Project on @yt.yeasin50

Calculator

Sat, 25 Oct 2025 20:00:00 +0600

A beginner-friendly C project where you’ll learn to build a Calculator using switch and functions.

Covers input handling, operator-based execution, and error fixing - everything explained clearly in Bangla.

First example code

without while

#include <stdio.h>

/// Function prototypes
float add(float a, float b);
float subtract(float a, float b);
float multiply(float a, float b);
float divide(float a, float b);

int main() {

 float a, b, result;
 char op;

 printf("Enter a:");
 scanf("%f",&a);

 printf("Enter b:");
 scanf("%f",&b);

 printf("Choose operation(+, -, *, /):");
 scanf(" %c", &op);


 switch (op) {
 case '+':
 result = add(a, b);
 break;

 case '-':
 result = subtract(a,b);
 break;

 case '*':
 result = multiply(a,b);
 break;

 case '/':
 result = divide(a,b);
 break;
 }

 printf("%.2f %c %.2f = %.2f\n", a, op, b, result);

 return 0;

}

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

float subtract(float a, float b){
 return a - b;
}

float multiply(float a, float b){
 return a * b;
}

float divide(float a, float b){
 return a /b;
}

Validate number(float)

 if(scanf("%f",&a) != 1){
 printf("Invalid input\n");
 return 0;
 }

validate operator

 if (op != '+' && op != '-' && op != '*' && op != '/'){
 printf("Invalid operation\n");
 return 0;
 }

Final code

#include <stdio.h>

// Function prototypes
float add(float a, float b);
float subtract(float a, float b);
float multiply(float a, float b);
float divide(float a, float b);

int main() {
 float num1, num2, result;
 char op;

 while (1) {
 // Input numbers
 printf("Enter first number: ");
 scanf("%f", &num1);
 printf("Enter second number: ");
 scanf("%f", &num2);

 // Display menu
 printf("\nChoose operation (+, -, *, /, = to exit): ");
 scanf(" %c", &op); // space before %c to skip whitespace

 if (op == 'q') {
 printf("Exiting program.\n");
 break;
 }

 switch (op) {
 case '+':
 result = add(num1, num2);
 printf("Result: %.2f\n", result);
 break;
 case '-':
 result = subtract(num1, num2);
 printf("Result: %.2f\n", result);
 break;
 case '*':
 result = multiply(num1, num2);
 printf("Result: %.2f\n", result);
 break;
 case '/':
 if (num2 != 0) {
 result = divide(num1, num2);
 printf("Result: %.2f\n", result);
 } else {
 printf("Error: Division by zero!\n");
 }
 break;
 default:
 printf("Invalid operation! Try again.\n");
 }

 printf("\n"); // Extra line before next iteration
 }

 return 0;
}

// Function definitions
float add(float a, float b) { return a + b; }
float subtract(float a, float b) { return a - b; }
float multiply(float a, float b) { return a * b; }
float divide(float a, float b) { return a / b; }

Number Guessing Game in C

Sun, 26 Oct 2025 20:00:00 +0600

How random works?

#include <stdlib.h>
int r = rand();

Generates a pseudo-random number between 0 and RAND_MAX.
Without seeding, the sequence is the same every run.

🌱 Seeding with `srand()`

#include <time.h>
srand(time(0));

srand() sets the starting point (seed) for rand().
time(0) and time(NULL) both give current time in seconds since 1970.
Using time as a seed ensures different sequences each run. “By using the current time as a seed, we make the numbers look random every time the program runs.”

Random Numbers in a Range

To generate a number between min and max:

CGPA & Grade Calculator in C

Mon, 27 Oct 2025 20:00:00 +0600

Learn how to build a CGPA & Grade Calculator in C step-by-step.

Final code

#include<stdio.h>

// mark between 0 -100
float cgpa(float mark){
 if(mark>100 || mark < 0) return 0;

 else if(mark >= 80) return 4.0;
 else if(mark >= 75) return 3.75;
 else if(mark >= 70) return 3.50;
 else if(mark >= 65) return 3.25;
 else if(mark >= 60) return 3.00;
 else if(mark >= 55) return 2.75;
 else if(mark >= 50) return 2.50;
 else if(mark >= 45) return 2.25;
 else if(mark >= 40) return 2.00;
 else return 0.0;
}

