Hi ,need help

I have a homework I designed 0-99 counters but our teacher tried a lot of things that I wanted to increase it with a button but I could not code the button I could help you find the wrong place

const int a=2;
const int b=3;
const int c=4;
const int d=5;
const int e=6;
const int f=7;
const int g=8;
const int dp=9;
const int konlar=10;
const int kbirler=11;
const int but=12;
int sayici;

void setup() {
(butondurumu)=digitalRead(but);
if (butondurumu==0)
{sayici=sayici+1;}

for(int i=2;i<12;i++)
{delay(100);
pinMode(i,OUTPUT);
}
pinMode(but,INPUT_PULLUP);
sayici=0;
}

void loop() {
int birler=sayici%10;
int onlar=sayici/10;
int i=0;
while(i<35)
{
goster(birler);
digitalWrite(kbirler,HIGH);
digitalWrite(konlar,LOW);
//delay(10);
goster(onlar);
digitalWrite(kbirler,LOW);
digitalWrite(konlar,HIGH);
//delay(10);
//i++;
}
//sayici++;

if (sayici==100)
sayici=0;

}
void goster(int n)
{
switch(n)
{
case 0:
digitalWrite(a,HIGH);
digitalWrite(b,HIGH);
digitalWrite(c,HIGH);
digitalWrite(d,HIGH);
digitalWrite(e,HIGH);
digitalWrite(f,HIGH);
digitalWrite(g,LOW);
break;
case 1:
digitalWrite(a,LOW);
digitalWrite(b,HIGH);
digitalWrite(c,HIGH);
digitalWrite(d,LOW);
digitalWrite(e,LOW);
digitalWrite(f,LOW);
digitalWrite(g,LOW);
break;
case 2:
digitalWrite(a,HIGH);
digitalWrite(b,HIGH);
digitalWrite(c,LOW);
digitalWrite(d,HIGH);
digitalWrite(e,HIGH);
digitalWrite(f,LOW);
digitalWrite(g,HIGH);
break;
case 3:
digitalWrite(a,HIGH);
digitalWrite(b,HIGH);
digitalWrite(c,HIGH);
digitalWrite(d,HIGH);
digitalWrite(e,LOW);
digitalWrite(f,LOW);
digitalWrite(g,HIGH);
break;
case 4:
digitalWrite(a,LOW);
digitalWrite(b,HIGH);
digitalWrite(c,HIGH);
digitalWrite(d,LOW);
digitalWrite(e,LOW);
digitalWrite(f,HIGH);
digitalWrite(g,HIGH);
break;
case 5:
digitalWrite(a,HIGH);
digitalWrite(b,LOW);
digitalWrite(c,HIGH);
digitalWrite(d,HIGH);
digitalWrite(e,LOW);
digitalWrite(f,HIGH);
digitalWrite(g,HIGH);
break;
case 6:
digitalWrite(a,HIGH);
digitalWrite(b,LOW);
digitalWrite(c,HIGH);
digitalWrite(d,HIGH);
digitalWrite(e,HIGH);
digitalWrite(f,HIGH);
digitalWrite(g,HIGH);
break;
case 7:
digitalWrite(a,HIGH);
digitalWrite(b,HIGH);
digitalWrite(c,HIGH);
digitalWrite(d,LOW);
digitalWrite(e,LOW);
digitalWrite(f,LOW);
digitalWrite(g,LOW);
break;
case 8:
digitalWrite(a,HIGH);
digitalWrite(b,HIGH);
digitalWrite(c,HIGH);
digitalWrite(d,HIGH);
digitalWrite(e,HIGH);
digitalWrite(f,HIGH);
digitalWrite(g,HIGH);
break;
case 9:
digitalWrite(a,HIGH);
digitalWrite(b,HIGH);
digitalWrite(c,HIGH);
digitalWrite(d,HIGH);
digitalWrite(e,LOW);
digitalWrite(f,HIGH);
digitalWrite(g,HIGH);
break;
}

}

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void setup() {
  (butondurumu) = digitalRead(but);
  if (butondurumu == 0)
  {
    sayici = sayici + 1;
  }

  for (int i = 2; i < 12; i++)
  { delay(100);
    pinMode(i, OUTPUT);
  }
  pinMode(but, INPUT_PULLUP);
  sayici = 0;
}

You need to set the pinMode of the button before doing the digitalRead.

You need to understand that setup() only runs once when you first start the program running. So if you want the code to react to button presses after that time you will need to move your code that reads the button to loop().

You may want to learn about debouncing your button input. See File > Examples > 02.Digital > Debounce and https://www.arduino.cc/en/Tutorial/Debounce.

I thank you for the information you provided I am new to these topics I see the course for about 1 month I would like to thank you again

Why do you start a new post??