Why is int rather than unsigned int used for C and C++ for loops?

Question

This is a rather silly question but why is int commonly used instead of unsigned int when defining a for loop for an array in C or C++?

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Answer 1

Consider the following simple example:

int max = some_user_input; // or some_calculation_result
for(unsigned int i = 0; i < max; ++i)
    do_something;

If max happens to be a negative value, say -1, the -1 will be regarded as UINT_MAX (when two integers with the sam rank but different sign-ness are compared, the signed one will be treated as an unsigned one). On the other hand, the following code would not have this issue:

int max = some_user_input;
for(int i = 0; i < max; ++i)
    do_something;

Give a negative max input, the loop will be safely skipped.