Need help to output columns

**Kokoys** · 05-04-2015

Hey I have made a program that prints out 100 random numbers, but the numbers are printed in a long list. I want the output to be in 5 columns of 20 numbers each column, I've tried various ways and the output would always be an endless loop. ( I've used a for loop ) the code here is a full working code with the long list. Please help :/

Code:

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


int main(void){
	
  int counter,ascending,sort,search;
  int files[100];
   
 
  printf("Random file numbers\n");
 
	srand(time(NULL));
	for(counter=0;counter<100;counter++){
    files[counter] = rand()%9999+1;
	printf("%d\n", files[counter]);
  }

I think this part of the code is enough rather than the whole code which is too long.

**laserlight** · 05-04-2015

Try using nested for loops: the outer loop will loop 20 times; the inner loop will loop 5 times.

**Kokoys** · 05-04-2015

I know this will get me a facepalm or something but I'm really new to programming, I added this and I got an endless loop output

Code:

 for (counter1=0; counter1<5; counter1++){   
        for (counter=0; counter<20; counter++){
        
		printf ("%d", files[counter]);
		}
        printf ("\n");
    }
    
}

**hk_mp5kpdw** · 05-04-2015

As is often the case, the issue can be approached in many ways. One such alternate still using a single loop is: test the result of the value of the counter variable modulus 5 within the loop to decide when to print a newline instead of always printing a newline as you currently do.

**laserlight** · 05-04-2015

Originally Posted by Kokoys

I know this will get me a facepalm or something but I'm really new to programming, I added this and I got an endless loop output

With nested loops, each loop should have its own counter variable.

**Kokoys** · 05-04-2015

I don't know what the problem is, I'm always getting an endless loop, can you show me an example please ?

**laserlight** · 05-04-2015

Originally Posted by Kokoys

I don't know what the problem is, I'm always getting an endless loop, can you show me an example please ?

The problem is that because you reuse the variable named counter in both the inner and outer loops, you keep resetting counter to 0 when you should not do so. Consider this program that prints 4 columns of asterisks with 3 asterisks per column:

Code:

#include <stdio.h>

int main(void)
{
    int i;
    for (i = 0; i < 3; i++)
    {
        int j;
        for (j = 0; j < 4; j++)
        {
            printf("*");
        }
        printf("\n");
    }
    return 0;
}

**Kokoys** · 05-04-2015

I'm using counter and counter1

**laserlight** · 05-04-2015

Do you actually need the array? I assumed that you either would change your array to a 2D array, or get rid of it since you don't seem to need more than one variable.

If you prefer to keep the array and have it be a 1D array, then you can either compute the index, or you may find hk_mp5kpdw's suggestion to be simpler for such a case.

Originally Posted by Kokoys

I'm using counter and counter1

In that case your loop will not be an infinite loop.

**Kokoys** · 05-04-2015

I have to keep the array, that's the problem, It's part of a task I'm doing, I don't know how to do what hk_mp5kpdw told me to, ( I tried, but I failed )

**laserlight** · 05-04-2015

What is the code that you tried?

**Kokoys** · 05-04-2015

I tried something like this but still failing

Code:

srand(time(NULL));
	for(counter=0;counter<100;counter++){
    files[counter] = rand()%9999+1;
	for(counter1=0;counter1<5;counter++){
		for(a=1;a<20;a++){
			if(counter1 == 20){
				counter1 = 0;
					printf("\n");
				}
			}
		}
	


	printf("%d\n", files[counter]);
  }

**laserlight** · 05-04-2015

If you want to use hk_mp5kpdw's suggestion, then you will not have nested loops.

**Kokoys** · 05-04-2015

I'll just leave it as it is, I can't do it, I can't waste any more time on it I have loads off stuff to work on, thanks for helping.

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