HASHING Linerar Probing

#include<stdio.h>
#include<stdlib.h>
#include<String.h>

int m;
int c;

int HashFn(int k,int i)
{
    return ((k+(i*c))%m);
}

int isfull(int *a)
{
    int i,f=0;
    for(i=0;i<m;i++)
    {
        if(a[i]!=-1)
        {
            f++;
        }
    }
    if(f==0)
    return 1;
    else
    return 0;
}

int isempty(int *a)
{
    int i,f=0;
    for(i=0;i<m;i++)
    {
        if(a[i]==-1)
        {
            f++;
        }
    }
    if(f==12)
    return 1;
    else
    return 0;
}
void printHash(int *a)
{
    int i;
    puts("index\t\tdata\n");
    for(i=0;i<m;i++)
    {

        if(a[i]==-1)
        printf("%d\t\t\n",i);
        else
        printf("%d\t\t%d\n",i,a[i]);
    }
}

void insert(int *a,int k)
{
    int i=0;
    int h=HashFn(k,i);
    while (a[h]!=-1)
    {
        if(isfull(a)==1)
        {
            printf("no space found ");
            break;
        }
        i++;
        h=HashFn(k,i);
    }
    a[h]=k;
    puts("data added successfully");

}

void search(int *a,int n1)
{
    int i=0;
    int h=HashFn(n1,i);
    while (a[h]!=n1)
    {
        i++;
        h=HashFn(n1,i);
        if(a[h]==n1)
        {
            printf("the data is present at position%d\n",h);
        }
        else
        {
            printf("not found !\n");
            break;
        }
    }
}

void Delete(int *a,int n1)
{
    int i=0;
    int h=HashFn(n1,i);
    while (a[h]!=n1)
    {
        if(isempty(a)==1)
        {
            printf("no space found ");
            break;
        }
        i++;
        h=HashFn(n1,i);
    }
    if(a[h]==n1)
    {
        a[h]=-1;
        printf("deleted\n");
    }
    else
    {
        printf("not found!\n");
    }
}

int main()
{
    int *a,i,n,ch;
    puts("enter m :");
    scanf("%d",&m);
    a=(int*) calloc(m,sizeof(int));
    puts("enter c :");
    scanf("%d",&c);

    for(i=0;i<m;i++)
    {
        a[i]=-1;
    }
    while(1)
    {
        puts("1>insert a key\n2> search key\n3> delete a key\n4>display the hash table\n5>exit\nenter your choice :");
        scanf("%d",&ch);
        switch(ch)
        {
            case 1:
                printf("enter the data :");
                scanf("%d",&n);
                insert(a,n);
            break;
            case 2:
                printf("the data you want ? :");
                scanf("%d",&n);
                search(a,n);
            break;
            case 3:
                printf("the data you want to delete ? :");
                scanf("%d",&n);
                Delete(a,n);
            break;
            case 4:
                printHash(a);
            break;
            case 5:
                exit(0);
            default:
                puts("invalid choice");
        }
    }
    return 0;
}