Encryption of Affine Cipher

Affine Encryption

include<stdio.h>
#include<string.h>
# define MAX_EL 100
char ostr[MAX_EL]={0};
int main()
{
        int x,a,b,i;
        char c[MAX_EL]={0};
        printf("Enter a,b values\n");
        scanf("%d%d",&a,&b);
        //check for gcd(a,b);
        printf("Enter a string\n");
        if (getchar())
        {gets(c);}
        printf("The String is:%s\n",c);
        for(i=0;i<strlen(c);i++)
{
        {int x=c[i];
                if(x>=97 && x<=123)
                        {

                        printf("ascii val:%d\n",x);
                        calc(x,a,b,i);
                        }
                else
                        {
                        ostr[i]=c[i];
                        }
        }
}
puts(ostr);

}
int calc(int x, int a, int b,int i)
{
        int cipher;
         cipher=((a*x)+b) % 26;
        printf("Calculated value is:%d\n",cipher);
        if(cipher<97)
        {
                cipher=cipher+96;
        }
        printf("The values are:%d %d %d\n",a,x,b);
        printf("The encrpted output is:%d %c\n",cipher,cipher);
        ostr[i]=cipher;
}