Grade 10 COMPUTER SCIENCE

Programming in C Language

8.1 Introduction to Programming Languages

Q 8.1.1: What is a computer program?

Answer: A program is a set of instructions that tells the computer what to do step-by-step to solve a problem.

Q 8.1.2: Program syntax vs semantics?

Syntax: Rules of writing code (spelling, brackets, semicolons).
Semantics: Meaning of the code (what the code actually does).

Q 8.1.3: Levels of programming languages

Low level:

Machine language: 0s and 1s; hardware understands it directly.
Assembly language: Short codes like MOV, ADD; needs an assembler.

High level:

Procedural: Step-by-step procedures (C, Pascal).
Structured: Uses blocks, selection, loops (C).
Object-oriented: Uses objects/classes (C++, Java).

Q 8.1.4: Features of high-level languages

Easy to read/write, portable (runs on many machines with a compiler), faster development, fewer hardware details.

Q 8.1.5: Assembler vs Compiler vs Interpreter

Assembler: Converts assembly → machine code.
Compiler: Converts whole source code → machine code at once (e.g., C).
Interpreter: Runs code line-by-line (e.g., Python). Slower but easier to test.

8.2 Programming Environment Q 8.2.1: What is an IDE?

Answer: An IDE (Integrated Development Environment) is software that gives editor, compiler, debugger, and tools in one place.

Q 8.2.2: Common IDE menus (what they do)

File: New, Open, Save, Exit.
Edit: Cut, Copy, Paste, Undo/Redo.
Search: Find/Replace text.
Compile/Build: Turn code into an executable.
Debug: Run with breakpoints, watch variables.
Project: Manage multiple files.
Options/Settings: Change fonts, compiler settings.
Window: Arrange open files.
Help: Docs and shortcuts.

8.3 Programming Basics

Q 8.3.1: What are header files?

Answer: Files that contain declarations for functions you use. Example: stdio.h for printf/scanf.

Q 8.3.2: Structure of a C program

Preprocessor directives: #include, #define
main() function: starting point
Body: statements inside { }
Variables: global (outside functions) and local (inside a function/block)

Example:

#include <stdio.h> // preprocessor

#define PI 3.14 // macro

int main() { // main function

int r = 2; // local variable

float area = PI * r * r;

printf("Area = %.2f\n", area);

return 0;

}

Q 8.3.3: Purpose of comments

Explain code for humans; compiler ignores them.
Single-line: // this is a comment
Multi-line: /* comment */

8.4 Constants and Variables Q 8.4.1: Constant vs Variable

Variable: value can change (int age = 15;).
Constant: value cannot change (const float PI = 3.14;).

Q 8.4.2: Rules for variable names

Only letters, digits, underscore; cannot start with a digit; no spaces; no keywords; case-sensitive.

Q 8.4.3: Basic C data types (typical sizes on 32-bit/64-bit compilers; may vary)

int: 4 bytes
float: 4 bytes
char: 1 byte
long int: 4 or 8 bytes (often 8 on 64-bit) Note: Use sizeof(type) in your compiler to confirm.

Q 8.4.4: Declare and initialize variables and constants

#include <stdio.h>

int main() {

int count = 10; // variable

float price = 99.50;

char grade = 'A';

long int big = 100000L;

const float PI = 3.14159; // constant

printf("%d %.2f %c %ld %.2f\n", count, price, grade, big, PI);

return 0;

}

Q 8.4.5: Implicit vs explicit type casting

SLO 8.4.5 TYPECASTING

🟢 What is Typecasting in C?

Typecasting means changing the data type of a variable from one type to another.

For example:

Converting an int (integer) into a float (decimal number).
Converting a char into an int, etc.

🟡 Types of Typecasting

1. Implicit Typecasting (Type Conversion / Type Promotion)

Done automatically by the compiler.
Smaller data types are automatically converted into larger data types to avoid data loss.

Example:


int x = 10;
float y = x;   // int is automatically converted to float

Here, 10 becomes 10.0 automatically.

Prog:

#include<stdio.h>

#include<conio.h>

main()

{

int x = 10;

float y = x;

printf("%f",y);

}

2. Explicit Typecasting

Done manually by the programmer.
You write the type in front of the value/variable you want to convert.

Example:


float a = 10.5;
int b = (int)a;   // float is explicitly converted to int

Here, 10.5 becomes 10 (decimal part is removed).

