Assignment 2 :Dynamic memory allocation in C.

Assignment 2: Dynamic memory allocation in C.

•  Dynamic Memory Allocation is manual allocation and freeing of memory according to your programming needs. 
• Dynamic memory is managed and served with pointers that point to the newly allocated memory space in an area which we call the heap.
• Now you can create and destroy an array of elements dynamically at runtime without any problems. To sum up, the automatic memory management uses the stack, and the C Dynamic Memory Allocation uses the heap.
• The <stdlib.h> library has functions responsible for Dynamic Memory Management.

1. malloc() :- Allocates the memory of requested size and returns the pointer to the first byte of allocated space.

            The syntax of malloc() function is given below:

            ptr=(cast-type*)malloc(byte-size)  

    2. calloc() :- Allocates the space for elements of an array. Initializes the elements to zero                                 and returns a pointer to the memory.

            The syntax of calloc() function is given below:

            ptr=(cast-type*)calloc(number, byte-size)  

    3.  realloc() :- It is used to modify the size of previously allocated memory space.

            The syntax of realloc() function.

            ptr=realloc(ptr, new-size) 

    4. Free() :- Frees or empties the previously allocated memory space.

            The syntax of free() function.

                free(ptr)  

Example:-

#include<stdio.h>  

#include<stdlib.h>  

int main(){  

  int n,i,*ptr,sum=0;    

    printf("Enter number of elements: ");    

    scanf("%d",&n);    

    ptr=(int*)malloc(n*sizeof(int));  //memory allocated using malloc    

    if(ptr==NULL)                         

    {    

        printf("Sorry! unable to allocate memory");    

        exit(0);    

    }    

    printf("Enter elements of array: ");    

    for(i=0;i<n;++i)    

    {    

        scanf("%d",ptr+i);    

        sum+=*(ptr+i);    

    }    

    printf("Sum=%d",sum);    

    free(ptr);     

return 0;  

}    

/*********************************************************/

Output

Enter elements of array: 3

Enter elements of array: 10

10

10

Sum=30

/*****************************************************/

1. Write a program to  accept N integers and store them dynamically and access them.

Program :-

#include<stdio.h>  

#include<stdlib.h>  

void main()

{

int *p, n,i;

printf(“How many elements :”);

scanf(“%d”,&n);

p = (int *)malloc(n*sizeof(int));

/* Accepting data */

for(i=0; i<n;i++)

scanf(”%d”,p+i);

/* Displaying data */

for(i=0; i<n;i++)

printf(”%d\t”,*(p+i));

}

2. Program :-

 #include<stdio.h>

#include<stdlib.h>

main()

{

 int *a[10],r,c,i,j;

printf("Enter the order of matrix\n");

scanf("%d%d",&r,&c);

printf("Enter matrix elements\n");

 for(i=0;i<r;i++)

 {

 /**** dynamically allocate memory for every row ****/

 a[i]=(int *)malloc(c*sizeof(int));

 for(j=0;j<c;j++)

 {

scanf("%d",a[i]+j);

 }

 }

 /****** Display Matrix ******/

printf("The matrix is as below\n");

 for(i=0;i<r;i++)

 {

 for(j=0;j<c;j++)

 {

printf("%d\t",*(*(a+i)+j));

 }

printf("\n");

 }

}

3. Write a program to accept N integers and store them dynamically display them in 

reverse order.

Program :-

#include <stdio.h>

#include <stdlib.h>

int main()

{

    int i, max;

    int *ptr;

    // Input maximum elements of array

    printf("Enter total number of elements: ");

    scanf("%d", &max);

    

    // Allocate memory for 'max' integer elements and initialized to 0 

    ptr = (int *) calloc(max, sizeof(int));

    

    // If memory not allocated

    if(ptr == NULL)

    {

        printf("Memory is not created!!!");

        exit(0); // Exit from the program

    }

    

    // Input elements from user

    printf("Enter %d elements: \n", max);

    for (i = 0; i < max; i++)

        scanf("%d", (ptr + i));

    

    // Print all elements 

    printf("\nArray elements are:\n");

    for (i =max; i >=0; i--)

        printf("%d ", *(ptr + i));

    

    // Release allocated memory

    free(ptr);

    

    return 0;

}

4. Write a program to allocate memory dynamically for n integers such that the memory is 

initialized to 0. And display it.