// CGPA to grade, where [cgpa] is between 0 - 4.0
char* cgpaToGrade(float cgpa) {
 if (cgpa > 4.0 || cgpa < 0) return "F";

 else if(cgpa >= 4.0) return "A+";
 else if(cgpa >= 3.75) return "A";
 else if(cgpa >= 3.5) return "A-";
 else if(cgpa >= 3.25) return "B+";
 else if(cgpa >= 3.0) return "B";
 else if(cgpa >= 2.75) return "B-";
 else if(cgpa >= 2.5) return "C+";
 else if(cgpa >= 2.25) return "C";
 else if(cgpa >= 2.0) return "D";
 else return "F";
}

/// [avg] is the mark between 0 - 100
char* calculateGrade(float avg){
 if (avg>100) return "invalid number";
 else if(avg >= 80) return "A+";
 else if(avg >= 75) return "A";
 else if(avg >= 70) return "A-";
 else if(avg >= 65) return "B+";
 else if(avg >= 60) return "B";
 else if(avg >= 55) return "B-";
 else if(avg >= 50) return "C+";
 else if(avg >= 45) return "C";
 else if(avg >= 40) return "D";
 else return "F";
}

int main(){

 int n, total=0;
 float cgpaTotal=0.0;

 printf("How many subject you like to calculate: ");
 scanf("%d", &n);

 for(int i=0; i< n; i++){
 int number ;
 printf("Enter your %d subject Mark: ", i +1);
 scanf("%d", &number);
 cgpaTotal += cgpa(number);
 total += number;
 }

 float avg = total/n;
 float result = cgpaTotal / n;
 char* grade = cgpaToGrade(result);

 printf("total number %d, average %.2f\n", total, avg);
 printf("Your CGPA %.2f %s\n", result, grade);
 return 0;
}

Quiz Game in C (File-Based)

Tue, 28 Oct 2025 20:00:00 +0600

Build a Quiz Game in C that reads questions from a file!
We also learn from hardcoded questions first before moving to file-based input.

What You’ll Learn:

Reading questions and answers from a file
Using arrays and strings to manage data
Implementing scoring logic

txt file data

Our quiz.txt file contains questions in the following format:

Student Mark Record Project in C

Wed, 29 Oct 2025 20:00:00 +0600

Build a Student Mark Record Project in C where you can create, show, and remove student records.
Learn how to manage data using structs, handle file input/output, and format outputs neatly.

Why `scanf(" %[^\n]", s.name);`?

%[^\n] → reads all characters until a newline, including spaces (so you can type full names like “Alice Bob”).

BMI calculator

Wed, 29 Oct 2025 20:00:00 +0600

We convert feet & inches to meters, calculate BMI, and show BMI category/status step by step — perfect for beginners learning C programming.

Final code

#include <stdio.h>

/// convert feet and inch to meter
float convertFeetInchToMeter(int feet, int inch) {
 return (feet * .3048) + (inch * .0254);
}

/// calculate BMI from [weight] in kg and [height] in meter
float bmi(float weight, float height) { return weight / (height * height); }

/// show message according to [bmi] which is a float
void showBMIMessage(float bmi) {
 if (bmi < 18.5) {
 printf("status: Underweight\n");
 } else if (bmi < 24.9) {
 printf("status: Normal\n");
 } else if (bmi < 29.9) {
 printf("status: Overweight\n");
 } else {
 printf("status: Obesity\n");
 }
}

int main() {
 float inch, feet, weight;

 printf("\nEnter your weight(kg): ");
 if (scanf("%f", &weight) != 1) {
 printf("invalid user input, please provide number\n");
 return 0;
 }

 printf("Enter your height(feet inch): ");
 if (scanf("%f %f", &feet, &inch) != 1) {
 printf("invalid user input, please provide number\n");
 return 0;
 }

 float height = convertFeetInchToMeter(feet, inch);
 float myBMI = bmi(weight, height);
 showBMIMessage(myBMI);
}

Temperature Converter

Fri, 21 Nov 2025 20:00:00 +0600

How to build a Temperature Converter in C that can convert between Celsius, Fahrenheit, and Kelvin. This beginner-friendly Bangla tutorial explains the logic step by step and includes full coding examples.

