Input and output of scanf and printf (format controller)

One 、 Use scanf Input and printf Output

These two functions are C In language

1、scanf Use

Format ：

scanf(" Format control ", Variable address );
scanf("%d",&n);

Of common data type variables scanf Format symbol

int	%d
long long	%lld
float	%f
char	%c
double	%lf
character string (char Array )	%s

image 13:45:20 You can type it like this

scanf("%d:%d:%d",&h,&m,&s);

except %c Outside ,scanf The input of other format characters is with the blank character （ Space 、Tab） Is the end judgment flag , The character array uses %s When reading in, use space and line feed as the sign of the end of reading ,%c You can read spaces and line breaks .

2、printf Use

printf(" Format control ", Variable name );

The format controller has only double Turn into %f
If you want to output % , Just add one in front % \

Two 、 Common output formats

1、%md

Can make insufficient m Bit int Type variable With m Bit right aligned output , Fill in the high order with blank space , If itself exceeds m Bits remain the same .

#include<iostream>
using namespace std;
int main()
{
      
    int a=123,b=123456;
    printf("%5d\n",a);
    printf("%5d\n",b);
    return 0;
}

  123
123456

2、%0md

And %md The difference is , When the variable is insufficient m When a , Make up 0.

#include<iostream>
using namespace std;
int main()
{
      
    int a=123,b=123456;
    printf("%5d\n",a);
    printf("%5d\n",b);
    printf("%05d\n",a);
    return 0;
}

  123
123456
00123

3、%.mf

You can keep floating point numbers m Decimal output

#include<iostream>
using namespace std;
int main()
{
      
    double d=3.14159;
    printf("%.0f\n",d);
    printf("%.1f\n",d);
    printf("%.2f",d);
    return 0;
}

3
3.1
3.14

3、 ... and 、 Use getchar Input 、putchar Output single character

Can recognize line breaks

char c1,c2;
c1=getchar();
c2=getchar();
putchar(c1);
putchar(c2);