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Asked: 2026-05-26T08:12:48+00:00

I am attempting to convert a string into a number by summing the int

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I am attempting to convert a string into a number by summing the int value of each letter together in C++ WinAPI. So in ASCII; the std::string “AA” would equal 130 (65+65)

The string can either be a std::string or an std::wstring.

Why does the following function always return the value of zero no matter what letter I put in it? Shouldn’t it return either the ASCII or Unicode integer value of the letter?

printf("TEST a: %d \n", _tstoi(_T("a")));
printf("TEST A: %d \n", _tstoi(_T("A")));
printf("TEST b: %d \n", _tstoi(_T("b")));

My VC++ application is currently in Unicode, & the previous code prints out zero for each letter. I remember hearing that Unicode is very different to ASCII strings, can you clear up what exactly is different other than Unicode has a library of characters which is something like 30,000 long whilst ASCII is 256(I think?)?

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1 Answer

  1. Editorial Team

    the *toi family of functions converts a string representation to integer representation, that is, “10” becomes 10. What you actually want to do is no conversion at all. Change it to:

    printf("TEST a: %d \n", _T('a'));
printf("TEST A: %d \n", _T('A'));
printf("TEST b: %d \n", _T('b'));

    As for unicode, the underlying representation depends on the encoding ( for example UTF-8, which is very popular, maps the LSB with the ASCII table ).

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