#include<stdio.h>

#include<conio.h>

main()

{

float a = 10.5;

/*int b = (int)a;*/ // float is explicitly converted to int

printf("%f",a);

}

🔵 C Program for Both Implicit & Explicit Typecasting


#include <stdio.h>

int main() {
    // Implicit Typecasting Example
    int x = 10;
    float y;
    
    y = x; // int is automatically converted to float
    printf("Implicit Typecasting:\n");
    printf("Integer value: %d\n", x);
    printf("Converted to float (automatically): %.2f\n\n", y);

    // Explicit Typecasting Example
    float a = 9.78;
    int b;
    
    b = (int)a; // float is explicitly converted to int
    printf("Explicit Typecasting:\n");
    printf("Float value: %.2f\n", a);
    printf("Converted to int (manually): %d\n", b);

    return 0;
}

🟣 Output of the Program


Implicit Typecasting:
Integer value: 10
Converted to float (automatically): 10.00

Explicit Typecasting:
Float value: 9.78
Converted to int (manually): 9

✅ So the difference is:

Implicit → compiler does it automatically.
Explicit → programmer does it manually by writing (type) before the variable.

Section 9: Fundamentals of Input and Output

9.1 Input and Output Functions in C

Q 9.1.1: Output with putchar, puts, printf

In C programming, there are many ways to display text (output) on the screen. Three common ones are:

putchar() → prints one character at a time.
puts() → prints an entire string (sentence or word), and automatically goes to a new line.
printf() → the most powerful, can print characters, words, numbers, variables, and formatted output.

1. `putchar()`

👉 Think of putchar() as writing one letter at a time.
It can only display a single character.

Example:


#include <stdio.h>

int main() {
    putchar('A');   // prints A
    putchar('\n');  // prints a newline (go to next line)
    putchar('B');   // prints B
    return 0;
}

Output:

A
B

📌 Notice: 'A' and 'B' are in single quotes because they are characters.

2. `puts()`

👉 Think of puts() as writing a whole word or sentence.
It prints the string and automatically moves to the next line.

Example:


#include <stdio.h>

int main() {
    puts("Hello World");
    puts("C Programming is fun!");
    return 0;
}

Output:


Hello World
C Programming is fun!

📌 puts() always ends with a newline — you don’t need to write \n.

3. `printf()`

👉 printf() is the most flexible.
It can print:

Characters
Strings (sentences)
Numbers (integers, decimals)
Even mix them together with formatting

Example:


#include <stdio.h>

int main() {
    printf("Hello, World!\n");   // simple text
    printf("I am %d years old.\n", 20); // prints number (integer)
    printf("The price is %.2f dollars\n", 99.50); // prints decimal with 2 places
    printf("First letter is %c\n", 'A'); // prints a character
    return 0;
}

Output:


Hello, World!
I am 20 years old.
The price is 99.50 dollars
First letter is A

📌 Here %d, %f, %c are format specifiers (placeholders) for numbers, decimals, and characters.

✅ Summary for Layman:

putchar() → like pressing one key on the keyboard.
puts() → like typing a whole sentence and then pressing Enter.
printf() → like typing anything you want (letters, numbers, mix) with full control.

Q 9.1.2: Format specifiers examples

#include <stdio.h>

int main() {

// a. Decimal (using integer with %d)

int decimalNumber = 25;

printf("Decimal (integer value): %d\n", decimalNumber);

// b. Integer (same as decimal in C, %d)

int integerNumber = -42;

printf("Integer: %d\n", integerNumber);

// c. Float (decimal notation) -> %f

float pi = 3.14159;

printf("Float (decimal notation): %f\n", pi);

// d. Float (exponential / scientific notation) -> %e or %E

float bigNumber = 12345.6789;

printf("Float (exponential notation): %e\n", bigNumber);

// e. Character -> %c

char letter = 'A';

printf("Character: %c\n", letter);

// f. Long integer -> %ld

long int bigInteger = 1234567890;

printf("Long integer: %ld\n", bigInteger);

// g. String (sequence of characters) -> %s

char name[] = "Hello, World!";

printf("String: %s\n", name);

return 0;

}

OUTPUT

Decimal number: 25

Integer number: -42

Float (decimal notation): 3.141590

Float (exponential notation): 1.234568e+04

Character: A

Long integer: 1234567890

String: Hello, World!

