C Programming

• Write a program in C to print rectangular star (*) pattern of n rows and m columns using for loop.
• Write a C program to print a rectangle pattern of star (*) character using loops.

For a rectangular star pattern of 5 rows and 9 columns. Program’s output should be:

Required Knowledge

• For Loop
• printf and scanf function in C

Here is the matrix representation of the rectangle star pattern. The row numbers are represented by i whereas column numbers are represented by j.

C program to print rectangular star pattern

#include<stdio.h>
 
int main(){
    int rows, cols , i, j;
     
    printf("Enter rows and columns of rectangle\n");
    scanf("%d %d", &rows, &cols);
     
    /* Row iterator for loop */
    for(i = 0; i < rows; i++){
     /* Column iterator for loop */
        for(j = 0; j < cols; j++){
           printf("*");
        }
        printf("\n");
    }
    return 0;
}

Output

Enter rows and columns of rectangle
3 9
*********
*********
*********

• Write a program in C to print inverted right triangle star (*) pattern of n rows using for loop.
• Write a C program to print a inverted right angles triangle pattern of star (*) character using loops.

For a inverted right triangle star pattern of 7 rows. Program’s output should be:

Required Knowledge

• For Loop
• printf and scanf function in C

Algorithm to print inverted right triangle star pattern using loop

If you look closely, this pattern is the vertically inverted pattern of right triangle star pattern. As the row number increases from top to bottom, number of stars in a row decreases.
NOTE: The index of rows and columns starts from 0.

• Take the number of rows(N) of inverted right triangle as input from user using scanf function.
• Number of stars in K^th row is equal to (N – K + 1). In the pattern given above, N = 7. Hence, 1^st row contains 7 star, 2^nd row contains 6 stars, 3^rd row contains 5 stars.
• We will use two for loops to print inverted right triangle star pattern.
  • For a inverted right triangle star pattern of N rows, outer for loop will iterate N time(from i = 0 to N-1). Each iteration of outer loop will print one row of the pattern.
  • For j^th row of inverted right triangle pattern, inner loop will iterate N-j times(from j = 0 to N-j). Each iteration of inner loop will print one star character.

Here is the matrix representation of the inverted right triangle star pattern. The row numbers are represented by i whereas column numbers are represented by j.

C program to print inverted right triangle star pattern

#include<stdio.h>
 
int main() {
    int i,j,rows;
    printf("Enter the number of rows\n");
    scanf("%d", &rows);
 
    for(i = 0; i < rows; i++) {
        /* Prints one row of triangle */
        for(j = 0; j < rows - i; j++) {
            printf("* ");
        }
        /* move to next row */
        printf("\n");
    }
    return 0;
}

Output

Enter the number of rows
7
* * * * * * * 
* * * * * * 
* * * * * 
* * * * 
* * * 
* * 
*

• Write a program in C to print mirrored right angled triangle star (*) pattern using for loop.
• Write a C program to print a mirrored right angles triangle pattern of star (*) character of n rows.

For a mirrored right triangle star pattern of 7 rows. Program’s output should be:

Required Knowledge

• For Loop
• printf and scanf function in C

Algorithm to print mirrired right triangle star pattern using loop

C program to print mirrored right triangle star pattern is similar to the right triangle star pattern program. Once you understand how to print right triangle pattern then printing it’s mirrored pattern will be an easy task.

• Take the number of rows(N) of mirrored right triangle as input from user using scanf function.
• In any row, the sum of spaces and stars are equal to N. Number of stars increases by one and number of spaces before stars decreases by 1 in consecutive rows.
• In any row R, we will first print N-R-1 space characters then R+1 star characters.

Here is the matrix representation of the inverted triangle star pattern. The row numbers are represented by i whereas column numbers are represented by j.

C program to print mirrored right triangle star pattern

#include <stdio.h>
 
int main() {
    int i, j, rows;
 
    printf("Enter the number of rows\n");
    scanf("%d", &rows);
 
    for(i = 0; i < rows; i++){
        /* for j th row, first print rows-r spaces then stars */
        for(j = 0; j < rows; j++){
            if(j < rows-i-1){
                printf(" ");
            } else {
                printf("*");
            }
        }
        /* move to next row */
        printf("\n");
    }
    return 0;
}

Output

Enter the number of rows
6
     *
    **
   ***
  ****
 *****
******

Here is the C program to print inverted right triangle star pattern using one for loop

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

Output

Enter the number of rows
5
    *
   **
  ***
 ****
*****

• Write a program in C to print reversed inverted right triangle star (*) pattern of n rows using for loop.

For a reversed mirrored right triangle star pattern of 7 rows. Program’s output should be:

Required Knowledge

• For Loop
• printf and scanf function in C

Algorithm to print reversed mirrored right triangle star pattern using loop
If you look closely, this pattern is similar to inverted right triangle star pattern. For R^th row, we have to print R space characters before stars.

