Arduino Uploading error

Hi all

i have been working on a project and suddenly while trying to upload some code to my arduino uno i started getting this error.

Arduino: 1.8.1 (Windows 10), Board: "Arduino/Genuino Uno"

c:\program files (x86)\arduino\hardware\tools\avr\bin../lib/gcc/avr/4.9.2/../../../../avr/bin/ar.exe: unable to rename 'core\core.a'; reason: File exists

exit status 1 Error compiling for board Arduino/Genuino Uno. Sketch uses 4802 bytes (14%) of program storage space. Maximum is 32256 bytes. Global variables use 337 bytes (16%) of dynamic memory, leaving 1711 bytes for local variables. Maximum is 2048 bytes. avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0xff avrdude: stk500_getsync() attempt 2 of 10: not in sync: resp=0x00 avrdude: stk500_getsync() attempt 3 of 10: not in sync: resp=0x00 avrdude: stk500_getsync() attempt 4 of 10: not in sync: resp=0x00 avrdude: stk500_getsync() attempt 5 of 10: not in sync: resp=0x00 avrdude: stk500_getsync() attempt 6 of 10: not in sync: resp=0x00 avrdude: stk500_getsync() attempt 7 of 10: not in sync: resp=0x00 avrdude: stk500_getsync() attempt 8 of 10: not in sync: resp=0x81 avrdude: stk500_getsync() attempt 9 of 10: not in sync: resp=0x24 avrdude: stk500_getsync() attempt 10 of 10: not in sync: resp=0x40 An error occurred while uploading the sketch

can anyone explain what is going on here and how i might fix it

regards samuel

Shut down the IDE and restart it. Check that the COM port needed exists and is selected, similarly with the board type. Reboot the PC if necessary.