String type in arduino ide is not wroking!

HiFive1 Rev B
11

These are the tests that i have done in the morning in different systems.

I)Windows10(currently i am using)
Arduino version 1.8.9
output:

String charAt() and setCharAt():

II)Linux(ubuntu 18.04)
Arduino Version 1.8.8
output:

        String charAt() and setCharAt():
        SensorReading: 456
        Most significant digit of the sensor reading is: 4
        SensorReading= 456

III)Windows7 (colleague’s system)
Arduino Version 1.8.8
output:

String charAt() and setCharAt():

I guess, if i reinstall the ide in my system again , the same issue will occur.,