C Pattern Program: Hourglass Star Shape

January 03, 2026

C Program to Check Prime Number Using Efficient Logic

Introduction A prime number is a number that has exactly two distinct positive divisors: 1 and itself. In this program, we check whether a given number is prime or not using a simple and efficient logic. This type of program is commonly used in mathematics, competitive programming, and basic algorithm learning for beginners in C programming. Problem Statement The task is to write a C program that determines whether a given integer is a prime number or not. The program takes a single integer input from the user and analyzes its divisibility. If the number has no divisors other than 1 and itself, it should be identified as a prime number; otherwise, it is not prime. This problem is important in number theory and has practical relevance in areas such as cryptography, data validation, and algorithm design. Algorithm / Logic Explanation To check whether a number is prime, we need to verify that it is not divisible by any number other than 1 and itself. The algorithm follows a si...

🔷 C Pattern Program: Hourglass Star Shape

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

📘 Explanation:

This C program prints a vertical hourglass-like star pattern using spaces and a single * per row.

🔹 The first loop prints the upper half: decreasing spaces followed by a star.
🔹 The second loop prints the lower half: increasing spaces followed by a star.
🔹 Together, it creates a symmetrical hourglass shape centered around the vertical axis.

🔍 Sample Output:

Enter the number: 5
    *
   *
  *
 *
*
 *
  *
   *
    *

🏷️ Keywords:

C pattern printing, star pattern, diamond pattern, vertical hourglass, single star pattern, C loop pattern examples

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C Program to Check Prime Number Using Efficient Logic