What are pointers?
Today, my young nephew came to me with the question "What is that thing called 'pointers' in the C programming language?" from his first programming course at school.
The time has come to see if he was born with that part of the brain that understands pointers. After some minutes of explanation, I presented to him the following 4 programs asking him "What is displayed in the screen for each program?"
He answered correctly all of them, and I concluded that such part of the brain is present indeed.
Program 0:
#include <stdio.h>
void main()
{
char n;
n=65;
printf("%d\n",n);
char* p;
p= &n;
printf("%d\n", *p );
char* g=p;
printf("%d\n", *g );
*g=14;
printf("%d\n", n );
printf("%d\n", *p );
printf("%d\n", *g );
}
Program 1:
#include <stdio.h>
void f(int x)
{
x= x * 2;
}
void g(int* x)
{
*x= (*x) * 2;
}
void main()
{
int n=30;
f(n);
printf("n=%d\n",n);
g(&n);
printf("n=%d\n",n);
}
Program 2:
#include <stdio.h>
float* f(float* x, float* y)
{
*x= (*x) * (*y);
return y;
}
void main()
{
float n = 4;
float m = 2;
float* r = f(&n,&m);
printf("result=%f \n", n);
printf("result=%f \n", *r);
}
Program 3:
#include <stdio.h>
char f(char* x, char y)
{
char result=( (*x) + y ) / 2;
return result;
}
char* g(char* s, char* t)
{
*s = *t;
return s;
}
void main()
{
char a=65;
char b=90;
char c=f(&a,b);
printf("%c \n", c);
void* n=(void*)g(&a, &b);
printf("%x \n", n);
}
