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Basics of C Programming โ Self Study Notes What is C? C is one of the oldest and most powerful programming languages, created in the 1970s. Think of C as the blueprint language โ almost every modern language (Python, Java, JavaScript) borrowed ideas from it. Learning C is like learning to drive a manual car: harder at first, but you understand how the engine works. Variables โ Labelled Boxes in Your Brain A variable is a named storage location in memory. Think of it like a labelled jar in your kitchen โ the label is the variable name, and whatever is inside is its value. int age = 25; Jar analogy: The jar is labelled age. Inside it, you've placed the number 25. You can empty it and refill it with a different number anytime. Rules for naming variables:
- Must start with a letter or underscore ( _ )
- No spaces, use _ instead (e.g., student_name )
- Case-sensitive: Age and age are two different jars Data Types โ The Type of Jar You Use Not all jars are the same. You wouldn't store soup in a sugar dispenser. In C, data types tell the computer what kind of value the variable will hold โ and how much memory to reserve. 1. int โ Whole Numbers Real world: Number of students in a class, your age, a house number.
int students = 42; int floors = 3; Imagine counting floors in a building โ you say 3, not 3.5. Memory used: 4 bytes (can hold roughly โ2 billion to +2 billion)
2. float โ Decimal Numbers (Single Precision) Real world: Price of groceries, your temperature reading, a petrol bill. float price = 89.99; float temperature = 36.6; A thermometer shows 36.6ยฐC โ not just 36. That decimal matters. Memory used: 4 bytes (~6โ7 decimal digits of precision) 3. double โ Decimal Numbers (High Precision) Real world: Scientific calculations, GPS coordinates, bank balances. double distance = 384400.756; // Distance to the Moon in km double balance = 1000250.8875; When NASA calculates a rocket's path, they can't round off. Every decimal counts. Memory used: 8 bytes (~15 decimal digits of precision) 4. char โ A Single Character Real world: A grade on your report card, a gender field (M/F), a single letter in a word. char grade = 'A'; char initial = 'R';
This is like a student's profile card โ age, marks, fees, and grade all stored neatly in their own labelled compartment. Quick Reference Table Data Type Real World Example Format Specifier Size int Number of chairs %d 4 bytes float Petrol price %f 4 bytes double Bank account balance %lf 8 bytes char Blood group (A, B) %c 1 byte Key Takeaways
- A variable is a named container โ pick names that describe what's inside
- Choose the right data type for the right job โ don't use a double when an int will do
- C is case-sensitive โ Score and score are completely different variables
- Every C program starts with main() and needs #include to print output
