gets(*char var) read one line of text and pass to char array, not 0–> not end, NULL–> end int c, string is a char arry terminated by a NULL, for example, “hello”–>h e l l o NUL
printf format
%d Print an integer value in decimal.
%o Print an integer value in octal.
%x Print an integer value in hexadecimal.
%g Print a floating point value.
%c Print a character.
%s Print a character string.
\n Print a newline.
EXIT_FAILURE & EXIT_SUCCESS in stdlib. 0 for success, 1 for fail
intinial value for “int i;” i will be a unpredictable value.
%d stop at “ “