c pointers

1#include <stdio.h>
2int main() {
3   int c = 5;
4   int *p = &c;
5
6   printf("%d", *p);  // 5
7   return 0; 
8}

1#include<stdio.h>
2
3/*
4	'*' is the dereference operator; it will grab the value at a memory address.
5    	it is also used to declare a pointer variable.
6    
7    '&' is the address-of operator; it will grab the memory address of a variable.
8*/
9
10int main(int argc, char *argv[]) {
11	int x = 45;			// Declare integer x to be 45.
12    int *int_ptr = &x;	// int_ptr now points to the value of x.  Any changes made to the value at int_ptr will also modify x.
13  	
14  	x = 5;				// Now, the value of x is 5.  This means that the value at int_ptr is now 5.
15  	*int_ptr = 2;		// Now, the value at int_ptr is 2.  This means that x is now 0.
16  	int_ptr = NULL;		// int_ptr now no longer points to anything.  Make sure you never leave a dangling pointer!
17    
18    return 0;
19}

1int* pc, c, d;
2c = 5;
3d = -15;
4
5pc = &c; printf("%d", *pc); // Output: 5
6pc = &d; printf("%d", *pc); // Ouptut: -15

1datatype *var;
2
3variable var actually holds the address of the data(memory where it is stored)
4*var lets you access the data stored at that address

1int c, *pc;
2
3// pc is address but c is not
4pc = c; // Error
5
6// &c is address but *pc is not
7*pc = &c; // Error
8
9// both &c and pc are addresses
10pc = &c;
11
12// both c and *pc values 
13*pc = c;

1myvar = 25;
2foo = &myvar;
3bar = myvar;