5. C Structures, Unions & Enums
Comprehensive Guide: User-defined composite data types, struct member access, arrow operator -> & memory unions
Module 1: C Structures (struct) & Arrow Operator
Grouping variables of different data types under a single user-defined record type.
🇬🇧 English Definition
A structure is a user-defined composite data type in C that allows grouping variables of different data types under a single name.
🇮🇳 Hinglish Definition
Structure se hum naya custom data type bana sakte hai jisme alag-alag types (int, float, char) ka data ek saath grouping me reh sakta hai.
Core Concepts & Rules
- Member access using dot operator: student1.id.
- Structure pointer access using arrow operator: ptr->id.
- Memory size of struct equals sum of member sizes (plus alignment padding).
🔍 Line-by-Line Code Breakdown
- Line 1-4: Define struct Student with fields id and marks.
- Line 7: Instantiate struct Student s1 = {101, 98.5}.
- Line 8: Declare structure pointer ptr pointing to &s1.
- Line 9-10: Print fields using arrow operator ptr->id and ptr->marks.
struct Student {
int id;
float marks;
};
int main() {
struct Student s1 = {101, 98.5f};
struct Student *ptr = &s1;
printf("Student ID: %d\n", ptr->id);
printf("Marks: %.1f\n", ptr->marks);
return 0;
}Module 2: Unions (union) vs Structures Memory Allocation
Sharing memory space between different fields to minimize RAM footprint.
🇬🇧 English Definition
A union is a special data type that allows storing different data types in the SAME memory location, allocating size equal to its largest member.
🇮🇳 Hinglish Definition
Union me saare members EK HI memory location share karte hai. Memory size sabse bade member ke barabar hoti hai.
Core Concepts & Rules
- Only ONE member of a union can contain a valid value at any given time.
- Saves RAM memory in embedded hardware systems.
🔍 Line-by-Line Code Breakdown
- Line 1-4: Define union Data with int i and float f sharing same RAM memory.
- Line 7: Assign d.i = 50 and print.
union Data {
int i;
float f;
};
int main() {
union Data d;
d.i = 50;
printf("Union Integer Value: %d\n", d.i);
return 0;
}