How does this code exactly work in C Language? (A Beginner Question)

Question

This code is for printing the inverse half pyramid:

* * * 
* * 
*

---

#include<stdio.h>
int main() {
    int i, j, rows;
    printf("Enter number of rows: ");
    scanf("%d", &rows);
    for (i=rows; i>=1; --i) 
    {
        for (j=1; j<=i; ++j)
        { 
            printf("* ");
        }
        printf("\n");
    }   
    return 0;
} 

Let's say if I enter rows = 5, then "i" will initialize its value as 5, check if it's greater than 1, then we go to the 2nd for loop, where j has the initial value of 1, and then check if it's less than the value of "i= 5", which it IS, then after that, how will the second loop run?

Answer 1

The first for loop is to decrement from 5 ( rows variable) to 1 (since it is inverted half pyramid).

The second/inner for loop (loop j ) is to print the * character i times ( i is set in outer for loop).

Once the inner for loop exits, a new line is printed ( \\n ) and i is decremented and the inner loop runs again for the new value of i .

Answer 2

* * * *
* * *
* *
*

The above pattern contains N rows and each row contains Ni + 1 columns (where i is the current row number). Considering this let us write a step by step descriptive logic to print inverted right triangle star pattern.

1. Input number of rows to print from user. Store it in a variable say rows .

2. To iterate through rows run an outer loop from 1 to rows . The loop structure should look like for(i=1; i<=rows; i++) .

3. To iterate through columns run an inner loop from i to rows . The loop structure should look like for(j=i; j<=rows; j++) . Inside this loop print star.

   Note: Instead of iterating from i to rows you can also iterate from 1 to rows - i + 1 .

4. After printing all columns of a row, move to next line ie print new line.

Good explanation taken from https://codeforwin.org/2015/07/inverted-right-triangle-star-pattern-program-in-c.html

/**
 * Reverse right triangle star pattern program in C
 */

#include <stdio.h>

int main()
{
    int i, j, rows;

    /* Input number of rows from user */
    printf("Enter number of rows : ");
    scanf("%d", &rows);

    /* Iterate through rows */
    for(i=1; i<=rows; i++)
    {
        /* Iterate through columns */
        for(j=i; j<=rows; j++)
        {
            printf("* ");
        }

        /* Move to the next line */
        printf("\n");
    }

    return 0;
}