Architect Zone in C

1. Dynamic Memory Allocation

Dynamic Memory Allocation is a process in C where memory is allocated during runtime (i.e., while the program is running), rather than at compile time.

It allows you to allocate memory at runtime using functions from <stdlib.h>.

Functions:

Function	Purpose
malloc()	Allocates a block of memory
calloc()	Allocates & initializes memory
free()	Frees previously allocated memory

📘 Example using malloc:

cCopyEdit#include <stdio.h>
#include <stdlib.h>
int main() {
    int *ptr;
    ptr = (int*) malloc(5 * sizeof(int));
    if (ptr == NULL) {
        printf("Memory not allocated.\n");
        return 1;
    }
    for(int i = 0; i < 5; i++) {
        ptr[i] = i + 1;
        printf("%d ", ptr[i]);
    }
    free(ptr); // Deallocating memory
    return 0;
}

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2. 🔁 Advanced Pointers

✅ Pointer to Pointer:

It stores the address of another pointer.

cCopyEditint a = 10;
int *p = &a;
int **pp = &p;
printf("%d\n", **pp);  // Output: 10

✅ Function Pointers:

Stores address of a function. Useful in callbacks and implementing plug-in behavior.

📘 Example:

cCopyEdit#include <stdio.h>
void greet() {
    printf("Hello from function pointer!\n");
}
int main() {
    void (*fp)() = greet;
    fp();  // Call function using pointer
    return 0;
}

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3. 📂 File Handling in C

File I/O allows reading and writing to files.

✅ Common functions:

• fopen(), fclose()
• fprintf(), fscanf()
• fread(), fwrite()
• fgets(), fputs()

📘 Example: Write and read from a file

cCopyEdit#include <stdio.h>
int main() {
    FILE *fp;
    fp = fopen("data.txt", "w");
    fprintf(fp, "Welcome, Keshab!");
    fclose(fp);

    char content[50];
    fp = fopen("data.txt", "r");
    fgets(content, 50, fp);
    printf("File content: %s\n", content);
    fclose(fp);
    return 0;
}

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4. ⚙️ Bitwise Operators

Used for bit-level operations (speedy and memory-efficient).

✅ Types:

Operator	Name	Example Result
&	AND	5 & 3 = 1
`	`	OR
^	XOR	5 ^ 3 = 6
~	NOT	~5 = -6
<<	Left shift	5 << 1 = 10
>>	Right shift	5 >> 1 = 2

📘 Example:

cCopyEditint a = 5, b = 3;
printf("AND: %d\n", a & b);
printf("OR: %d\n", a | b);

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5. 🧱 Linked Lists, Stacks, and Queues

✅ Linked List:

A list of dynamically connected nodes using pointers.

📘 Example: Singly Linked List

cCopyEditstruct Node {
    int data;
    struct Node *next;
};

✅ Stack (LIFO):

• Push, Pop
• Implement using arrays or linked lists

✅ Queue (FIFO):

• Enqueue, Dequeue
• Also using arrays or linked lists

📘 Stack with array:

cCopyEdit#define SIZE 5
int stack[SIZE], top = -1;
void push(int val) {
    if(top < SIZE - 1) stack[++top] = val;
}
int pop() {
    if(top >= 0) return stack[top--];
}

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6. 🧩 Complex Programs

📘 1. File-Based Student Record System

cCopyEdittypedef struct {
    int id;
    char name[30];
    float marks;
} Student;

void writeToFile() {
    FILE *fp = fopen("students.dat", "wb");
    Student s = {101, "Keshab", 93.5};
    fwrite(&s, sizeof(Student), 1, fp);
    fclose(fp);
}

void readFromFile() {
    FILE *fp = fopen("students.dat", "rb");
    Student s;
    fread(&s, sizeof(Student), 1, fp);
    printf("ID: %d, Name: %s, Marks: %.2f\n", s.id, s.name, s.marks);
    fclose(fp);
}

📘 2. Linked List-based Student Database

• Add, Delete, Search, Update student data
• Use malloc() to create nodes dynamically

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✅ Summary Table

Topic	Description	Example Function or Use
Dynamic Memory Allocation	Allocate/free memory at runtime	malloc(), free()
Advanced Pointers	Pointer to pointer, function pointers	void (*fp)()
File Handling	Read/write files	fopen(), fread()
Bitwise Operators	Bit manipulation	a & b, a << 1
Linked List / Stack/Queue	Data structures using pointers	struct Node
Complex Programs	File-based systems, DS implementation	Student DB System