Mystery of "sprintf"

sprintf_E.c

#include <stdio.h>

void main(void) {
    int i;
    double x;
    char buff[256];

    x = 1.15;
    sprintf(buff, "1. sprintf(%f) => %.1E", x, x);
    puts(buff);

    x = 5 * 0.01 + 1.1;
    sprintf(buff, "2. sprintf(%f) => %.1E", x, x);
    puts(buff);
}

/*
Results:
    1. sprintf(1.150000) => 1.1E+00
    2. sprintf(1.150000) => 1.2E+00
*/