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POC/C++: sizeof(short), sizeof(int), sizeof(long), sizeof(long long), etc... on a 32-bit machine versus on a 64-bit machine
 

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  1. POC/C++: sizeof(short), sizeof(int), sizeof(long), sizeof(long long), etc... on a 32-bit machine versus on a 64-bit machine
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    <p>I'm running Windows 7 (64-bit).</p> <p>This question looks at the same question found here:</p> <p><a href="https://stackoverflow.com/questions/660372/long-on-a-64-bit-machine">long on a 64 bit machine</a></p> <p>but is more in-depth as it deals with even more data types and applies to C or C++, not C#. First of all, I am using Microsoft Visual Studio Ultimate 2012. Unfortunately, while this IDE supports C# and Visual C++ it no longer supports plain old Visual C it seems. Anyhow, I've tried the creating the following standard C++ program in the IDE:</p> <pre><code>#include &lt;cstdio&gt; int main(int argc, char **argv) { printf("sizeof(short): %d\n", (int) sizeof(short)); printf("sizeof(int): %d\n", (int) sizeof(int)); printf("sizeof(long): %d\n", (int) sizeof(long)); printf("sizeof(long long): %d\n", (int) sizeof(long long)); printf("sizeof(size_t): %d\n", (int) sizeof(size_t)); printf("sizeof(void *): %d\n", (int) sizeof(void *)); printf("Hit enter to exit.\n"); char *scannedText; scanf("%s", &amp;scannedText); return 0; } </code></pre> <p>and since I couldn't find the option to run a console application I simply placed a breakpoint at the "return 0;" statement, so as to view the output in the console. The result was:</p> <pre><code>sizeof(short): %d\n", 4 sizeof(int): %d\n", 4 sizeof(long): %d\n", 4 sizeof(long long): 8 sizeof(size_t): 4 sizeof(void *): 4 Hit enter to exit. </code></pre> <p>Old C textbooks state that int is set to the "word size", which is 16 on 16-bit machines and 32 on 32-bit machines. However this rule seems to break on 64-bit systems where one would expect the "word size" to be 64. Instead, from what I've read these systems are like 32-bit systems but have better support for 64-bit computations than their 32-bit counterparts did. Hence, the results obtained from the above C++ program are exactly the same as one would obtain on a 32-bit system. The size of data types (size_t) (which can be used to measure amount of memory taken up by objects in memory) also stores its values in 4 bytes, and it is also interesting that the size of pointers used to access memory locations (for instance sizeof(void *) shows the number of bits used to store generic pointers to any location in memory) is also 32 bits long.</p> <p>Anyone know how come Visaul C was removed from Visual Studio 2012 and whether it is still possible to run console applications from Visual Studio 2012 without having to set a breakpoint or read text from standard input prior to exiting as above in order for the console window to pause before closing?</p> <p>Furthermore, is my interpretation correct, or do I have something misconfigured in the IDE so that, for instance, it compiles for 32-bit rather than for 64-bit systems? According to one of the poster, since my system is 64-bit, I should see the results described here for size_t and pointers: <a href="https://en.wikipedia.org/wiki/64-bit_computing#64-bit_data_models" rel="nofollow noreferrer">https://en.wikipedia.org/wiki/64-bit_computing#64-bit_data_models</a> but I am not seeing this. Is there a way to reconfigure Visual Studio so that it may support a 64-bit memory model, as opposed to what I am currently seeing in the program's output?</p> <p>Thanks.</p>
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    1. USJohn Sonderson
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      1. POC/C++: sizeof(short), sizeof(int), sizeof(long), sizeof(long long), etc... on a 32-bit machine versus on a 64-bit machine
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    1. COVisual Studio uses the [LLP64 model](https://en.wikipedia.org/wiki/64-bit_computing#64-bit_data_models) on 64-bit machines.
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      1. USAdam Rosenfield
    2. COsizeof(int *) would be a good addition to your list to help understand 64 bit machines.
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      1. POC/C++: sizeof(short), sizeof(int), sizeof(long), sizeof(long long), etc... on a 32-bit machine versus on a 64-bit machine
      1. USCharlie Burns
    3. COC support was *not* removed. What you see happening in your console app is the exact same thing that happens when you create a shortcut on your desktop to your program. Flash, bang, gone. You'll have to add the proverbial "Hit any key to continue" code. Using 8-byte integers would make 64-bit code very slow. The constraint is not the processor, it is memory. It isn't any faster in 64-bit mode. Ask only *one* question.
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      1. USHans Passant
 

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