Lesson 2: Data Interchange Formats — JSON and XML

When two systems exchange data, they must agree on a format both can read — a data interchange format. A Java banking system and a Python mobile backend cannot share raw objects in memory; they exchange text that each side can parse. The two formats you must master are JSON (JavaScript Object Notation) and XML (eXtensible Markup Language). JSON looks like nested key-value pairs: {"name": "Ana", "course": "BSIT"}. XML wraps data in tags: <student><name>Ana</name></student>. JSON dominates modern web APIs because it is lighter and maps directly to objects in most languages; XML is still everywhere in enterprise and government systems (electronic invoices, bank files, old web services). Being able to read, write, and convert between both is a core exam skill and a daily task in real integration work.

JSON has only a few building blocks, which is why it is so popular. Values can be strings, numbers, booleans (true/false), null, arrays, or objects. Objects are unordered collections of key-value pairs in braces {}; arrays are ordered lists in brackets []. A student record with grades might look like: {"student_id": "2024-00123", "grades": [{"subject": "IPT1", "grade": 1.75}]}. Rules to remember for exams: keys must be double-quoted strings; no trailing commas; no comments allowed. In Python, json.loads() turns a JSON string into dictionaries and lists, and json.dumps() goes the other way — this pair is called deserialization and serialization. Almost every REST API you will ever call (payment gateways, weather services, government portals) sends and receives JSON, so fluency here pays off in every later lesson.