Program :-

#include <stdio.h>

#include <stdlib.h>

int main()

{

    int i, max;

    int *ptr;

    // Input maximum elements of array

    printf("Enter total number of elements: ");

    scanf("%d", &max);

    

    // Allocate memory for 'max' integer elements and initialized to 0 

    ptr = (int *) calloc(max, sizeof(int));

    

    // If memory not allocated

    if(ptr == NULL)

    {

        printf("Memory is not created!!!");

        exit(0); // Exit from the program

    }

    

    // Input elements from user

    printf("Enter %d elements: \n", max);

    for (i = 0; i < max; i++)

        scanf("%d", (ptr + i));

    

    // Print all elements 

    printf("\nArray elements are:\n");

    for (i = 0; i < max; i++)

        printf("%d  ", *(ptr + i));

    

    // Release allocated memory

    free(ptr);

    

    return 0;

}

1. Accept N integers in an array using dynamic memory allocation. Find maximum from them

and display.

Program:-

#include <stdio.h>

#include <stdlib.h>

int main() {

  int n;

  double *data;

  printf("Enter the total number of elements: ");

  scanf("%d", &n);

  // Allocating memory for n elements

  data = (double *)calloc(n, sizeof(double));

  if (data == NULL) {

  printf("Error!!! memory not allocated.");

  exit(0);

  }

  // Storing numbers entered by the user.

  for (int i = 0; i < n; ++i) {

  printf("Enter number%d: ", i + 1);

  scanf("%lf", data + i);

  }

  // Finding the largest number

  for (int i = 1; i < n; ++i) {

    if (*data < *(data + i)) {

      *data = *(data + i);

    }

  }

  printf("Largest number = %.2lf", *data);

  free(data);

  return 0;

}

2. Accept n integers in an array. Copy only the non-zero elements to another array 

(allocated using dynamic memory allocation). Calculate the sum and average of non zero elements.

Program:-

#include <stdio.h>

#include <stdlib.h>

int main()

{

    int i;

    int count;

    int *arr ,*arr1;

    int sum = 0;

    float avg=0.0;

    printf("Enter the total number of elements you want to enter : ");

    scanf("%d", &count);

    arr = (int *)malloc(count * sizeof(int));

for (i = 0; i < count; i++)

    {

        printf("Enter element %d : ", (i + 1));

        scanf("%d", arr + i);

    }

for (i = 0; i < count; i++)

    {

       if(*(arr+i)!=0)

*(arr1+i)=*(arr+i);

    }

    for (i = 0; i < count; i++)

    {

           sum += *(arr1 + i);

    }

    printf("sum is %d \n", sum);

    avg=sum/count;

     printf("Avg is %d \n", avg);

    free(arr);

    return 0;

}

3. Accept a matrix of order mXn (Use dynamic memory allocation and array of pointers

concept). Display trace of the matrix.

Program:-

#include<stdio.h>

#include<stdlib.h>

int main()

{

      int **a, row,col,i,j,t=0;

      printf("Enter Limit for Rows : ");

      scanf("%d",&row);

      printf("\nEnter Limit for Columns : ");

      scanf("%d",&col);

      a=(int **)malloc(row*sizeof(int*));

      for(i=0;i<row;i++)

      {

            a[i]=(int *)malloc(col*sizeof(int));

      }

      printf("\nEnter Elements for Matrix of Size %d*%d:\n\n",row,col);

      for(i=0;i<row;i++)

      {

            for(j=0;j<col;j++)

            {

                  scanf("%d",&a[i][j]);

            }

      }

      printf("\n%d*%d Matrix : \n\n",row,col);

      for(i=0;i<row;i++)

      {

            for(j=0;j<col;j++)

            {

                  printf("%3d ",a[i][j]);

            }

      printf("\n");

      }

      for(i=0;i<row;i++)

      {

            for(j=0;j<col;j++)

            {

if (i == j)

                   t=t+a[i][j];

            }

      }

      printf("\nTrace of Matrix = %d",t);

      return 0;

}

4. Accept a matrix of order mXn (Use dynamic memory allocation and array of pointers 

concept). Display Column wise sum of elements.

