int disp_pin[7]; /* array for a-g pins of 7-Segment display */ 
void setup() 
{ 
    pinMode(6, OUTPUT); 
    pinMode(7, OUTPUT); 
    pinMode(8, OUTPUT); 
    pinMode(9, OUTPUT); 
    pinMode(10, OUTPUT); 
    pinMode(11, OUTPUT); 
    pinMode(12, OUTPUT); 
    int j=12;
    for(int k=0;k<=6;k++&j--)
    {
        disp_pin[k]=j;
    }
    //define_segment_pins(12,11,10,9,8,7,6); 
    /* a-g segment pins to Arduino */ 
} 
void loop() 
{ 
    int i; 
    for(i = 9; i>=0; i--) 
    { 
        display_number(i);
        delay(1000); 
    }
 
    for(i = 0; i<=9; i++) 
    { 
        display_number(i); 
        delay(1000); 
    }
}
// void define_segment_pins(int a, int b, int c, int d, int e, int f, int g)
//  /* Assigns 7-segment display pins to board */ 
// { 
//     disp_pin[0] = a; 
//     disp_pin[1] = b; 
//     disp_pin[2] = c; 
//     disp_pin[3] = d; 
//     disp_pin[4] = e; 
//     disp_pin[5] = f; 
//     disp_pin[6] = g; 
// } 
void display_number(int num) /* Function for displaying number (0-9) */ 
{ 
    switch(num) 
    { 
        case 0:
            digitalWrite(disp_pin[0], LOW); /* Drive disp_pin[0] to LOW */
            digitalWrite(disp_pin[1], LOW); /* Driving LOW turns on LED segment for common anode display */
            digitalWrite(disp_pin[2], LOW); 
            digitalWrite(disp_pin[3], LOW);
            digitalWrite(disp_pin[4], LOW); 
            digitalWrite(disp_pin[5], LOW); 
            digitalWrite(disp_pin[6], HIGH); 
            break; 
        case 1: 
            digitalWrite(disp_pin[0], HIGH); /* Drive disp_pin[7] to HIGH */
            digitalWrite(disp_pin[1], LOW);
            digitalWrite(disp_pin[2], LOW); 
            digitalWrite(disp_pin[3], HIGH); /* Driving HIGH turns off LED segment for common anode display */
            digitalWrite(disp_pin[4], HIGH); 
            digitalWrite(disp_pin[5], HIGH); 
            digitalWrite(disp_pin[6], HIGH); 
            break; 

        case 2: 
            digitalWrite(disp_pin[0], LOW);
            digitalWrite(disp_pin[1], LOW); 
            digitalWrite(disp_pin[2], HIGH); 
            digitalWrite(disp_pin[3], LOW); 
            digitalWrite(disp_pin[4], LOW); 
            digitalWrite(disp_pin[5], HIGH); 
            digitalWrite(disp_pin[6], LOW); 
            break; 
        case 3: 
            digitalWrite(disp_pin[0], LOW); 
            digitalWrite(disp_pin[1], LOW); 
            digitalWrite(disp_pin[2], LOW); 
            digitalWrite(disp_pin[3], LOW);
            digitalWrite(disp_pin[4], HIGH); 
            digitalWrite(disp_pin[5], HIGH); 
            digitalWrite(disp_pin[6], LOW);
            break; 
        case 4: 
            digitalWrite(disp_pin[0], HIGH); 
            digitalWrite(disp_pin[1], LOW); 
            digitalWrite(disp_pin[2], LOW); 
            digitalWrite(disp_pin[3], HIGH); 
            digitalWrite(disp_pin[4], HIGH); 
            digitalWrite(disp_pin[5], LOW); 
            digitalWrite(disp_pin[6], LOW); 
            break;
        case 5 :
            digitalWrite(disp_pin[0], LOW); 
            digitalWrite(disp_pin[1], HIGH); 
            digitalWrite(disp_pin[2], LOW); 
            digitalWrite(disp_pin[3], LOW); 
            digitalWrite(disp_pin[4], HIGH); 
            digitalWrite(disp_pin[5], LOW); 
            digitalWrite(disp_pin[6], LOW); 
        break; 
            case 6: 
            digitalWrite(disp_pin[0], LOW); 
            digitalWrite(disp_pin[1], HIGH); 
            digitalWrite(disp_pin[2], LOW); 
            digitalWrite(disp_pin[3], LOW); 
            digitalWrite(disp_pin[4], LOW); 
            digitalWrite(disp_pin[5], LOW);
            digitalWrite(disp_pin[6], LOW); 
            break; 
        case 7: 
            digitalWrite(disp_pin[0], LOW); 
            digitalWrite(disp_pin[1], LOW); 
            digitalWrite(disp_pin[2], LOW); 
            digitalWrite(disp_pin[3], HIGH); 
            digitalWrite(disp_pin[4], HIGH); 
            digitalWrite(disp_pin[5], HIGH); 
            digitalWrite(disp_pin[6], HIGH); 
            break; 
        case 8: 
            digitalWrite(disp_pin[0], LOW); 
            digitalWrite(disp_pin[1], LOW); 
            digitalWrite(disp_pin[2], LOW); 
            digitalWrite(disp_pin[3], LOW); 
            digitalWrite(disp_pin[4], LOW); 
            digitalWrite(disp_pin[5], LOW); 
            digitalWrite(disp_pin[6], LOW); 
            break; 
        case 9: 
            digitalWrite(disp_pin[0], LOW); 
            digitalWrite(disp_pin[1], LOW); 
            digitalWrite(disp_pin[2], LOW); 
            digitalWrite(disp_pin[3], LOW); 
            digitalWrite(disp_pin[4], HIGH); 
            digitalWrite(disp_pin[5], LOW);
            digitalWrite(disp_pin[6], LOW); 
            break; 
        default: 
            digitalWrite(disp_pin[0], HIGH); 
            digitalWrite(disp_pin[1], LOW); 
            digitalWrite(disp_pin[2], LOW); 
            digitalWrite(disp_pin[3], LOW); 
            digitalWrite(disp_pin[4], LOW); 
            digitalWrite(disp_pin[5], HIGH); 
            digitalWrite(disp_pin[6], LOW); 
            break; 
    }
}