C language data type (ii)

Char type

1.char Variable Constants

char c; Define a char variable

c = ' A ' A ' a ' character constant

The essence of char is an integer, with only one byte-sized integer

2.printf Output Char

%c means to output a character instead of an integer

3. Do not look print char transfer character

\a Alarm

int Main () {    char'\a';    printf ("%c\n", c); // ring a sound    return 0 ;}

\b Backspace

\ nthe line break

\ r Enter

\ t tab

\ \ Slash

\ ' Single quotation mark

\ "Double quotation marks

\? Question mark

\ n is a newline, which means that the cursor is moved down one cell

　　\ is carriage return, indicating that the cursor is to the beginning of

\ r \ n indicates carriage return line

4 Char and Unsiged Char

char a = 0; Defines a signed

Unsiged Char defines an unsigned char

　　

-124

floating-point float double long double type

1. Floating-point constant variable

Float in a 32-bit system 4 bytes

Double on a 32-bit system 8 bytes

Floating point number is not efficient, avoid using floating point number

Floating-point numbers are paid to integers and only integers are retained

Rounding Direct plus 0.5 to integer

#include <stdio.h>int  main () {    int5;     5 2 ;
Double F = 4; Floating point numbers are not efficient, avoid using floating-point    printf ("%d"// integers cannot retain digits after the decimal point    return0;}

2.printf output Floating point number

.%f

Type Restrictions

Const represents a constant that cannot be changed

A volatile variable is one that may be changed outside of the CPU instructions.

 #include <stdio.h>int   main () { volatile  int  i = 100 ; //     Tell the editor not to optimize code i + = for this variable;     i = i + 5  ;  //  External device changed the value of i  i = i + 10  ;    I  = i + 30  ; printf (  " %d\n   "    , I);  return  0  ;}  

Register

This is a suggested directive, not a command-line directive.

Register int i = 100;//i not in memory, directly inside the register of the CPU

　　

string format output input

"" is the way the C language expresses the string

The essence of a string is the character

　

Putchar Print one character

Putchar (' A ')->asc yards

SCANF read the user input through the keyboard, put into the variable, remember the parameter must be the address of the variable (&)

#include <stdio.h>int  main () {    int a=0, b=0;    scanf ("%d", &a);    scanf ("%d", &b);    printf ("a+b=%d", A +b)    ; return 0 ;}

GetChar to get the user keyboard input characters

#include <stdio.h>int  main () {    char0;     = GetChar ();    printf ("%c", a);     return 0 ;}

C language data type (ii)