C语言：%5.2f 含义

#include <stdio.h>
main()
{
    float a=-3.14153265;
    printf("%8.4f\n",a) ;
    printf("%7.4f\n",a) ;
    printf("%6.4f\n",a) ;
    printf("%5.4f\n",a) ;
    printf("%4.4f\n",a) ;
    printf("%3.4f\n",a) ;
    printf("%2.4f\n",a) ;
    printf("%1.4f\n",a) ;
    printf("%0.4f\n",a) ;
    a=+3.14153265;
    printf("\n%8.4f\n",a) ;
    printf("%7.4f\n",a) ;
    printf("%6.4f\n",a) ;
    printf("%5.4f\n",a) ;
    printf("%4.4f\n",a) ;
    printf("%3.4f\n",a) ;
    printf("%2.4f\n",a) ;
    printf("%1.4f\n",a) ;
    printf("%0.4f\n",a) ;
    int b=12;
    printf("\n%2d\n",b);
    printf("%3d\n",b);
    printf("%4d\n",b);
    printf("%5d\n",b);
    b=-12;
    printf("\n%2d\n",b);
    printf("%3d\n",b);
    printf("%4d\n",b);
    printf("%5d\n",b);
    


    getchar();
 }