Different data types and how to initialize them

Let me break down the different data types and how to initialize them with simple mental models and code snippets.

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1. Normal Variables

Think of them as boxes holding values.

int a = 10;        // integer
float f = 3.14;    // float
char c = 'A';      // single character

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2. Arrays

An array is a collection of boxes of the same type, placed in sequence.

int arr[5] = {1, 2, 3, 4, 5};   // integer array
char str1[] = "Hello";          // string as char array (null-terminated)
char str2[6] = {'H','e','l','l','o','\0'}; // same thing explicitly

Rule: If you don’t fully fill an array, remaining elements are 0.

int arr2[5] = {1,2};  // arr2 = {1,2,0,0,0}

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3. Pointers

A pointer is a box that stores the address of another box.

int x = 10;          
int *p = &x;        // pointer to int
printf("%d", *p);   // dereference → prints 10

Trick:

• & = “address of”
• * = “value at that address”

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4. Pointer + Array

Arrays and pointers are closely related.

int arr[3] = {10,20,30};
int *p = arr;       // points to arr[0]

printf("%d", *(p+1)); // prints 20

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5. Strings (char arrays vs pointers)

char str1[] = "Hello";     // stored in modifiable array
char *str2 = "Hello";      // stored in read-only memory (can’t change chars)

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6. Structs

A struct is a custom data type grouping multiple variables.

struct Point {
    int x;
    int y;
};

struct Point p1 = {10, 20};   // initialize

With pointers:

struct Point p2 = {30, 40};
struct Point *ptr = &p2;
printf("%d", ptr->x);   // prints 30

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Mental model:

• Normal variable → box with value
• Array → row of boxes
• Pointer → box with an arrow to another box
• String → char array ending with '\0'
• Struct → box containing multiple labeled smaller boxes

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