C Statements

1. What is a Statement?

• A computer program is a list of instructions for the computer to execute.
• In a programming language, these instructions are called statements.
• Each statement tells the computer to perform a specific action (like print, calculate, or stop).

2. Example Statement

printf(“Hello, World!”);

Explanation:

• This statement instructs the compiler to print “Hello, World!” on the screen.
• Every statement in C must end with a semicolon ( ; ) — this marks the end of the instruction.

3. Importance of Semicolon

• The semicolon ( ; ) is very important in C.
• If you forget to write ;, your program will show an error and won’t run.

Example:

printf(“Hello World!”)   // ❌ Missing semicolon

Error:

error: expected ‘;’ before ‘return’

4. Many Statements in a Program

• Most C programs contain many statements.
• The statements are executed one by one, in the same order as they are written.

Example:

printf(“Hello World!”);

printf(“Have a good day!”);

return 0;

5. Example Explained

➡️ The computer runs them top to bottom, one after another.

🗣️ Simple Summary

💬 A statement is a single instruction.
Every statement must end with a semicolon ( ; ).
The computer executes statements in order, one by one.

C Output (Print Text)

1. What is Output?

• In C programming, output means displaying text or values on the screen.
• To show output, we use the printf() function.

2. Syntax of printf()

printf(“text”);

• The text or message you want to display must be written inside double quotes (” “).
• Each printf statement ends with a semicolon ( ; ).

3. Example Program

#include <stdio.h>

int main() {

    printf(“Hello World!”);

    return 0;

}

Output:

Hello World!

🔹 4. Important Rule — Use Double Quotes

• Text (also called string) must be inside double quotes (” “).
• If you forget them, you will get an error.

✅ Correct:

printf(“This sentence will work!”);

❌ Wrong:

printf(This sentence will produce an error.);

Error Message:

error: expected expression before ‘This’

5. Using Many printf() Functions

You can use multiple printf() statements in one program.

Example:

#include <stdio.h>

int main() {

    printf(“Hello World!”);

    printf(“I am learning C.”);

    printf(“And it is awesome!”);

    return 0;

}

Output:

Hello World!I am learning C.And it is awesome!

6. Note

• By default, printf() does not add a new line between outputs.
• If you want to print on a new line, use \n (newline character).

Example with newline:

printf(“Hello World!\n”);

printf(“I am learning C.\n”);

Output:

Hello World!

I am learning C.

C Comments

1. What are Comments?

• Comments are used to explain code and make it more readable.
• They help programmers understand what the code does.
• The compiler ignores comments, meaning they do not get executed.
• Comments are also useful when testing or disabling code temporarily.

2. Types of Comments in C

There are two types of comments in C:

1. Single-line comments
2. Multi-line comments
3. Single-line Comments

• A single-line comment starts with //.
• Anything written after // on that line will be ignored by the compiler.

Example 1:

// This is a comment

printf(“Hello World!”);

Example 2:

printf(“Hello World!”); // This is a comment

💬 Single-line comments are mostly used for short notes or quick explanations.

4. Multi-line Comments

• A multi-line comment starts with /* and ends with */.
• Everything written between them will be ignored by the compiler.

Example:

/* The code below will print the words

   Hello World! to the screen */

printf(“Hello World!”);

💬 Multi-line comments are useful for long explanations or when you want to comment out multiple lines of code.

5. Choosing Between the Two

6. Historical Note 🕓

Before C99 version (1999), C supported only multi-line comments (/* … */).
From C99 onward, single-line comments (//) were added.

🗣️ Simple Summary

 Comments make code easier to read and understand.
 The compiler ignores all comments.
 Use // for short comments and /* … */ for long comments.