Final code

#include <stdio.h>

// show welcome message to choose conversion option
void welcome(){
 printf("Select conversion:\n");
 printf("1. Celsius to Fahrenheit\n");
 printf("2. Fahrenheit to Celsius\n");
 printf("3. Celsius to Kelvin\n");
 printf("4. Kelvin to Celsius\n");
}

int main(){
 int selectedOption;
 float temp;
 welcome();
 printf("Enter your choice:");
 scanf("%d", &selectedOption);

 printf("Enter temperature:");
 scanf("%f", &temp);

 switch (selectedOption) {
 case 1:
 printf("Farenheight: %.2f\n", (temp * 9/5) + 32);
 break;
 case 2:
 printf("Celsius: %.2f\n", (temp -32) * 5/9);
 break;
 case 3:
 printf("Kelvin: %.2f\n", temp+ 273.15);
 break;
 case 4:
 if(temp < 0){
 printf("Kelvin can not be smaller than 0\n");
 }else {
 printf("Kelvin: %.2f\n", temp - 273.15);
 }
 break;
 default:
 printf("Invalid choice\n");
 }
}

Currency Converter

Sun, 23 Nov 2025 20:00:00 +0600

Build a Currency Converter in C that can convert between USD, BDT, Gold value, and more! This Bangla tutorial explains the logic step-by-step, shows the full code, and includes a recap to help beginners understand everything clearly.

Final code

#include <stdio.h>

/// show gold price on each currency
void calculateGoldPrice(float gram) {
 double rateBDT = 16028.0;
 double rateUSD = 131.19;
 double rateEUR = 113.05;

 printf("Gold Price for %.5f gram\n", gram);
 printf("BDT: %.2f\n", gram * rateBDT);
 printf("USD: %.2f\n", gram * rateUSD);
 printf("EUR: %.2f\n", gram * rateEUR);
}


int main(){

 int choice;
 printf("Select conversion:\n");
 printf("1. USD to BDT\n");
 printf("2. BDT to USD\n");
 printf("3. USD to EUR\n");
 printf("4. Gold Price\n");
 printf("Enter choice: ");
 scanf("%d", &choice);

 float amount;
 printf("Enter amount:");
 scanf("%f", &amount);

 if(amount < 0){
 printf("Invalid amount\n");
 return 0;
 }
 printf("\n");
 switch (choice) {
 case 1:
 printf("BDT %.2f\n", amount * 120);
 break;
 case 2:
 printf("USD %.2f\n", amount / 120);
 break;
 case 3:
 printf("EUR %.2f\n", amount * .92);
 break;
 case 4:
 calculateGoldPrice(amount);
 break;
 default:
 printf("Invalid input\n");
 }
 return 0;
}

Electricity Calculator

Tue, 25 Nov 2025 20:00:00 +0600

How to build a complete Electricity Bill Calculator in C, using a tier-based billing system. In this Bangla tutorial, you’ll understand the logic behind electricity units, slabs, and how to calculate the final bill. Perfect for beginners working on C programming projects!

Final code

#include <stdio.h>

/// calculate bill for a single [tier]
float calculateTierBill(float unit, int tierLimit, int rate){
 int billedUnit = unit<tierLimit ? unit: tierLimit;
 return billedUnit * rate;
}

int main(){
 /// bill tiers
 int tierLimits[] = {50, 75, 100, 200};
 int rates[] = {5, 7, 9, 10};
 int totalTiers = sizeof(rates) / sizeof(rates[0]);

 float totalUnits;
 printf("Enter total used unit: ");
 if(scanf("%f", &totalUnits)!=1 || totalUnits <0){
 printf("Invalid input\n");
 return 0;
 }

 /// total bill
 float billed = 0;
 float remainingUnits = totalUnits;
 int i=0;

 while(remainingUnits >0){

 float tierBill;
 if(i< totalTiers){

 tierBill = calculateTierBill(remainingUnits, tierLimits[i], rates[i]);
 float billedUnit = remainingUnits < tierLimits[i]? remainingUnits: tierLimits[i];
 remainingUnits -= billedUnit;

 }else {
 tierBill = remainingUnits * rates[totalTiers-1];
 remainingUnits =0 ;
 }

 billed += tierBill;
 i++;
 }

 printf("Billed amount %.2f tk\n", billed);
 return 0;
}

Project on @yt.yeasin50

Calculator

First example code

Validate number(float)

validate operator

Final code

Number Guessing Game in C

How random works?

🌱 Seeding with srand()

Random Numbers in a Range

CGPA & Grade Calculator in C

Final code

Quiz Game in C (File-Based)

txt file data

Student Mark Record Project in C

Why scanf(" %[^\n]", s.name);?

BMI calculator

Final code

Temperature Converter

Final code

Currency Converter

Final code

Electricity Calculator

Final code

🌱 Seeding with `srand()`

Why `scanf(" %[^\n]", s.name);`?