“ rand（）”不起作用，每次执行后我都会得到相同的数字

Question

So i am creating a ATM program for my programming class, long story short, i have to create about four random numbers. My issue is my program will not create different numbers, the numbers i get when i execute my program are the same over and over. I had srand(time(NULL)); in my main function and since my variables were global i tried to move it out of main next to my global variables, this left me with a un-compliable error. HELPPP!!!!

#include<stdio.h>
#include<time.h>
#include<stdlib.h>
#include<string.h>


int account_number = rand() % 5, pin = rand() % 3, chk_acc_bal = rand() % 4, sav_acc_bal = rand() % 5;

Answer 1

srand is a function call, this can't be placed in file scope, you can only place declarations, there.

Leave it in main , this is the place where it ought to be.

Answer 2

the problem here is that you are trying to initialize your vars at file scope with function calls.

Just try initializing your variables within your main function. Something like (I tested and works):

#include<stdio.h>
#include<time.h>
#include<stdlib.h>
#include<string.h>

int account_number, pin, chk_acc_bal, sav_acc_bal;

int main(void)
{
    srand(time(NULL));

    account_number = rand() % 5;
    pin = rand() % 3;
    chk_acc_bal = rand() % 4;
    sav_acc_bal = rand() % 5;

    printf("%d\n",account_number);
    printf("%d\n",pin);
    printf("%d\n",chk_acc_bal);
    printf("%d\n",sav_acc_bal);

    return 0;
}

Hope it helps. Best!

Answer 3

Call

srand(time(NULL));

once at the start of main . To initialize global variables with some random value using rand , use:

#include<stdio.h>
#include<time.h>
#include<stdlib.h>
#include<string.h>

int account_number, pin, chk_acc_bal, sav_acc_bal;

int main()
{
  srand(time(NULL)); //Call srand in the start of main

  account_number = rand() % 5; //Initialize variables with a random value from here
  pin = rand() % 3; 
  chk_acc_bal = rand() % 4; 
  sav_acc_bal = rand() % 5;

  //Rest of the code