Why does sizeof(int) vary across different operating systems?

by

Why so?

Historical reasons.

Before the advent of the ANSI C standard and size_t in 1989, int was the type used to index into arrays. malloc took an int as its argument, strlen returned one. Thus int had to be large enough to index any array, but small enough to not cause too much overhead. For file offsets, typically a larger type such as long was typedef‘d to off_t.

On the PDP-11 were C was first implemented in the early 1970s, int was as large as a processor register: 16 bits. On larger machines such as the VAX, it was widened to 32 bits to allow for larger arrays.

This convention has been largely abandoned; the C and C++ standards use size_t and ssize_t for indices and lenghts of arrays. On 64-bit platforms, often int is still 32 bits wide while size_t is 64 bits. (Many older APIs, e.g. CBLAS, still use int for indices, though.)

More Related Contents:

  1. C/C++ maximum stack size of program on mainstream OSes
  2. Programmatically get the cache line size?
  3. What happens when a computer program runs?
  4. Determine Process Info Programmatically in Darwin/OSX
  5. Spinlock versus Semaphore
  6. Are there any macros to determine if my code is being compiled to Windows? [duplicate]
  7. Ctrl + C interrupt event handling in Linux
  8. Is it possible to use threads to speed up file reading?
  9. System() calls in C++ and their roles in programming
  10. Unterminating c++ Program [closed]
  11. Accessing an array out of bounds gives no error, why?
  12. Pure virtual function with implementation
  13. How to “return an object” in C++?
  14. Which is faster: Stack allocation or Heap allocation
  15. Best C++ Code Formatter/Beautifier
  16. Fast ceiling of an integer division in C / C++
  17. Visual Studio 2015 “non-standard syntax; use ‘&’ to create a pointer to member”
  18. What C/C++ compiler can use push pop instructions for creating local variables, instead of just increasing esp once?
  19. Sort a 2D array in C++ using built in functions(or any other method)?
  20. What does the ‘L’ in front a string mean in C++?
  21. Number of combinations (N choose R) in C++
  22. Error: cannot bind non-const lvalue reference of type ‘int&’ to an rvalue of type ‘int’
  23. How to use C++11 uniform initialization syntax?
  24. The Pimpl Idiom in practice
  25. Modifying a char *const string
  26. Can macros be overloaded by number of arguments?
  27. Passing Variable Number of Arguments with different type – C++
  28. How to iterate std::set?
  29. Duplicate const qualifier allowed in C but not in C++?
  30. Find available network interfaces in C/C++? [closed]

Leave a Comment