C Tutorial - About Pointers

// ex4.c
//
#include <stdio.h>
#define numitems 50
int main(int argc, char* argv[])
{
    
   int data[numitems];
   int *ptr;

   for(ptr = data; ptr < &data[numitems]; ptr++)
      *ptr = 0;
    return 0;
}

Example 5. You might recognise a version of this from this C Programming Problem blog entry as an example of code with errors in it. This is the correct version.

// ex5.c
//
#include <stdlib.h>

#define maxitems 1000
typedef int vector[maxitems];

int * addvectors(int * v1,int * v2) {
    int index;
    int * result = (int *) malloc(sizeof(vector)) ;
    int * temp=result;
    for (index =0;index < maxitems;index++)
        (*temp++)= *v1++ + *v2++;
    return result;
}

int main(int argc, char* argv[])
{
    vector a,b;
    int *c;
    int index;
    for( index=0; index < maxitems; index++){
       a[index]=10+index;
       b[index]= index*1000;
    }
    
    c= addvectors((int *)a,(int *)b) ;
    free(c) ;
    return 0;
}

On the Next Page : A complicated example. Slightly trimmed to fit!

• Learn About Pointers
• Allocating Memory
• Explanation of Example 1 Continued
• Explanation of Example 1 Continued
• Examples of Pointers
• Example 2- Using Pointers with a Struct
• About malloc and free
• Some Rules for Working with Pointers
• Some More Examples of Pointers in C
• Example of 2D Structure with Pointers