c pointers

Question

main()
{
    char *p1="name";
    char *p2;
    p2=(char*)malloc(20);
    memset(p2,0,20);
    while(*p2++=*p1++);
    printf("%s\n",p2);
}

Comments

@akash, wat issues u have with dis code?

---

i can't able to crack the logic of method memset . help me

Answer 1

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main() {
	char *p1="name";
	char *p2;
	p2=(char*)malloc(20);
	memset(p2,0,20);
	
	char *temp = p2; // add this line of code
	                 // which stores the pointer location returned by malloc 
	while(*p2++=*p1++); // copy string content pointed by p1 to p2
	                    // in this process both p1 and p2 gets incremented
	printf("%s\n",temp);// temp still pointing to the start 
	                    // of newly created string 
}

Comments

memset line isnot required here .rt?

---

it Set 0 every place so yes not neccesory.

---

means?

---

memset works as Calloc() i.e. clear the memory. Memory previously allocated to some variable so it can contain some garbage value so memset will clear memory by setting Zero every place.

Answer 2

Improved Code:

Compiler DOS Box. 

#include<stdio.h>

#include<stdlib.h>

#include<conio.h>

#include<string.h>

void main()

{

  char *p1="name";

char *p2;

clrscr();

p2=(char *) malloc(20);

memset(p2,0,20);

while(*++p2=*p1++)

printf("%s\n",p2);

getch();

}

Comments

calloc() allocates the memory and also initializes the allocates memory to zero.

void * calloc( size_t num, size_t size );

calloc() takes two arguments: 1) number of blocks to be allocated 2) size of each block.

so We can achieve same functionality as calloc() by using malloc() followed by memset(),

ptr = malloc(size); memset(ptr, 0, size);

refer: http://www.geeksforgeeks.org/calloc-versus-malloc/

---

https://www.tutorialspoint.com/c_standard_library/c_function_memset.htm

Visit d above link. :)

---

Even without memset it is giving same output. :)