Error message:
Arduino: 1.8.5 (Windows 10), Board: "Arduino/Genuino Uno"
C:\Program Files (x86)\Arduino\arduino-builder -dump-prefs -logger=machine -hardware C:\Program Files (x86)\Arduino\hardware -tools C:\Program Files (x86)\Arduino\tools-builder -tools C:\Program Files (x86)\Arduino\hardware\tools\avr -built-in-libraries C:\Program Files (x86)\Arduino\libraries -libraries C:\Users\collw\OneDrive\Documents\Arduino\libraries -fqbn=arduino:avr:uno -vid-pid=0X2341_0X0043 -ide-version=10805 -build-path C:\Users\collw\AppData\Local\Temp\arduino_build_848542 -warnings=none -build-cache C:\Users\collw\AppData\Local\Temp\arduino_cache_196978 -prefs=build.warn_data_percentage=75 -prefs=runtime.tools.arduinoOTA.path=C:\Program Files (x86)\Arduino\hardware\tools\avr -prefs=runtime.tools.avr-gcc.path=C:\Program Files (x86)\Arduino\hardware\tools\avr -prefs=runtime.tools.avrdude.path=C:\Program Files (x86)\Arduino\hardware\tools\avr -verbose E:\English\code\Lesson 20 Four Digital Seven Segment Display\Four_Digital\Four_Digital.ino
C:\Program Files (x86)\Arduino\arduino-builder -compile -logger=machine -hardware C:\Program Files (x86)\Arduino\hardware -tools C:\Program Files (x86)\Arduino\tools-builder -tools C:\Program Files (x86)\Arduino\hardware\tools\avr -built-in-libraries C:\Program Files (x86)\Arduino\libraries -libraries C:\Users\collw\OneDrive\Documents\Arduino\libraries -fqbn=arduino:avr:uno -vid-pid=0X2341_0X0043 -ide-version=10805 -build-path C:\Users\collw\AppData\Local\Temp\arduino_build_848542 -warnings=none -build-cache C:\Users\collw\AppData\Local\Temp\arduino_cache_196978 -prefs=build.warn_data_percentage=75 -prefs=runtime.tools.arduinoOTA.path=C:\Program Files (x86)\Arduino\hardware\tools\avr -prefs=runtime.tools.avr-gcc.path=C:\Program Files (x86)\Arduino\hardware\tools\avr -prefs=runtime.tools.avrdude.path=C:\Program Files (x86)\Arduino\hardware\tools\avr -verbose E:\English\code\Lesson 20 Four Digital Seven Segment Display\Four_Digital\Four_Digital.ino
Using board 'uno' from platform in folder: C:\Program Files (x86)\Arduino\hardware\arduino\avr
Using core 'arduino' from platform in folder: C:\Program Files (x86)\Arduino\hardware\arduino\avr
Detecting libraries used...
"C:\Program Files (x86)\Arduino\hardware\tools\avr/bin/avr-g++" -c -g -Os -w -std=gnu++11 -fpermissive -fno-exceptions -ffunction-sections -fdata-sections -fno-threadsafe-statics -flto -w -x c++ -E -CC -mmcu=atmega328p -DF_CPU=16000000L -DARDUINO=10805 -DARDUINO_AVR_UNO -DARDUINO_ARCH_AVR "-IC:\Program Files (x86)\Arduino\hardware\arduino\avr\cores\arduino" "-IC:\Program Files (x86)\Arduino\hardware\arduino\avr\variants\standard" "C:\Users\collw\AppData\Local\Temp\arduino_build_848542\sketch\Four_Digital.ino.cpp" -o "nul"
Generating function prototypes...
"C:\Program Files (x86)\Arduino\hardware\tools\avr/bin/avr-g++" -c -g -Os -w -std=gnu++11 -fpermissive -fno-exceptions -ffunction-sections -fdata-sections -fno-threadsafe-statics -flto -w -x c++ -E -CC -mmcu=atmega328p -DF_CPU=16000000L -DARDUINO=10805 -DARDUINO_AVR_UNO -DARDUINO_ARCH_AVR "-IC:\Program Files (x86)\Arduino\hardware\arduino\avr\cores\arduino" "-IC:\Program Files (x86)\Arduino\hardware\arduino\avr\variants\standard" "C:\Users\collw\AppData\Local\Temp\arduino_build_848542\sketch\Four_Digital.ino.cpp" -o "C:\Users\collw\AppData\Local\Temp\arduino_build_848542\preproc\ctags_target_for_gcc_minus_e.cpp"
"C:\Program Files (x86)\Arduino\tools-builder\ctags\5.8-arduino11/ctags" -u --language-force=c++ -f - --c++-kinds=svpf --fields=KSTtzns --line-directives "C:\Users\collw\AppData\Local\Temp\arduino_build_848542\preproc\ctags_target_for_gcc_minus_e.cpp"
Compiling sketch...
