The C language is known for its straightforward syntax and structure, which lays the foundation for many other programming languages. Here is an overview of the basic syntax in C:

1. Structure of a C Program

A typical C program has the following structure:

#include <stdio.h>  // Preprocessor directive

int main() {
    // Statements go here
    printf("Hello, World!\n");
    return 0;
}

• #include <stdio.h>: This is a preprocessor directive that includes the standard input/output library. It allows the program to use functions like printf().
• int main(): The main() function is the entry point of every C program. The execution starts from here.
• return 0;: Indicates that the program finished successfully. Non-zero values usually indicate an error.

2. Data Types

C supports several basic data types, which determine the type of data a variable can hold:

• Integer Types: int, short, long, unsigned int
• Floating-Point Types: float, double
• Character Type: char (used to store a single character)
• Void: void (used for functions that do not return a value)

Example:

int age = 25;
float height = 5.9;
char initial = 'A';

3. Variables

Variables are used to store data. They must be declared before they are used, specifying their type.

int number;        // Declaration
number = 10;       // Initialization

4. Constants

Constants are values that cannot be changed during the program execution. You can use #define or const.

• Using #define:

  #define PI 3.14
  

• Using const:

  const int MAX_AGE = 100;
  

5. Operators

C provides a range of operators:

• Arithmetic Operators: +, -, *, /, %
• Relational Operators: ==, !=, <, >, <=, >=
• Logical Operators: && (AND), || (OR), ! (NOT)
• Assignment Operators: =, +=, -=, *=, /=
• Increment/Decrement Operators: ++, --

Example:

int a = 5, b = 10;
int sum = a + b;  // sum is 15

6. Control Flow Statements

C provides several statements to control the flow of execution.

• Conditional Statements:

  • if, else if, else:

    if (a > b) {
        printf("a is greater than b");
    } else {
        printf("b is greater or equal to a");
    }
    

  • switch Statement: Used for multi-way branching.

    switch (choice) {
        case 1:
            printf("Choice is 1");
            break;
        case 2:
            printf("Choice is 2");
            break;
        default:
            printf("Invalid choice");
    }
    

• Loops:

  • for Loop:

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

  • while Loop:

    int count = 0;
    while (count < 5) {
        printf("%d ", count);
        count++;
    }
    

  • do...while Loop:

    int count = 0;
    do {
        printf("%d ", count);
        count++;
    } while (count < 5);
    

7. Functions

Functions allow you to modularize code by encapsulating specific tasks. A function has the following syntax:

return_type function_name(parameter_list) {
    // Function body
}

Example:

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

int main() {
    int result = add(5, 3);
    printf("Sum: %d\n", result);
    return 0;
}

8. Input/Output

C provides functions for input and output through the stdio.h library:

• printf(): Used to output text to the console.
• scanf(): Used to read input from the user.

Example:

int age;
printf("Enter your age: ");
scanf("%d", &age);
printf("You entered: %d\n", age);

9. Comments

Comments are used to explain code and are ignored by the compiler.

• Single-line comment: // This is a single-line comment
• Multi-line comment:

  /*
    This is a multi-line comment
  */
  

Summary

• Program Structure: Includes headers, the main() function, and statements.
• Data Types and Variables: Declaring and initializing data.
• Operators: Performing operations on data.
• Control Flow: Using if, switch, loops (for, while, do-while).
• Functions: Reusable blocks of code.
• Input/Output: Using printf() and scanf() to interact with the user.
• Comments: For readability.

These are the basic building blocks of C programming. Understanding them is crucial to writing functional and efficient C programs.