#include <stdio.h>
int main(void)
{
int buffer; // An integer are declare
int *pointer; // A pointer to an integer are declared
buffer=512; // The buffer are set to 512
pointer=&buffer; // Pointer gets assigned the _adress_ that buffer points at
printf("Pointer points at [%i]\n",*pointer); // Print the content of whatever pointer points at
printf("Pointer contains [%i]\n",pointer); // Print the adress that pointer points at
printf("Buffer contains [%i]\n",buffer); // Print the content of the buffer
printf("Changing values\n"); // To demonstrate i change the value of buffer
// and reprint the values
buffer=1024;
printf("Pointer points at [%i]\n",*pointer); // Print the content of whatever pointer points at
printf("Pointer contains [%i]\n",pointer); // Print the adress that pointer points at
printf("Buffer contains [%i]\n",buffer); // Print the content of the buffer
printf("Changing values\n"); // To demonstrate once again
*pointer=2048; // We now want to change buffer by using the pointer
printf("Pointer points at [%i]\n",*pointer); // Print the content of whatever pointer points at
printf("Pointer contains [%i]\n",pointer); // Print the adress that pointer points at
printf("Buffer contains [%i]\n",buffer); // Print the content of the buffer
}
Generates following output:
bash-2.05b$ ./a.out
Pointer points at [512]
Pointer contains [-1073745188]
Buffer contains [512]
Changing values
Pointer points at [1024]
Pointer contains [-1073745188]
Buffer contains [1024]
Changing values
Pointer points at [2048]
Pointer contains [-1073745188]
Buffer contains [2048]
Whats it good for? Give me some examples!
Very simple example would be a sub-routine that does work on several values and returns more than one result, as follow:
#include <stdio.h>
int multi(ap,bp,cp) // Function that works on 3 pointers
int *ap,*bp,*cp;
{
int temp;
*ap=*bp + *cp; // add the values of c and b and store the result in a
temp=*bp; // Swap bp and bc
*bp=*cp;
*cp=temp;
}
int main(void)
{
// Practical exampel on use of pointers
int a,b,c;
a=b=c=0;
printf("Initated values\n");
printf("A:[%i] B:[%i] C:[%i]\n",a,b,c);
a=3;b=2;c=1; // Random test values
printf("\nRandom test values\n");
printf("A:[%i] B:[%i] C:[%i]\n",a,b,c);
multi(&a,&b,&c); // Calling function, passing on addresses for a,b and c
printf("\nAfter multi values\n");
printf("A:[%i] B:[%i] C:[%i]\n",a,b,c);
}
Generates following output:
bash-2.05b$ ./a.out
Initated values
A:[0] B:[0] C:[0]
Random test values
A:[3] B:[2] C:[1]
After multi values
A:[3] B:[1] C:[2]