Program:-

#include<stdio.h>

#include<stdlib.h>

int main()

{

      int **a, row,col,i,j,t=0;

int rsum=0,csum=0;

      printf("Enter Limit for Rows : ");

      scanf("%d",&row);

      printf("\nEnter Limit for Columns : ");

      scanf("%d",&col);

      a=(int **)malloc(row*sizeof(int*));

      for(i=0;i<row;i++)

      {

            a[i]=(int *)malloc(col*sizeof(int));

      }

      printf("\nEnter Elements for Matrix of Size %d*%d:\n\n",row,col);

      for(i=0;i<row;i++)

      {

            for(j=0;j<col;j++)

            {

                  scanf("%d",&a[i][j]);

            }

      }

      printf("\n%d*%d Matrix : \n\n",row,col);

      for(i=0;i<row;i++)

      {

            for(j=0;j<col;j++)

            {

                  printf("%3d ",a[i][j]);

            }

      printf("\n");

      }

    printf("\nRow Sum....\n");

    for(i=0;i<row;i++)   

    {

        

        for(j=0;j<col;j++)

        {

            rsum=rsum+a[i][j];

        }

        printf("\nSum of all the elements in row %d is %d\n",i,rsum);

    }

    printf("\nColumn Sum....\n");

    for(i=0;i<row;i++)

    {

        

        for(j=0;j<col;j++)

        {

            csum=csum+a[j][i];

        }

        printf("\nSum of all the elements in column %d is %d\n",i,csum);

    }

}

Set A . Write C programs for the following problems.

1. Write a program to allocate memory dynamically for n integers such that the memory is initialized to 0. Accept the data from the user and find the range of the data elements.

 

#include <stdio.h>

#include <stdlib.h>

int main()

{

 int i, max;

 int *ptr;

 // Input maximum elements of array

 printf("Enter total number of elements: ");

 scanf("%d", &max);

 // Allocate memory for 'max' integer elements and initialized to 0

 ptr = (int *) calloc(max, sizeof(int));

 // If memory not allocated

 if(ptr == NULL)

 {

 printf("Memory is not created!!!");

 exit(0); // Exit from the program

 }

 // Input elements from user

 printf("Enter %d elements: \n", max);

 for (i = 0; i < max; i++)

 scanf("%d", (ptr + i));

 // Print all elements

 printf("\nArray elements are:\n");

 for (i = 0; i < max; i++)

 printf("%d ", *(ptr + i));

 // Release allocated memory

 free(ptr);

 return 0;

}

 

 

2. Accept n integers in an array. Copy only the non-zero elements to another array (allocated using dynamic memory allocation). Calculate the sum and average of non-zero elements.

#include <stdio.h>

#include <stdlib.h>

int main()

{

 int i;

 int count;

 int *arr ,*arr1;

 int sum = 0;

 float avg=0.0;

 printf("Enter the total number of elements you want to enter : ");

 scanf("%d", &count);

 arr = (int *)malloc(count * sizeof(int));

for (i = 0; i < count; i++)

 {

 printf("Enter element %d : ", (i + 1));

 scanf("%d", arr + i);

 }

for (i = 0; i < count; i++)

 {

if(*(arr+i)!=0)

*(arr1+i)=*(arr+i);

}

 for (i = 0; i < count; i++)

 {

sum += *(arr1 + i);

 }

 printf("sum is %d \n", sum);

 avg=sum/count;

printf("Avg is %d \n", avg);

 free(arr);

 return 0;

}

Set B . Write C programs for the following problems.

1. Accept the number of rows (m) and columns (n) for a matrix and dynamically allocate memory for the matrix. Accept and display the matrix using pointers. (Hint: Use an array of pointers.)

#include<stdio.h>

#include<stdlib.h>

int main()

{

 int **a, row,col,i,j,t=0;

 printf("Enter Limit for Rows : ");

 scanf("%d",&row);

 printf("\nEnter Limit for Columns : ");

 scanf("%d",&col);

 a=(int **)malloc(row*sizeof(int*));

 for(i=0;i<row;i++)

 {

 a[i]=(int *)malloc(col*sizeof(int));

 }

 printf("\nEnter Elements for Matrix of Size %d*%d:\n\n",row,col);

 for(i=0;i<row;i++)

 {

 for(j=0;j<col;j++)

 {

 scanf("%d",&a[i][j]);

 }

 }

 printf("\n%d*%d Matrix : \n\n",row,col);

 for(i=0;i<row;i++)

 {

 for(j=0;j<col;j++)

 {

 printf("%3d ",a[i][j]);

 }

 printf("\n");

 }

return 0;

}