6.1 C Struct

1. Introduction to `struct`

A struct in C is a user-defined data type that allows grouping of variables of different types under a single name. It is used to represent a collection of related data.

Example:

struct Person {
    char name[50];
    int age;
    float height;
};

In this example, struct Person defines a structure with three members: name (a string), age (an integer), and height (a float). You can then create variables of type struct Person and access their members.

Usage:

struct Person person1;
person1.age = 25;
person1.height = 5.9;
strcpy(person1.name, "Alice");

`struct` Similar to Class ?

a struct in C is somewhat similar to a class in Python or Java, but with key differences:

Similarities:

Both group related data together.
You can access individual members (or attributes) using dot notation.

Differences:

No Methods: A struct in C only holds data (variables). It doesn’t have methods (functions) like a class in Python or Java.
No Encapsulation: C struct members are always public, so there’s no concept of private or protected access modifiers.
No Inheritance: C struct doesn’t support inheritance, while classes in Python and Java do.
Memory Management: C doesn’t have automatic memory management (like garbage collection in Java or Python). You must manage memory manually using malloc and free if you’re using pointers inside a struct.

In short, while both are used to represent composite data types, classes in Python or Java are more powerful and feature-rich.

2. Syntax

2.1 Basic Usecase

/* Declaration of the struct */
struct Person {
char zName[10];
int iAge;
} p2, p4;

/* p2, p4 are variable of type `struct Person` */

/* Can create more varaibles out of the type `struct Person` */
struct Person p1;

2.2 Anonymous Struct

// Declaration of an anonymous struct and creating a variable  at the same time
struct { /* <tag_name> is optional */
char zName[4];
int iAge;
} p1, p2;

...

struct <???> p3;
/*  ERR: Cannot create a variable later using the anonymous struct above.
    This is because anonymous struct does not have a tag name
 */

2.3 `typedef` a `struct`

/* Declaration of the struct */
typedef struct { /* <tag_name> is optional */
char zName[10];
int iAge;
} PersonType;

/* Create a variable out of the datatype 'PersonType' */
PersonType p1;

strcpy(p1.zName, “Nadith”);
p1.iAge = 30;

PersonType p2;

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