Step 2: Break down 25

The digits are: 2 and 5
Positions:
- 2 is in the tens place → multiply by $10^1 = 10$
- 5 is in the ones place → multiply by $10^0 = 1$

Step 3: Calculate

25_{(10)} = (2 \times 10^1) + (5 \times 10^0)

= (2 \times 10) + (5 \times 1)

= 20 + 5

= 25

Q 9.1.3: Input with scanf, getch, getche, getchar, gets

🧠 Concept Before Code:

Function	Description
`scanf()`	Takes formatted input (like numbers or words).
`getch()`	Takes a single character input without showing it on the screen.
`getche()`	Takes a single character input and shows it on the screen.
`getchar()`	Reads a single character (shows it like getche).
`gets()`	Takes a line of text as input (stops at Enter). (unsafe, but good for basic learning)

💻 C Program:


#include <stdio.h>
#include <conio.h>  // for getch() and getche()

int main() {
    int age;
    char grade;
    char name[50];
    char ch;

    // Using scanf()
    printf("Enter your age: ");
    scanf("%d", &age);

    // Clear input buffer before using gets()
    fflush(stdin);

    // Using gets()
    printf("Enter your full name: ");
    gets(name);

    // Using getchar()
    printf("Enter your grade (A, B, C...): ");
    grade = getchar();

    // Using getch()
    printf("\nPress any key (it will NOT be shown): ");
    ch = getch();
    printf("\nYou pressed: %c\n", ch);

    // Using getche()
    printf("Press any key again (it WILL be shown): ");
    ch = getche();
    printf("\nYou pressed: %c\n", ch);

    // Output summary
    printf("\n\n--- Your Details ---\n");
    printf("Name: %s\n", name);
    printf("Age: %d\n", age);
    printf("Grade: %c\n", grade);

    return 0;
}

🧾 Sample Output:


Enter your age: 16
Enter your full name: Ali Khan
Enter your grade (A, B, C...): A
Press any key (it will NOT be shown): 
You pressed: X
Press any key again (it WILL be shown): Y
You pressed: Y

--- Your Details ---
Name: Ali Khan
Age: 16
Grade: A

🧠 Simple Explanation (For Class or Notes)

🟢 1. `scanf()`

Use: To take formatted input from the user — like numbers, characters, or words.
Example:


int age;
scanf("%d", &age);

➡️ It reads an integer value and stores it in the variable age.

Explain Like This:

"scanf() is used when we want to take input in a specific format, for example an integer or a float.
It stops reading when you press SPACE or ENTER."

🟢 2. `getch()`

Use: To take one character input without showing it on the screen.
Example:


char ch;
ch = getch();

➡️ If you type A, nothing will appear — but the program will store 'A' in ch.

Explain Like This:

"getch() is used when we want to take a single key input secretly — for example, in password fields or “Press any key to continue” screens."

🟢 3. `getche()`

Use: To take one character input and show it on the screen.
Example:


char ch;
ch = getche();

➡️ If you type A, it will appear on the screen and be stored in ch.

Explain Like This:

"getche() is like getch() but it displays the key you press."

🟢 4. `getchar()`

Use: Reads one character from the keyboard (and shows it).
Example:


char grade;
grade = getchar();

➡️ If you type A and press Enter, it will store 'A' in grade.

Explain Like This:

"getchar() takes only one character as input — for example, your grade A, B, or C."

🟢 5. `gets()`

Use: Reads a whole line of text including spaces.
Example:


char name[50];
gets(name);

➡️ If you type Ali Khan, the full name is stored in the name variable.

Explain Like This:

"gets() is used to take string input (like your name or sentence).
Unlike scanf("%s", ...), it can read spaces too."

🧾 Summary Table for Notes

Function	Input Type	Shows Input?	Example Use	Remarks
`scanf()`	Words, numbers	✅ Yes	Taking age, marks, etc.	Stops at space or Enter
`getch()`	Single character	❌ No	Hidden key input	Used in “Press any key”
`getche()`	Single character	✅ Yes	Character input	Shows what you press
`getchar()`	Single character	✅ Yes	Input like grade	Waits for Enter
`gets()`	String (text line)	✅ Yes	Full name or sentence	Reads spaces too

Q 9.1.4: What is an escape sequence?

A special backslash code that represents a non-printing character.

