Difference between char and int when declaring character

by

The difference is the size in byte of the variable, and from there the different values the variable can hold.

A char is required to accept all values between 0 and 127 (included). So in common environments it occupies exactly
one byte (8 bits). It is unspecified by the standard whether it is signed (-128 – 127) or unsigned (0 – 255).

An int is required to be at least a 16 bits signed word, and to accept all values between -32767 and 32767. That means that an int can accept all values from a char, be the latter signed or unsigned.

If you want to store only characters in a variable, you should declare it as char. Using an int would just waste memory, and could mislead a future reader. One common exception to that rule is when you want to process a wider value for special conditions. For example the function fgetc from the standard library is declared as returning int:

int fgetc(FILE *fd);

because the special value EOF (for End Of File) is defined as the int value -1 (all bits to one in a 2-complement system) that means more than the size of a char. That way no char (only 8 bits on a common system) can be equal to the EOF constant. If the function was declared to return a simple char, nothing could distinguish the EOF value from the (valid) char 0xFF.

That’s the reason why the following code is bad and should never be used:

char c;    // a terrible memory saving...
...
while ((c = fgetc(stdin)) != EOF) {   // NEVER WRITE THAT!!!
    ...
}

Inside the loop, a char would be enough, but for the test not to succeed when reading character 0xFF, the variable needs to be an int.

More Related Contents:

  1. Pointer manipulation inside function
  2. Please explain the following parallel code template
  3. Changing address contained by pointer using function
  4. Implicit type promotion rules
  5. Why isn’t the size of an array parameter the same as within main?
  6. Why is this string reversal C code causing a segmentation fault? [duplicate]
  7. C sizeof a passed array [duplicate]
  8. How do I create an array of strings in C?
  9. A Makefile with Multiple Executables
  10. Redirecting exec output to a buffer or file
  11. clock_gettime alternative in Mac OS X
  12. What is the instruction that gives branchless FP min and max on x86?
  13. Please explain the exec() function and its family
  14. What are the use cases of SO_REUSEADDR?
  15. How to measure program execution time in ARM Cortex-A8 processor?
  16. How can I copy a file on Unix using C?
  17. How to replicate vector in c?
  18. How to kill processes by name? (Win32 API)
  19. Bitwise rotate left function
  20. Why getch() returns before press any key?
  21. Is it safe to use variable-length arrays?
  22. Order of operations for pre-increment and post-increment in a function argument? [duplicate]
  23. Why is adding a leading space in a scanf format string recommended?
  24. sqrt from math.h causes linker error “undefined reference to sqrt” only when the argument is not a constant
  25. Append to the end of a file in C
  26. How to flush the CPU cache for a region of address space in Linux?
  27. addr2line on kernel module
  28. Is there a way to get the filename from a `FILE*`? [duplicate]
  29. Can I compare int with size_t directly in C?
  30. Infinite recursion in C

Leave a Comment