Difference between the outputs.

I am new to C programming. Please , tell me , why there is difference between the outputs of the two programs below.

Code:

---

#include<stdio.h>
int main()
{
  int i=0,j=0;




  for(;i<=20;i++)
    {
        for(;j<=10;j++)
            {
                    printf("%d\t%d\n",i,j);
            }


    }
    return 0;
  }

---

Code:

---

#include<stdio.h>
int main()
{
  int i,j;




  for(i=1;i<=20;i++)
    {
        for(j=1;j<=10;j++)
            {
                    printf("%d\t%d\n",i,j);
            }


    }
    return 0;
  }

---

Because i and j is initialized with different values.

Does this looks different?

Code 1:
i = 0
j = 0

Code 2:
i = 1
j = 1

That is ok

But the outer loop is not working in the first one . ,, In the second one the outer loop and inner loop is working.

Quote:

---

Originally Posted by psaikia

That is ok

But the outer loop is not working in the first one . ,, In the second one the outer loop and inner loop is working.

---

In the first example, What is the initial value of j when i > 0 ?

Quote:

---

Originally Posted by sparkomemphis

In the first example, What is the initial value of j when i > 0 ?

---

Did not understand , what are you trying to mean,plz elaborate.

This one got me too @@, The inner loop on the first code will only work once. j needs to be reinitialized to 1 or 0 on the inner loop so it will work properly.

Quote:

---

Originally Posted by mnd22

This one got me too @@, The inner loop on the first code will only work once. j needs to be reinitialized to 1 or 0 on the inner loop so it will work properly.

---

Yeah you are correct ,In the 1st code if we reinitialize the j in second loop , it works.

Can you explain me why it is like this ? thank you.

Quote:

---

Originally Posted by psaikia

Yeah you are correct ,In the 1st code if we reinitialize the j in second loop , it works.

Can you explain me why it is like this ? thank you.

---

What is the value of j after the first pass through the inner loop?

Since the first example (stupidly) removes the initializer from the for loops and places them outside both loops, the value of j will stay wherever the inner loop left it the first time through... Second time, j = 11... the loop does not run.

I've seen this broken format of for loops quite frequently over the past few weeks. Your code demonstrates perfectly why it's broken!

Your condition checks if j is <= 10. After the first loop j is 11 so without setting it to 0 again the result will always be false.

It's a pretty simple code you should try running it through your mind or if you have a good IDE try stepping through the code in debug mode.

Yeah , now I understand , Thank you ​commontater and mnd22