Conversion of other base system to decimal(floating and normal).

FLOAT_ALL_TO_DEC.CPP

#include<iostream>
#include<string.h>
#include<math.h>
#include<cctype>
using namespace std;
int bd[30],ad[30],l_bd,l_ad,flag;
void change(char a[30],int n,int base)
{
    int i=0,j=0;
    while(a[i]!='.'&&i<n)
    {
        if(base==16)
        {
            if(isalpha(a[i]))
            {
                bd[j]=((int)tolower(a[i])-87);
                i++;
            }
            else
            {
                bd[j]=((int)a[i]-48);
                i++;
            }
        }
        else
        {
            bd[i]=((int)a[i]-48);
            i++;
        }
    }
    int k=0;flag=1;
    if(base==8||base==2)
    {
        while(k<n)
        {
            if((int)(bd[k])>=base)
            {
                flag=0;
                k++;
            }
            else{k++;}
        }
    }
    else
    {
        while(k<n)
        {
            if((int)((bd[k]))>=base)
            {
                flag=0;
                k++;
            }
            else{k++;}
        }
    }
    if(flag==0){cout<<"Enter Valid Input"<<endl;}
    else
    {
        for(int j=0;j<i;j++)
        {
            cout<<bd[j]<<"\t";
        }
        l_bd=i;
        while(i+1<n)
        {
            if(base==16)
            {
                if(isalpha(a[i+1]))
                    ad[j]=((int)tolower(a[i+1])-87);
                else
                {
                    ad[j]=((int)a[i+1]-48);
                }
                i++;
                j++;
            }
            else
            {
                ad[j]=((int)a[i+1]-48);
                i++;
                j++;
            }
        }
        l_ad=j;
        cout<<".";
        for(int i=0;i<j;i++)
        {
            cout<<ad[i];
        }
    }
}
void convert(int bd[30],int ad[30],int base)
{
    int s=0;
    float s_t=0;
    for(int i=0,j=l_bd-1;i<l_bd,j>=0;i++,j--)
    {
        s=s+(pow(base,i)*(bd[j]));
    }
    for(int i=1;i<l_ad+1;i++)
    {
        s_t=s_t+(pow(base,-i)*(ad[i-1]));
    }
    s_t=s+s_t;
    if(!flag==0)
    {
        cout<<"\nThe decimal number will be : "<<s_t<<endl;
    }
}
int main()
{
    char a[30],ch;int n,base;
    do
    {
        cout<<"Enter base to which you want to convert : ";
        cin>>base;
        cout<<"Enter number "<<endl;
        cin>>a;
        n=strlen(a);
        change(a,n,base);
        convert(bd,ad,base);
        cout<<"\nTo continue press y"<<endl;
        cin>>ch;
    }while(ch=='y');
    return 0;
}