const int segmentA = 0;
const int segmentB = 1;
const int segmentC = 2;
const int segmentD = 3;
const int segmentE = 4;
const int segmentF = 5;
const int segmentG = 6;
const int segmentDP = 7; 
const byte ROWS = 4; 
const byte COLS = 4; 
char keys[ROWS][COLS] = 
{
  {'1', '2', '3', 'A'},
  {'4', '5', '6', 'B'},
  {'7', '8', '9', 'C'},
  {'*', '0', '#', 'D'}
};
byte rowPins[ROWS] = {16,17,18,19}; 
byte colPins[COLS] = {11,12,13,14};

void setup() 
{
    pinMode(segmentA, OUTPUT);
    pinMode(segmentB, OUTPUT);
    pinMode(segmentC, OUTPUT);
    pinMode(segmentD, OUTPUT);
    pinMode(segmentE, OUTPUT);
    pinMode(segmentF, OUTPUT);
    pinMode(segmentG, OUTPUT);
    pinMode(segmentDP, OUTPUT); 
    pinMode(rowPins[0], OUTPUT);
    pinMode(rowPins[1], OUTPUT);
    pinMode(rowPins[2], OUTPUT);
    pinMode(rowPins[3], OUTPUT);
    pinMode(colPins[0], INPUT_PULLUP);
    pinMode(colPins[1], INPUT_PULLUP);
    pinMode(colPins[2], INPUT_PULLUP);
    pinMode(colPins[3], INPUT_PULLUP);
}
void displayDigit(char digit) 
{
    digitalWrite(segmentA, LOW);
    digitalWrite(segmentB, LOW);
    digitalWrite(segmentC, LOW);
    digitalWrite(segmentD, LOW);
    digitalWrite(segmentE, LOW);
    digitalWrite(segmentF, LOW);
    digitalWrite(segmentG, LOW);
    digitalWrite(segmentDP, LOW); 
    switch (digit) 
    {
        case '0':
            digitalWrite(segmentA, HIGH);
            digitalWrite(segmentB, HIGH);
            digitalWrite(segmentC, HIGH);
            digitalWrite(segmentD, HIGH);
            digitalWrite(segmentE, HIGH);
            digitalWrite(segmentF, HIGH);
            break;
        case '1':
            digitalWrite(segmentB, HIGH);
            digitalWrite(segmentC, HIGH);
            break;
        case '2':
            digitalWrite(segmentA, HIGH);
            digitalWrite(segmentB, HIGH);
            digitalWrite(segmentD, HIGH);
            digitalWrite(segmentE, HIGH);
            digitalWrite(segmentG, HIGH);
            break;
        case '3':
            digitalWrite(segmentA, HIGH);
            digitalWrite(segmentB, HIGH);
            digitalWrite(segmentC, HIGH);
            digitalWrite(segmentD, HIGH);
            digitalWrite(segmentG, HIGH);
            break;
        case '4':
            digitalWrite(segmentB, HIGH);
            digitalWrite(segmentC, HIGH);
            digitalWrite(segmentF, HIGH);
            digitalWrite(segmentG, HIGH);
            break;
        case '5':
            digitalWrite(segmentA, HIGH);
            digitalWrite(segmentC, HIGH);
            digitalWrite(segmentD, HIGH);
            digitalWrite(segmentF, HIGH);
            digitalWrite(segmentG, HIGH);
            break;
        case '6':
            digitalWrite(segmentA, HIGH);
            digitalWrite(segmentC, HIGH);
            digitalWrite(segmentD, HIGH);
            digitalWrite(segmentE, HIGH);
            digitalWrite(segmentF, HIGH);
            digitalWrite(segmentG, HIGH);
            break;
        case '7':
            digitalWrite(segmentA, HIGH);
            digitalWrite(segmentB, HIGH);
            digitalWrite(segmentC, HIGH);
            break;
        case '8':
            digitalWrite(segmentA, HIGH);
            digitalWrite(segmentB, HIGH);
            digitalWrite(segmentC, HIGH);
            digitalWrite(segmentD, HIGH);
            digitalWrite(segmentE, HIGH);
            digitalWrite(segmentF, HIGH);
            digitalWrite(segmentG, HIGH);
            break;
        case '9':
            digitalWrite(segmentA, HIGH);
            digitalWrite(segmentB, HIGH);
            digitalWrite(segmentC, HIGH);
            digitalWrite(segmentD, HIGH);
            digitalWrite(segmentF, HIGH);
            digitalWrite(segmentG, HIGH);
            break;
        case 'A':
            digitalWrite(segmentE, HIGH);
            digitalWrite(segmentF, HIGH);
            digitalWrite(segmentG, HIGH);
            digitalWrite(segmentA, HIGH);
            digitalWrite(segmentB, HIGH);
            digitalWrite(segmentC, HIGH);
            break;
        case 'B':
            digitalWrite(segmentA, HIGH);
            digitalWrite(segmentB, HIGH);
            digitalWrite(segmentC, HIGH);
            digitalWrite(segmentD, HIGH);
            digitalWrite(segmentE, HIGH);
            digitalWrite(segmentF, HIGH);
            digitalWrite(segmentG, HIGH);
            break;
        case 'C':
            digitalWrite(segmentA, HIGH);
            digitalWrite(segmentF, HIGH);
            digitalWrite(segmentE, HIGH);
            digitalWrite(segmentD, HIGH);
            break;
        case 'D':
            digitalWrite(segmentA, HIGH);
            digitalWrite(segmentB, HIGH);
            digitalWrite(segmentC, HIGH);
            digitalWrite(segmentD, HIGH);
            digitalWrite(segmentE, HIGH);
            digitalWrite(segmentF, HIGH);
            break;
        default:
            break;
    }
}
void loop() {
    for (int row = 0; row < ROWS; row++) 
    {
        digitalWrite(rowPins[row], LOW);
        for (int col = 0; col < COLS; col++) {
            if (digitalRead(colPins[col]) == LOW) 
            {
                char key = keys[row][col];
                displayDigit(key);
                delay(200); 
                while (digitalRead(colPins[col]) == LOW);
            }
        }
        digitalWrite(rowPins[row], HIGH);
    }
    delay(1); 
}