C Programming - Pointers - Discussion

Since we know that decleration+initialization=can we write.

I want to explain brief discription about the char that char represents a individual value during coding in c language i.e. p in above code,as we can also write as char p = malloc(100);

Please can an one explain malloc and calloc function ?

malloc & calloc both are memory allocation function & both returns void type where afterwords we type case it.

ex:

int *p;
p=(int*)malloc(1000);

where malloc depends upon byte which are fixed i.e 8-bit,again 16-bit.

calloc deals with no.of bytes where bytes is considered as block relevant to the memory issue.

1. char p;
p= (char *) malloc (1000) ;

2. char *p;
p= (char *) malloc (1000) ;

Is that 1 and 2 mean the same. explain?

#include<stdio.h>
int main(){
int i=320;
char *ptr=(char*)&i;
printf("%d",*ptr);
return 0;
}

Ans: 64.

Could anyone explain this program and answer?.

Here the memory is allocated by malloc function. P is local variable so the memory is allocated on stack for P. But the memory allocated by malloc function is 100 byte and which is allocated on HEAP. Here the type of pointer is character so for allocating the memory malloc is type casted with character, Because malloc always returns void*.

So void* is a pointer which pointing to particular address but can not access the element from that address. For allocating memory malloc internally call sbrk and brk algorithm. This algorithm internally called by growrage algorithm.

Say: int a=10;

// This means a is a variable where 10 is stored.

Now say the address/ memory location of a is 5000.

So, I say: int *a= 5000;

// 5000 refers to the memory location of a or pointed to a.

Hence

For storing a value you need a definition statement and for storing a memory address you need a pointer.

char *p;

Here *p means value of p.

And p= (char *) malloc (1000); which is saying that value of p is char*..

Therefore,

They can be combined as:

char *p = (char *) malloc (1000);

If p is a pointer.

i.e. p addressing some variable for eg x.

The p stores the address of x.

And *p gives the value of x. Is this correct or not?