trying to print the linkedlist for 2+ objects it prints infinite time

Code:

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#include<stdio.h>
#include<stdlib.h>
#include<String.h>
#include<ctype.h>
    /*car struct */
typedef struct car {
  unsigned int plate_number;
  unsigned int vin_number;
  char *Manufacturer_Name;
  char *model;
  char *colour;
  unsigned int year_Manufactured;
  unsigned int realseYear;
  unsigned int payment;
  unsigned int value;
  unsigned int engine_power;
  struct car *next;

} car;

car *cars;

/*function to scan and check the int input */
int CheckIntinput(unsigned int *a)
{

  char temp[20];
  int i;
  int flag = 1;
  while (1) {
    scanf("%s", temp);
    for (i = 0; i < strlen(temp); i++) {
      if (!isdigit(temp)) {
        flag = 0;
        printf
            ("You did not enter a number , Please enter an argument's number\n");
        break;
      }
    }
    if (flag) {
      break;
    }
    flag = 1;
  }

  *a = strtoul(temp, NULL, 10);
  return 1;
}

/*function to check if the information of the car are correct */
void checkifcarnputiscorrect(unsigned int *plate_number,
                            unsigned int *vin_number,
                            unsigned int *year_Manufactured,
                            unsigned int *realseYear, unsigned int *payment,
                            unsigned int *value, unsigned int *engine_power)
{
  int flag = 1;

  while (1) {
    printf("enter plate number :");
    CheckIntinput(plate_number);
    if (*plate_number > 9999999 || *plate_number < 1000000) {
      printf("plate number should be 7 digits try again \n");
      flag = 0;
    }
    /*
      if(!checkifcaralreadyinlist(*plate_number))
      {
      printf("the car is already in the list \n");
      flag=0;
      } */
    if (flag) {
      break;
    }
    flag = 1;
  }

  while (1) {
    printf("enter vin number :");
    CheckIntinput(vin_number);
    if (*vin_number > 99999 || *vin_number < 10000) {
      printf("vin_number should be 5 digits try again\n");
      flag = 0;
    }
    if (flag) {
      break;
    }
    flag = 1;
  }

  while (1) {
    printf("enter year manfucatured :");
    CheckIntinput(year_Manufactured);
    if (*year_Manufactured > 9999 || *year_Manufactured < 1000) {
      printf("yeaer_manfucatured should be 4 digits try again\n");
      flag = 0;
    }
    if (flag) {
      break;
    }
    flag = 1;
  }

  while (1) {
    printf("enter realese year :");
    CheckIntinput(realseYear);
    if (*realseYear > 9999 || *realseYear < 1000) {
      printf("realse year  should be 4 digits try again \n");
      flag = 0;
    }
    if (flag) {
      break;
    }
    flag = 1;
  }

  while (1) {
    printf("enter payment :");
    CheckIntinput(payment);
    if (*payment > 9999999 || *payment < 0) {
      printf("payment should be between 0-9999999 digits\n");
      flag = 0;
    }
    if (flag) {
      break;
    }
    flag = 1;
  }

  while (1) {
    printf("enter value :");
    CheckIntinput(value);
    if (*value > 9999999 || *value < 0) {
      printf("value should be between 0-9999999 digits\n");
      flag = 0;
    }
    if (flag) {
      break;
    }
    flag = 1;
  }

  while (1) {
    printf("enter engine_power :");
    CheckIntinput(engine_power);
    if (*engine_power > 9999 || *engine_power < 1000) {
      printf("engine power be 4 digits\n");
      flag = 0;
    }
    if (flag) {
      break;
    }
    flag = 1;
  }
}

/*function to scan and check if the input is only chars */
void Checkstringifonlychars(char *str)
{
  int i;
  int flag = 1;
  while (1) {
    scanf("%s", str);
    for (i = 0; i < strlen(str); i++) {
      if (!isalpha(str)) {
        flag = 0;
        printf("wrong input try input only chars.");
        break;
      }
    }
    if (flag) {
      break;
    }
    flag = 1;
  }


}

int CheckLonginput(unsigned long *a)
{

  char temp[20];
  int i;
  int flag = 1;
  while (1) {
    scanf("%s", temp);
    for (i = 0; i < strlen(temp); i++) {
      if (!isdigit(temp)) {
        flag = 0;
        printf
            ("You did not enter a number , Please enter an argument's number\n");
        break;
      }
    }
    if (flag) {
      break;
    }
    flag = 1;
  }

  *a = strtoul(temp, NULL, 10);
  return 1;
}

/*creating empty car list */

int createCarList()
{
  cars = (car *) malloc(sizeof(car));
  if (!cars) {
    return 0;
  }
  cars->next = NULL;
  return 1;
}

int addNewCar()
{
  unsigned int plate_number, vin_number, realseYear, year_Manufactured, payment,
      value, engine_power;
  char *Manufacturer_Name, *model, *colour, c;
  car *temp = NULL;
  car *p = NULL;
  temp = NULL;
  temp = (car *) malloc(sizeof(car));
  while (1) {
    checkifcarnputiscorrect(&plate_number, &vin_number, &year_Manufactured,
                            &realseYear, &payment, &value, &engine_power);

    Manufacturer_Name = (char *) malloc(10 * sizeof(char));
    printf("enter Manufacturer Name:");
    Checkstringifonlychars(Manufacturer_Name);

    model = (char *) malloc(10 * sizeof(char));
    printf("enter model:");
    Checkstringifonlychars(Model);

    colour = (char *) malloc(5 * sizeof(char));
    printf("enter colour of the car:");
    Checkstringifonlychars(colour);

    temp->plate_number = plate_number;
    temp->vin_number = vin_number;
    temp->Manufacturer_Name = Manufacturer_Name;
    temp->model = model;
    temp->colour = colour temp->year_Manufactured = year_Manufactured;
    temp->realseYear = realseYear;
    temp->payment = payment;
    temp->value = value;
    temp->engine_power = engine_power;
    temp->next = NULL;

    if (cars == NULL) {
      cars = temp;
    } else {
      p = cars;
      while (p->next != NULL) {
        p = p->next;
      }
      p->next = temp;
    }

    printf("\n done adding? if yes press y ");
    scanf(" %c", &c);
    if (c == 'y') {
      break;
    }


  }
  if (cars == NULL) {
    return 0;
  }
  return 1;
}

void printAllCars(void)
{

  car *tmp = cars;

  if (!cars) {
    printf("No Cars in list to Shown\n");
    return;
  }

  printf("\nCar List :\n\n");
  printf
      ("LicenseNum | chassisNum | makerName | modelName | color | productionYear | onRoadYear |  price  |  paidMoney  | engine");
  printf
      ("\n----------------------------------------------------------------------------------------------------------------------\n");
  while (tmp != NULL) {
    printf("%-11u ", tmp->plate_number);
    printf("%-13u ", tmp->vin_number);
    printf("%-11s ", tmp->Manufacturer_Name);
    printf("%-11s ", tmp->model);
    printf("%-7s ", tmp->colour);
    printf("%-16u ", tmp->year_Manufactured);
    printf("%-11u ", tmp->realseYear);
    printf("%-9u ", tmp->value);
    printf("%-14u ", tmp->payment);
    printf("%u\n", tmp->engine_power);
    tmp = tmp->next;
  }

  printf("\n");
}

int main()
{
  createCarList();
  addNewCar();
  printAllCars();
  return 0;
}

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