Complete C Programming Tutorial for Beginners (2025)

1. Introduction to C

C is a general-purpose programming language developed in the early 1970s by Dennis Ritchie. It is known for its performance, portability, and close-to-hardware capabilities. It's widely used for operating systems, embedded systems, and as a foundation for other languages like C++, Java, and Python.

2. Structure of a C Program

A typical C program includes headers, the main function, and some statements. Let’s look at a basic structure:

#include <stdio.h>

int main() {
    printf("Hello, World!");
    return 0;
}
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Explanation:

• #include <stdio.h> includes the standard I/O library.
• main() is the entry point of every C program.
• printf() prints text to the screen.
• return 0; ends the program.

3. Variables and Data Types

Variables store data, and data types define what type of data you are working with:

int age = 25;
float height = 5.9;
char grade = 'A';
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Common Data Types:

• int – Integer numbers
• float – Decimal numbers
• char – Single characters
• double – Higher-precision float

4. Operators

Operators perform operations on variables and values:

• Arithmetic: +, -, *, /, %
• Relational: ==, !=, <, >, <=, >=
• Logical: &&, ||, !
• Assignment: =, +=, -=, *=, /=

5. Control Statements

Control statements help us control the flow of the program.

If-Else

int age = 18;
if (age >= 18) {
    printf("You are eligible to vote.");
} else {
    printf("You are not eligible to vote.");
}
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Switch

int day = 2;
switch (day) {
    case 1: printf("Monday"); break;
    case 2: printf("Tuesday"); break;
    default: printf("Other day");
}
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6. Loops

Loops repeat a block of code multiple times.

For Loop

for (int i = 0; i < 5; i++) {
    printf("%d\\n", i);
}
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While Loop

int i = 0;
while (i < 5) {
    printf("%d\\n", i);
    i++;
}
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7. Functions

Functions help organize code into reusable blocks.

int add(int a, int b) {
    return a + b;
}

int main() {
    int result = add(5, 3);
    printf("Sum is: %d", result);
    return 0;
}
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8. Arrays

Arrays store multiple values of the same data type.

int numbers[5] = {10, 20, 30, 40, 50};
printf("%d", numbers[2]); // Outputs 30
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9. Strings

Strings in C are arrays of characters.

char name[] = "Alice";
printf("Hello, %s!", name);
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10. Pointers

Pointers store memory addresses and allow powerful low-level access.

int x = 10;
int *p = &x;

printf("Value: %d\\n", *p);
printf("Address: %p", p);
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11. Structures

Structures group different types of data into a single unit.

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

struct Person p1 = {"John", 30};
printf("%s is %d years old.", p1.name, p1.age);
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12. File Handling

You can read/write files in C using file pointers.

FILE *fp = fopen("file.txt", "w");
fprintf(fp, "Hello, file!");
fclose(fp);
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13. Tips & Best Practices

• Use meaningful variable and function names.
• Always initialize variables before use.
• Comment your code for readability.
• Test and debug your code regularly.
• Use functions to avoid repetition.