.test(address)) {
+    } else if (/^[Tt][0-9a-zA-Z\-_]{31}$/.test(address)) { // TIC
       // 格式合法
       let hex = this.b64u2hex(address)
       let [all, prefix, position, checksum] = hex.match(/^([\da-fA-F]{2})([\da-fA-F]{40})([\da-fA-F]{6})$/)