C Programming – Day 4 | Loops in C (for, while, do-while) Explained for Beginners

LOOP IN C (for, while, do-while)

DAY - 4

let’s begin 🚀

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📍 Day-4 — Loops in C (for, while, do-while)

Loops repeat a block of code many times ✅

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✅ 1️⃣ for Loop

Used when number of repetitions is known

for(int i = 1; i <= 5; i++) {
    printf("%d\n", i);
}

Output:

1
2
3
4
5

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✅ 2️⃣ while Loop

Used when number of repetitions is unknown

int i = 1;
while(i <= 5){
    printf("%d\n", i);
    i++;
}

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✅ 3️⃣ do-while Loop

Executes block at least once

int i = 1;
do {
    printf("%d\n", i);
    i++;
} while(i <= 5);

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✅ Difference Summary

Feature	for	while	do-while
Initialization in loop	Yes	No	No
Condition check first	✅ Yes	✅ Yes	❌ Executes once first
Guaranteed at least once?	❌ No	❌ No	✅ Yes

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🧮 Example: Multiplication Table

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

for(int i=1; i<=10; i++){
    printf("%d x %d = %d\n", n, i, n*i);
}

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✅ Task-4

Write a program to:

✔ Input a number
✔ Using while loop
✔ Print sum of digits

Example:

Input: 456
Output: 15

(Because 4+5+6 = 15)

📌 Hint:

• %10 → last digit

• /10 → remove last digit

✅ Send me your code — I will fix if needed

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📝 Quick Quiz — Day-4

Reply like: 1C, 2A, 3B

1️⃣ Which loop runs at least once always?
A) for
B) while
C) do-while

2️⃣ Repeat 1 to 10 → which loop is best?
A) for
B) while
C) switch

3️⃣ %10 gives:
A) Division
B) Last digit
C) Whole number

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✅ Your turn now!

Send:
👉 Task-4 code
👉 Day-4 quiz answers

✅ NEXT - DAY - 5