2.12.1 Variables and Definitions

size_t is the unsigned integer result of the sizeof keyword.
FILE is a type suitable for storing information for a file stream.
fpos_t is a type suitable for storing any position in a file.

NULL is the value of a null pointer constant.
_IOFBF_IOLBF, and _IONBF are used in the setvbuf function.
BUFSIZ is an integer which represents the size of the buffer used by the setbuf function.
EOF is a negative integer which indicates an end-of-file has been reached.
FOPEN_MAX is an integer which represents the maximum number of files that the system can guarantee that can be opened simultaneously.
FILENAME_MAX is an integer which represents the longest length of a char array suitable for holding the longest possible filename. If the implementation imposes no limit, then this value should be the recommended maximum value.
L_tmpnam is an integer which represents the longest length of a char array suitable for holding the longest possible temporary filename created by the tmpnam function.
SEEK_CURSEEK_END, and SEEK_SET are used in the fseek function.
TMP_MAX is the maximum number of unique filenames that the function tmpnam can generate.
stderrstdin, and stdout are pointers to FILE types which correspond to the standard error, standard input, and standard output streams.