basic c++ variable types, digits of precision etc

This is a discussion on basic c++ variable types, digits of precision etc within the C++ Programming forums, part of the General Programming Boards category; Hi Please have a look on this table: http://img192.imageshack.us/img192/4...ledatatype.jpg "int" is system dependent and on 32-bit system occupies four bytes. ...

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    basic c++ variable types, digits of precision etc

    Hi

    Please have a look on this table:
    http://img192.imageshack.us/img192/4...ledatatype.jpg

    "int" is system dependent and on 32-bit system occupies four bytes. As there are 8 bits in one byte therefore there are total 32 bits. If 2 is raised to the power of 32, 2^(32), it comes to 4294967296 which is equal to combined numerical range of int (2,147,483,648 + 2,147,483,647). The same is true for other variable types except "float" and "double". Why is so?

    Is "float" also system dependent like "int?

    What does the digits of precision, 7 and 15, for "float" and "double" respectively mean? Does this mean decimal point is followed by 7 and 15 digits respectively?

    It would be very nice of you if you would help me with the above queries. Please keep the things simple.

    Regards
    Jackson
    I'm an outright beginner. Using Win XP Pro and Code::Blocks. Be nice to me, please.

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    and the hat of int overfl Salem's Avatar
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    > Is "float" also system dependent like "int?
    Yes, but variation is less common. The C standard follows what IEEE defines, which in turn is what comes available in hardware FPU's. There is always scope to implement a float with more bits allocated to it, but it would be a lot of work for the implementer.

    > Does this mean decimal point is followed by 7 and 15 digits respectively?
    No, it means the left-most N digits (regardless of the decimal point)
    So
    123456789
    123.456789
    0.000123456789
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    The floating point variables have a more complex representation. But if you study how they are represented you can then understand where those numbers come from.

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    Algorithm Dissector iMalc's Avatar
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    Floating point essentially uses scientific notation.
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