atoi conversion problem

[fantastic4]

Following code is not working properly
it give answer
c=5
and
d=75

char a='5',b='7';
int c,d;
c=atoi(&a);
cout<<c;
d=atoi(&b);
cout<<d;

[jkmyoung]

Seems like it's looking at the address and expecting a string; however you have only defined space for characters.
In memory, it must be stored as
75\0.

Use strings instead of single chars, or you could also try c=(int)(a - '0');
since you know both a and b are chars.

[donbock]

Refer to the man page for atoi. As jkmyoung said, atoi expects its argument to point to a null-terminated string. That's not what you passed. It is amazing the result bears any resemblance to what you expect.

[whodgson]

The following may shed some further light on it.

const char* s="  21xy 3";
    const char*s1= " 74.7xyz ";
    cout<<"the first string is \n"<<s<<endl;
    cout<<"the second string is \n"<<s1<<endl;
    n=atoi(s);
    m=atoi(s1);
    cout<<"after converting strings to integers ";
    cout<<"s= "<<n<<" and s1="<<m<<endl;
    cout<<"the product of s and s1 is "<<n*m<<endl; 

//prints:-
/*demonstrating the atoi() function
the first string is
21xy 3
the second string is
74.7xyz
after converting strings to integers s= 21 and s1=74
the product of s and s1 is 1554
press any key to continue...*/

[whodgson]

The following convert() function I think does the equivalent of atoi ().

double convert(string a)
{double sum_s=0.0;
    double xx=0.0;
    len=a.length();
    n=len;
    xx=pow(10,n-1);
    for(int i=0;i<len;i++)
    {
    sum_s+=(a[i]-'0')*xx;
    xx/=10;
    }
    return sum_s;
}