C Program - C substring

#include <stdio.h>
#include <conio.h>
#include <malloc.h>
#include <stdlib.h>

char* substring(char*, int, int);

int main()
{
    char string[100], *pointer;
    int position, length;

    printf("Enter a string\n");
    gets(string);

    printf("Enter the position and length of substring\n");
    scanf("%d%d",&position, &length);

    pointer = substring( string, position, length);

    printf("Required substring is \"%s\"\n", pointer);

    free(pointer);
    getch();

    return 0;
}

/*C substring function: It returns a pointer to the substring*/

char *substring(char *string, int position, int length)
{
    char *pointer;
    int c;

    pointer = malloc(length+1);

    if (pointer == NULL)
    {
        printf("Unable to allocate memory.\n");
        exit(EXIT_FAILURE);
    }

    for (c = 0 ; c < position -1 ; c++)
        string++;

    for (c = 0 ; c < length ; c++)
    {
        *(pointer+c) = *string;
        string++;
    }

    *(pointer+c) = '\0';

    return pointer;
}

Output

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