Differential coding

#include<stdio.h>

#include<conio.h>

int main()

{

    int n,num,i,regester=0,ascii[20],encoding[20],bitrequired,reducedbit=0;

    char str[20];

    printf("enter the size of characters\n");

    scanf("%d",&n);

    bitrequired=7*n;

    printf("enter %d characters\n",n);

    for(i=0;i<n;i++)

    scanf("%s",&str[i]);

    for(i=0;i<n;i++)

    {

                    num=str[i];

                    ascii[i]=num;

    }

    for(i=0;i<n;i++)

    {

                    encoding[i]=ascii[i]-regester;

                    regester=ascii[i];

    }

    printf("encoded numbers are\n\n");

    for(i=0;i<n;i++)

    {

            printf("%d\t",encoding[i]); 

            num=encoding[i];

            if(num<=127 && num>63)

            reducedbit=reducedbit+7;

            else if(num<=63 && num>31)

            reducedbit=reducedbit+6;

             else if(num<=31 && num>15)

            reducedbit=reducedbit+5;

             else if(num<=15 && num>7)

            reducedbit=reducedbit+4;

             else if(num<=7 && num>3)

            reducedbit=reducedbit+3;

             else if(num<=3 && num>1)

            reducedbit=reducedbit+2;

            else

            reducedbit++;       

              

    }

    printf("required bit=%d\n",bitrequired);

    printf("reduced bit = %d",reducedbit);

    getch();

}