C program to print hollow square or rectangle star pattern

Write a C program to print hollow square or rectangle star(*) pattern series using for loop. How to print hollow square or rectangle star pattern of N rows using for loop in C programming. Logic to print empty square or rectangle star pattern in C program.

Enter number of rows: 5

*****
*   *
*   *
*   *
*****

Required knowledge

Basic C programming, If else, For loop, Nested loop

Logic to print hollow square star pattern

*****
*   *
*   *
*   *
*****

The above pattern is similar to square star pattern of N rows and N columns. Here star is printed only for first and last column or for first and last row.

Step by step descriptive logic to print empty square star pattern.

1. Input number of rows to print from user. Store it in a variable say N.
2. To iterate through rows, run an outer loop from 1 to N. For that define loop with structure for(i=1; i<=N; i++).
3. To iterate through columns, run an inner loop from 1 to N. Define loop with structure for(j=1; j<=N; j++).
4. Inside inner loop print star for first and last row or for first and last column. Which is print star if i==1 or i==N or j==1 or j==N, otherwise print space.
5. After printing all columns of a row, move to next line i.e. print a blank line after inner loop.

Program to print hollow square pattern

/**
 * C program to print hollow square star pattern
 */

#include <stdio.h>

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

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

    /* Iterate over each row */
    for(i=1; i<=N; i++)
    {
        /* Iterate over each column */
        for(j=1; j<=N; j++)
        {
            if(i==1 || i==N || j==1 || j==N)
            {
                /* Print star for 1st, Nth row and column */
                printf("*");
            }
            else
            {
                printf(" ");
            }
        }

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

    return 0;
}

Enter number of rows: 5 
*****
*   *
*   *
*   *
*****

Logic to print hollow rectangle star pattern

***************
*             *
*             *
*             *
***************

Logic to print hollow rectangle star pattern is similar to hollow square star pattern. The only difference is hollow square pattern is a NxN matrix whereas hollow rectangle pattern is a MxN matrix.

Step by step descriptive logic to print hollow rectangle star pattern.

1. Input number of rows and columns from user. Store it in a variable say rows and columns.
2. To iterate through rows, run an outer loop from 1 to rows. Define a loop with structure for(i=1; i<=rows; i++).
3. To iterate through columns, run an inner loop from 1 to columns. Define loop with structure for(j=1; j<=columns; j++).
4. Inside this loop print star for first or last row or for first or last column, otherwise print blank space. Which is if(i==1 || i==rows || j==1 || j==columns) then print star otherwise space.
5. After printing all columns of a row, move to next line i.e. print new line after inner loop.

Program to print hollow rectangle star pattern

/**
 * C program to print hollow rectangle star pattern
 */

#include <stdio.h>

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

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

    /* Iterate over each row */
    for(i=1; i<=rows; i++)
    {
        /* Iterate over each column */
        for(j=1; j<=columns; j++)
        {
            if(i==1 || i==rows || j==1 || j==columns)
            {
                /* Print star for 1st and last row, column */
                printf("*");
            }
            else
            {
                printf(" ");
            }
        }

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

    return 0;
}

Enter number of rows: 5 
Enter number of columns: 10
**********
*        *
*        *
*        *
**********

Happy coding