C Program to Print Alphabet O Pattern

In this article, we will show how to write a C program to print the Alphabet O pattern or shape of stars using for loop, while loop, and functions.

#include <stdio.h>

int main() {
	int rows;

	printf("Enter Rows = ");
	scanf("%d", &rows);

	for (int i = 0; i < rows; i++)
	{
		for (int j = 0; j < rows; j++)
		{
			if(((i == 0 || i == rows - 1) && (0 < j < rows - 1)) || 
					((j == 0 || j == rows - 1) && (0 < i < rows - 1)))
			{
				printf("*");
			}
			else
			{
				printf(" ");
			}
		}
		printf("\n");
	}
	return 0;
}

Enter Rows = 15
*********
*             *
*             *
*             *
*             *
*             *
*             *
*             *
*             *
*             *
*             *
*             *
*             *
*             *
*********

Instead of a for loop, this Alphabet O Pattern of stars program uses a while loop to iterate the rows and columns. For more star programs, click here.

#include <stdio.h>

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

	printf("Enter Rows = ");
	scanf("%d", &rows);

	i = 0;
	while ( i < rows)
	{
		j = 0;
		while ( j < rows)
		{
			if((i == 0 || i == rows - 1) && (0 < j < rows - 1))
			{
				printf("*");
			}
			else if ((j == 0 || j == rows - 1) && (0 < i < rows - 1))
			{
				printf("*");
			}
			else
			{
				printf(" ");
			}
			j++;
		}
		printf("\n");
		i++;
	}
	return 0;
}

Enter Rows = 12
********
*          *
*          *
*          *
*          *
*          *
*          *
*          *
*          *
*          *
*          *
********

In this C program, we create an alphabetOPat function that accepts those values and prints the Alphabet O shape or pattern of the given char.

#include <stdio.h>

void alphabetOPat(int rows, char a)
{
	for (int i = 0; i < rows; i++)
	{
		for (int j = 0; j < rows; j++)
		{
			if(((i == 0 || i == rows - 1) && (0 < j < rows - 1)) ||
					((j == 0 || j == rows - 1) && (0 < i < rows - 1)))
			{
				printf("%c", a);
			}
			else
			{
				printf(" ");
			}
		}
		printf("\n");
	}
}

int main()
{
	int rows;
	char a;

	printf("Enter Alphabet =  ");
	scanf("%c", &a);

	printf("Enter Rows = ");
	scanf("%d", &rows);

	alphabetOPat(rows, a);
	return 0;
}