Issue with Uploading Code on Arduino UNO R3

Hey all,

I've been programming and switching boards, but am now having trouble running a simple program (ex. blink, serial monitor) on the Arduino. This is the error that I'm getting.

c:/program files (x86)/arduino/hardware/tools/avr/bin/../lib/gcc/avr/7.3.0/../../../../avr/lib/avr5/crtatmega328p.o:(.init9+0x0): undefined reference to `main'

collect2.exe: error: ld returned 1 exit status

exit status 1
Error compiling for board Arduino Uno.

This report would have more information with
"Show verbose output during compilation"

Any help would be greatly appreciated. Thanks!
Ishan Saha