Start adding things to fintech section

_sidebar.md

@@ -21,6 +21,7 @@
     - [AWS](categories/devops/aws.md)
 - [Web](categories/web.md)
 - [IoT](categories/iot.md)
+- [Fintech](categories/fintech.md)
 - [Success Team Work](categories/team-work.md)
 - [Uncategorised](categories/uncategorised.md)
 - English

categories/fintech.md

@@ -0,0 +1,45 @@
+# Fintech(Financial technology)
+
+## ISO8583 message
+
+### A example
+
+```
+02004200040000000002161234567890123456060
+9173030123456789ABC1000123456789012345678
+90123456789012345678901234567890123456789
+0123456789012345678901234567890123456789
+```
+Where:
+
+```
+  0200 - MTI (Message Type Indicator),
+  4200040000000002 - primary bitmap,
+  161234567890123456 - field 2, the first 2 digits: 16, is length indicator
+  0609173030 - field 7,
+  123456789ABC - field 22,
+  012345678901234567890123456789012345678901234567890\
+  1234567890123456789012345678901234567890123456789 - field 63.
+```
+
+### Definition
+
+ISO8583 message is used in bank or financial institutes card-originated transactions. But sometime, those not card-originated transactions also use ISO8583.
+
+### Typical Parts
+
+Typical Fields an ISO8583 message
+A typical message might include such fields:
+```
+MTI - Message Type Indicator.
+Bit 2 - Primary Account Number (PAN)
+Bit 3 - Processing Code
+Bit 7 - Date and Time of transmission
+Bit 11 - Audit Code
+Bit 12 - Local time transaction
+Bit 13 - Local transaction date
+Bit 32 - Identification code of the institution of acquisition
+Bit 38 - The authorization code in response
+Bit 39 - Response Code
+Bit 49 - Currency code of transaction
+```