Q 9.1.5: Common escape sequences

\a alert (beep), \b backspace, \n newline, \r carriage return, \t tab, \ backslash, ' single quote, " double quote, ? question mark.

#include <stdio.h>

int main() {

printf("Hello\tWorld\nLine2\rCR test\n");

printf("Quotes: \' \" Backslash: \\\n");

return 0;

}

9.2 Operators in C Q 9.2.1: Arithmetic operators

#include <stdio.h>

int main(){

int a=9,b=4;

printf("+ %d\n", a+b);

printf("- %d\n", a-b);

printf("* %d\n", a*b);

printf("/ %d\n", a/b); // integer division → 2

printf("%% %d\n", a%b); // remainder → 1

return 0;

}

Q 9.2.2: Convert arithmetic expression to C

Example: Expression 3x^2 + 2x + 1 with x=2

int x=2; int y = 3*x*x + 2*x + 1;

Q 9.2.3: Solve an arithmetic problem

float price=99.5, qty=3;

float bill = price*qty;

Q 9.2.4: Assignment and compound assignment

int x=10;

x = x + 5; // same as:

x += 5; // other: -=, *=, /=, %=

📝 Assignment Operator (Layman Explanation)

👉 Imagine you have a box with a name written on it.
That box is called a variable (like x, y, marks, etc.).

The assignment operator (=) is like putting something inside the box.

Example 1: Simple Assignment


x = 10;

💡 Meaning: Put the number 10 inside the box named x.

Example 2: Updating the Value


x = x + 5;

💡 Meaning: Look inside the box x, take what is there, add 5 to it, and put the new value back in the same box.

If x was 10 before → now it becomes 15.

Shortcuts (Compound Assignment Operators)

These are just short ways to update the value in the box:

x += 5; → means x = x + 5;
x -= 3; → means x = x - 3;
x *= 2; → means x = x * 2;
x /= 4; → means x = x / 4;

Real Life Example 🎒

Think of your pocket money:

Start: money = 100; → you have 100 rupees.
money += 50; → you got 50 more → now 150.
money -= 30; → you spent 30 → now 120.
money *= 2; → your money doubled → now 240.

The = operator is simply saying: “Put this new value in the box again.”

✅ Program 1: Addition using `+=`


#include <stdio.h>
int main() {
    int x;
    printf("Enter a number: ");
    scanf("%d", &x);

    x += 5; // same as x = x + 5
    printf("After adding 5, value of x = %d\n", x);

    return 0;
}

✅ Program 2: Subtraction using `-=`


#include <stdio.h>
int main() {
    int x;
    printf("Enter a number: ");
    scanf("%d", &x);

    x -= 3; // same as x = x - 3
    printf("After subtracting 3, value of x = %d\n", x);

    return 0;
}

✅ Program 3: Multiplication using `*=`


#include <stdio.h>
int main() {
    int x;
    printf("Enter a number: ");
    scanf("%d", &x);

    x *= 2; // same as x = x * 2
    printf("After multiplying by 2, value of x = %d\n", x);

    return 0;
}

✅ Program 4: Division using `/=`


#include <stdio.h>
int main() {
    int x;
    printf("Enter a number: ");
    scanf("%d", &x);

    x /= 4; // same as x = x / 4
    printf("After dividing by 4, value of x = %d\n", x);

    return 0;
}

✅ Program 5: Combo Example (+=, -=, *=, /=)


#include <stdio.h>
int main() {
    int x;
    printf("Enter a number: ");
    scanf("%d", &x);

    x += 10; // add 10
    printf("After adding 10: %d\n", x);

    x -= 5; // subtract 5
    printf("After subtracting 5: %d\n", x);

    x *= 2; // multiply by 2
    printf("After multiplying by 2: %d\n", x);

    x /= 3; // divide by 3
    printf("After dividing by 3: %d\n", x);

    return 0;
}

🖥️ int main() and return 0; in C – Simple Explanation
1. int main()
Every C program starts running from a function called main().
The word int means that this function will return an integer (a number) back to the computer when it finishes.
Think of it like a promise:

👉 “Hey computer, when I finish running the program, I’ll give you a number as a report card.”