• Take the number of rows(N) of reversed inverted right triangle as input from user using scanf function.
• Each row(R) contains N characters, R space characters followed by N-R star (*) character.
• We will use two for loops. Outer for loop will print one row in one iteration.
• One iteration of inner loop will first print R space characters followed by N-R star (*) character

Here is the matrix representation of the mirrored triangle star pattern. The row numbers are represented by i whereas column numbers are represented by j.

C program to print reversed mirrired right triangle star pattern

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

Output

Enter the number of rows
6
******
 *****
  ****
   ***
    **
     *

• Write a program in C to print pyramid star pattern using for loop.
• Write a C program to print an equilateral triangle star pattern of n rows using loops.

For an equilateral triangle pyramid star pattern of 5 rows. Program’s output should be:

Required Knowledge

• For Loop
• printf and scanf function in C

Algorithm to print pyramid star pattern using loop
In this program, we are printing a pyramid star pattern in which i^th row contains (2*i + 1) space separated stars. The index of rows and columns starts from 0.

• We first take the number of rows(R) in the pattern as input from user using scanf function.
• One iteration of outer for loop will print a row of pyramid(from i = 0 to R – 1).
• For j^th row of pyramid, the inner for loop first prints (R – i – 1) spaces for every line and then nested while loop prints (2*j + 1) stars.

Here is the matrix representation of the pyramid star pattern. The row numbers are represented by i whereas column numbers are represented by j.

C program to print pyramid star pattern

#include<stdio.h>
 
int main() {
    int i, j, rows, star = 0;
    printf("Enter the number of rows\n");
    scanf("%d", &rows);
 
    /* printing one row in every iteration */
    for (i = 0; i < rows; i++) {
        /* Printing spaces */
        for (j = 0; j <= (rows - i - 1); j++) {
            printf(" ");
        }
        /* Printing stars */
        while (star != (2 * i + 1)) {
            printf("*");
            star++;;
        }
        star = 0;
        /* move to next row */
        printf("\n");
    }
    return 0;
}

Output

Enter the number of rows
6
     *
    ***
   *****
  *******
 *********
***********

• Write a C program to print rhombus star pattern using for loop.

For a rhombus star pattern of 6 rows. Program’s output should be:

Required Knowledge

• For Loop
• printf and scanf function in C

Algorithm to print rhombus star pattern using loop

• We first take the number of rows(N) as input from user using scanf function.
• The index of rows and columns will start from 0.
• Each row of rhombus star pattern contains N star characters.
• Each iteration of outer for loop(from i = 0 to N-1) will print one row of pattern at a time.
• Each j^th row, contains j space characters followed by N star characters.
• First inner for loop prints space characters whereas second inner for loop prints star characters.

Here is the matrix representation of the rhombus star pattern. The row numbers are represented by i whereas column numbers are represented by j.

 program to print rhombus star pattern

#include <stdio.h>
 
int main() {
    int i, j, rows;
 
    printf("Enter the number of rows\n");
    scanf("%d", &rows);
 
    for (i = 0; i < rows; i++) {
        /* Print spaces before stars in a row */
        for (j = 0; j < i; j++) {
            printf(" ");
        }
        /* Print rows stars after spaces in a row */
        for (j = 0; j < rows; j++) {
            printf("*");
        }
        /* jump to next row */
        printf("\n");
    }
    return 0;
}

Output

Enter the number of rows
6
******
 ******
  ******
   ******
    ******
     ******

A pointer to a pointer in C programming is a pointer variable which is used to store the address of another variable. A pointer can store the address of another pointer variable also like any other data type pointer.

A pointer to a pointer means, first pointer will contains the address of second pointer and second pointer can will contain the add of actual value stored in memory.

We use double * operator to define a pointer to a pointer.

<data_type> **<identifier>;

For Example

int count = 10;
int *ptr = &count; /* Pointer to an integer variable */
int **ptrToPtr = &ptr; /* Pointer to a pointer */ 

To access the value of count variable using pointer variable ‘ptr’, we need one asterisk operator(*) like

*ptr;

and to access the value of count variable using pointer to a pointer variable ‘ptrToPtr’, we need two asterisk operator(*) like

**ptrToPtr;

first asterisk returns the memory address stored inside pointer ‘ptr’ and second asterisk retrieves the value stored at memory location pointer by ‘ptr’.

C program to show the use of pointer to a pointer

#include <stdio.h>
#include <conio.h>
 
int main () {
   int count = 10;
   /* pointer to an integer variable */
   int *ptr = &count;
   /* pointer to a pointer*/
   int **ptrToPtr = &ptr;
    
   printf("Value of count variable = %d\n", count);
   printf("Value of count variable retreived uisng ptr %d\n", *ptr);
   printf("Value of count variable retreived uisng ptrToPtr = %d\n", **ptrToPtr);
 
   getch();
   return 0;
}

Output

Value of count variable = 10
Value of count variable retreived uisng ptr 10
Value of count variable retreived uisng ptrToPtr = 10