---
title: 1.29 Basic C Program Structure
description: "A C program is organized into declarations, definitions, statements, and functions. The `main()` function serves as the entry point of a hosted C program. ``` #include int add(int a, int b) { return a + b; } int main() {…"
url: "https://edcret.in/docs/c-programming/basic-refreshers/1-29-basic-c-program-structure/"
updated: "2026-09-06"
category: C Programming / Basic Refreshers
---

# 1.29 Basic C Program Structure

A C program is organized into declarations, definitions, statements, and functions. The `main()` function serves as the entry point of a hosted C program.

```
#include <stdio.h>

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

int main()
{
    int result = add(10, 20);

    printf("%d\n", result);

    return 0;
}
```

### Example Output

```
30
```

### Explanation

The program contains several structural elements.

```
#include <stdio.h>
```

The preprocessor directive includes the standard I/O header so that `printf()` can be used.

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

This defines a function named `add`. It accepts two `int` parameters and returns an `int`.

```
int main()
```

defines the program's `main` function.

```
{
    int result = add(10, 20);

    printf("%d\n", result);

    return 0;
}
```

The braces define the body of `main`. The statements inside the body execute when `main` is called as the program's entry point.

### Basic C Program Elements

| Element | Example | Purpose |
| --- | --- | --- |
| Preprocessor directive | `#include <stdio.h>` | Processed before compilation |
| Function definition | `int add(...)` | Defines a function |
| Declaration | `int result;` | Declares an object |
| Initialization | `int result = 30;` | Gives an initial value |
| Expression statement | `result = 10;` | Evaluates an expression |
| Function call | `printf(...)` | Calls a function |
| Compound statement | `{ ... }` | Groups declarations and statements |
| Return statement | `return 0;` | Returns from a function |

A C source file can contain multiple functions, declarations, definitions, and preprocessor directives. The exact organization depends on the program, but execution in a hosted environment begins with `main()`.