2. return 0;
At the end of the program we usually write:
return 0;
Here, 0 means ‘everything went fine’.
If the program gives some other number, it usually means there was a problem.
👉 In real life:

Imagine you submit your homework.
If the teacher writes 0 mistakes → everything is correct ✅.
If the teacher writes 5 mistakes → something went wrong ❌.
Same way, return 0; tells the computer:

👉 “I finished my work successfully without errors.”

3. Why do we need it in school programs?
In simple programs, even if you don’t write return 0;, many compilers still work fine.
But good practice is to always write it, because it makes the program complete and professional.

✅ So, in layman terms:
int main() → starting point of the program that promises to return a number when finished.
return 0; → that number, usually 0, which means “Program ran successfully.”

Q 9.2.5: Increment and decrement

📘 C Program: Using Increment and Decrement Operators


#include <stdio.h>

int main() {
    int a = 5, b = 10;

    // Display initial values
    printf("Initial values:\n");
    printf("a = %d, b = %d\n\n", a, b);

    // Using increment operator
    printf("Using increment operator:\n");
    printf("a++ = %d\n", a++); // Post-increment: use value first, then increment
    printf("Now a = %d\n", a);
    printf("++b = %d\n", ++b); // Pre-increment: increment first, then use value
    printf("Now b = %d\n\n", b);

    // Using decrement operator
    printf("Using decrement operator:\n");
    printf("a-- = %d\n", a--); // Post-decrement: use value first, then decrement
    printf("Now a = %d\n", a);
    printf("--b = %d\n", --b); // Pre-decrement: decrement first, then use value
    printf("Now b = %d\n", b);

    return 0;
}

🧠 Explanation

a++ → Post-increment → use the value of a first, then increase it by 1
++b → Pre-increment → increase the value of b first, then use it
a-- → Post-decrement → use the value of a first, then decrease it by 1
--b → Pre-decrement → decrease the value of b first, then use it

🧾 Example Output


Initial values:
a = 5, b = 10

Using increment operator:
a++ = 5
Now a = 6
++b = 11
Now b = 11

Using decrement operator:
a-- = 6
Now a = 5
--b = 10
Now b = 10

RELATIONAL OPERATOR

🔹 List of Relational Operators in C
Operator Meaning Example Result
== Equal to 5 == 5 True (1)
!= Not equal to 5 != 3 True (1)
> Greater than 7 > 4 True (1)
< Less than 3 < 8 True (1)
>= Greater than or equal to 6 >= 6 True (1)
<= Less than or equal to 2 <= 5 True (1)

🔹 Example Program
#include <stdio.h>

int main() {
    int a = 10, b = 20;

    printf("a == b: %d\n", a == b);
    printf("a != b: %d\n", a != b);
    printf("a > b : %d\n", a > b);
    printf("a < b : %d\n", a < b);
    printf("a >= b: %d\n", a >= b);
    printf("a <= b: %d\n", a <= b);

    return 0;
}

🔹 Output:
a == b: 0
a != b: 1
a > b : 0
a < b : 1
a >= b: 0
a <= b: 1

Operator	Meaning	Example	Result
`==`	Equal to	`5 == 5`	True (1)
`!=`	Not equal to	`5 != 3`	True (1)
`>`	Greater than	`7 > 4`	True (1)
`<`	Less than	`3 < 8`	True (1)
`>=`	Greater than or equal to	`6 >= 6`	True (1)
`<=`	Less than or equal to	`2 <= 5`	True (1)

Q 9.2.6: Relational operators

<, >, <=, >=, == (equal), != (not equal). They return 1 (true) or 0 (false).

int a=5, b=7;

printf("%d\n", a < b); // 1

Q 9.2.7: Logical operators

&& AND, || OR, ! NOT

int age=20; int hasID=1;

if (age>=18 && hasID) printf("Allowed\n");

SLO NO.9.2.7
Use the following logical operators in a C program
AND(&&)
OR(||)
NOT(!)

Q. Write a Program to check if number is divisible by 2 or not.

Solution:

Q 9.2.8: Difference between = and ==

= assigns a value: x = 5;
== compares values: if (x == 5) …

Q 9.2.9: Unary vs Binary operators

Unary: works on one value (++, --, !, unary -).
Binary: works on two values (+, -, *, /, %, <, >, &&, ||).

