KING

First is the basic

• About #
  • these code are processed by the preprocessor
  • After the preprocessor read the code, the preprocessor directives will deal with it
  • then give the main code that are dealed with by the preprocessor directives to the complier
  • like #include <stdio.h>
    • It means that use the content in the stdio.h to replace the #
• About const
  • the value that is named const can not be modified
  • and it would be better to use const than define to define some const value.

• About passing the value

  • in C programming language
    • all the array is passed using reference(if the value change in the function, it will change.)
    • and all the value and const value are passed using value(if the value change in the function, it will not change.)

• About string I/O

  • gets
    • it is used to read a line in the content and store it as a parameter to pass to the array
    • the input line contains: a string and a newline
  • puts

• About *
  • the pointer point the address of a value that is stored in the memory

data type

• In C programming language, there are only 4 basic data type
  • int, float, pointer and polymerization
• INT
  • contains : char, short, int and long int
  • signed and ubsigned
  • thr range of the variable

  type	range
  char	0~127
  signed char	-127~127
  unsigned char	0~255
  short int	-32767~32767
  unsigned short int	0~65535
  int	-32767~32767
  unsigned int	0~65535
  long int	-2147483647~2147483647
  unsigned long int	0~4294967295

  • short int is at least 16 bits
  • long int is at least 32 bits
  • if the computer is 32 bits then int is 32 bits
    • else if the computer is 64 bits than the int is 32 bits
  • The range difference in difference kinds of machine

  data type	32 bits compiler	64 bits compiler
  char	1 byte	1 byte
  char *	4 bytes	8bytes
  short int	2 bytes	2 bytes
  int	4 bytes	4 bytes
  unsigned int	4 bytes	4 bytes
  float	4 bytes	4 bytes
  double	8 bytes	8 bytes
  long	4 bytes	4 bytes
  long long	8 bytes	8 bytes
  unsigned long	4 bytes	8 bytes

  • use sizeof(data type) to get the length of the data type
  • add 0 before number to make it octal number
  • add 0x before number to make it hexadecimal number
  • add L before character to make it wider charactor literal(it the environment support)
    • e.g L'X'
• FLOAT
  • contains : float, double, long double
  • range : 10^-37 ~ 10³⁷
  • in