Q 9.2.10: Conditional (ternary) operator

int a=10, b=20;

int max = (a>b) ? a : b; // if a>b then a else b

TERNARY

Q 9.2.11: Operator precedence (simple idea)

Highest: (), unary +/-, ++/--, !
Then: *, /, %
Then: +, -
Then: <, <=, >, >=
Then: ==, !=
Then: &&
Then: ||
Lowest: =, +=, -= … Tip: Use parentheses to make your intention clear.

Section 10: Control Structures

Q 10.1.1: What is a control statement?

Answer: A statement that controls the flow of a program (decision-making or selection and repetition). Examples: if, if-else, switch.

Q 10.1.2: What is a conditional statement?

Answer: A statement that runs code only if a condition is true. Examples: if, if-else, if-else-if, switch.

Q 10.1.3: Structure of if

if (condition) {

// statements when condition is true

}

Q 10.1.4: Program using if

Copy code

int marks=75;

if (marks >= 50) printf("Pass\n");

Q 10.1.5: Structure of if-else

Copy code

if (condition) {

// true part

} else {

// false part

}

Q 10.1.6: Program using if-else

int num=7;

if (num%2==0) printf("Even\n");

else printf("Odd\n");

Q 10.1.7: Structure of if-else-if

if (cond1) { ... }

else if (cond2) { ... }

else { ... }

Q 10.1.8: Program using if-else-if (grading)

int m=83;

if (m>=85) printf("A");

else if (m>=70) printf("B");

else if (m>=50) printf("C");

else printf("Fail");

Q 10.1.9: Structure of switch

switch (expression) {

case value1: /* statements */ break;

case value2: /* statements */ break;

default: /* statements */

}

Q 10.1.10: Advantages and disadvantages of switch

Advantages: Clean and readable for many fixed choices, faster than many if-else in some cases.
Disadvantages: Works only with integral types (int/char, not ranges), no relational conditions like > or <, must remember break to avoid fall-through.

Q 10.1.11: Program using switch

‘Schar op = '+';

int a=7,b=3;

switch(op){

case '+': printf("%d\n", a+b); break;

case '-': printf("%d\n", a-b); break;

case '*': printf("%d\n", a*b); break;

case '/': printf("%d\n", b!=0 ? a/b : 0); break;

default: printf("Unknown\n");

}

___________________________________________________________________________________________________

SWITCH NESTED

___________________________________________________________________________________

IF AND ELSE

ELSE IF

SWITCH

___________________________________________________________________________________

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Tuesday, December 9, 2025

Thursday, December 4, 2025

SLO 8.1.1 TILL SLO 10.1.11 WITH SOLUTION

🟢 What is Typecasting in C?

🟡 Types of Typecasting

1. Implicit Typecasting (Type Conversion / Type Promotion)

2. Explicit Typecasting

🔵 C Program for Both Implicit & Explicit Typecasting

🟣 Output of the Program

1. putchar()

Example:

2. puts()

Example:

3. printf()

Example:

Step 2: Break down 25

Step 3: Calculate

💻 C Program:

🧾 Sample Output:

🧠 Simple Explanation (For Class or Notes)

🟢 1. scanf()

🟢 2. getch()

🟢 3. getche()

🟢 4. getchar()

🟢 5. gets()

🧾 Summary Table for Notes

📝 Assignment Operator (Layman Explanation)

Example 1: Simple Assignment

Example 2: Updating the Value

Shortcuts (Compound Assignment Operators)

Real Life Example 🎒

✅ Program 1: Addition using +=

✅ Program 2: Subtraction using -=

✅ Program 3: Multiplication using *=

✅ Program 4: Division using /=

✅ Program 5: Combo Example (+=, -=, *=, /=)

🖥️ int main() and return 0; in C – Simple Explanation

1. int main()

2. return 0;

3. Why do we need it in school programs?

📘 C Program: Using Increment and Decrement Operators

🧠 Explanation

🧾 Example Output

🔹 List of Relational Operators in C

🔹 Example Program

🔹 Output:

1. `putchar()`

2. `puts()`

3. `printf()`

🟢 1. `scanf()`

🟢 2. `getch()`

🟢 3. `getche()`

🟢 4. `getchar()`

🟢 5. `gets()`

✅ Program 1: Addition using `+=`

✅ Program 2: Subtraction using `-=`

✅ Program 3: Multiplication using `*=`

✅ Program 4: Division using `/=`

🖥️ `int main()` and `return 0;` in C – Simple Explanation

1. `int main()`

2. `return 0;`