"C:\Program Files (x86)\Arduino\hardware\tools\avr/bin/avr-g++" -c -g -Os -w -std=gnu++11 -fpermissive -fno-exceptions -ffunction-sections -fdata-sections -fno-threadsafe-statics -MMD -flto -mmcu=atmega328p -DF_CPU=16000000L -DARDUINO=10805 -DARDUINO_AVR_UNO -DARDUINO_ARCH_AVR "-IC:\Program Files (x86)\Arduino\hardware\arduino\avr\cores\arduino" "-IC:\Program Files (x86)\Arduino\hardware\arduino\avr\variants\standard" "C:\Users\collw\AppData\Local\Temp\arduino_build_848542\sketch\Four_Digital.ino.cpp" -o "C:\Users\collw\AppData\Local\Temp\arduino_build_848542\sketch\Four_Digital.ino.cpp.o"
Compiling libraries...
Compiling core...
Using previously compiled file: C:\Users\collw\AppData\Local\Temp\arduino_build_848542\core\wiring_pulse.S.o
Using previously compiled file: C:\Users\collw\AppData\Local\Temp\arduino_build_848542\core\WInterrupts.c.o
Using previously compiled file: C:\Users\collw\AppData\Local\Temp\arduino_build_848542\core\hooks.c.o
Using previously compiled file: C:\Users\collw\AppData\Local\Temp\arduino_build_848542\core\wiring.c.o
Using previously compiled file: C:\Users\collw\AppData\Local\Temp\arduino_build_848542\core\wiring_analog.c.o
Using previously compiled file: C:\Users\collw\AppData\Local\Temp\arduino_build_848542\core\wiring_digital.c.o
Using previously compiled file: C:\Users\collw\AppData\Local\Temp\arduino_build_848542\core\wiring_pulse.c.o
Using previously compiled file: C:\Users\collw\AppData\Local\Temp\arduino_build_848542\core\wiring_shift.c.o
Using previously compiled file: C:\Users\collw\AppData\Local\Temp\arduino_build_848542\core\CDC.cpp.o
Using previously compiled file: C:\Users\collw\AppData\Local\Temp\arduino_build_848542\core\HardwareSerial.cpp.o
Using previously compiled file: C:\Users\collw\AppData\Local\Temp\arduino_build_848542\core\HardwareSerial0.cpp.o
Using previously compiled file: C:\Users\collw\AppData\Local\Temp\arduino_build_848542\core\HardwareSerial1.cpp.o
Using previously compiled file: C:\Users\collw\AppData\Local\Temp\arduino_build_848542\core\HardwareSerial2.cpp.o
Using previously compiled file: C:\Users\collw\AppData\Local\Temp\arduino_build_848542\core\HardwareSerial3.cpp.o
Using previously compiled file: C:\Users\collw\AppData\Local\Temp\arduino_build_848542\core\IPAddress.cpp.o
Using previously compiled file: C:\Users\collw\AppData\Local\Temp\arduino_build_848542\core\PluggableUSB.cpp.o
Using previously compiled file: C:\Users\collw\AppData\Local\Temp\arduino_build_848542\core\Print.cpp.o
Using previously compiled file: C:\Users\collw\AppData\Local\Temp\arduino_build_848542\core\Stream.cpp.o
Using previously compiled file: C:\Users\collw\AppData\Local\Temp\arduino_build_848542\core\Tone.cpp.o
Using previously compiled file: C:\Users\collw\AppData\Local\Temp\arduino_build_848542\core\USBCore.cpp.o
Using previously compiled file: C:\Users\collw\AppData\Local\Temp\arduino_build_848542\core\WMath.cpp.o
Using previously compiled file: C:\Users\collw\AppData\Local\Temp\arduino_build_848542\core\WString.cpp.o
Using previously compiled file: C:\Users\collw\AppData\Local\Temp\arduino_build_848542\core\abi.cpp.o
Using previously compiled file: C:\Users\collw\AppData\Local\Temp\arduino_build_848542\core\main.cpp.o
Using previously compiled file: C:\Users\collw\AppData\Local\Temp\arduino_build_848542\core\new.cpp.o
Using previously compiled file: C:\Users\collw\AppData\Local\Temp\arduino_build_848542\core\core.a
Archiving built core (caching) in: C:\Users\collw\AppData\Local\Temp\arduino_cache_196978\core\core_arduino_avr_uno_0c812875ac70eb4a9b385d8fb077f54c.a
Linking everything together...
"C:\Program Files (x86)\Arduino\hardware\tools\avr/bin/avr-gcc" -w -Os -g -flto -fuse-linker-plugin -Wl,--gc-sections -mmcu=atmega328p -o "C:\Users\collw\AppData\Local\Temp\arduino_build_848542/Four_Digital.ino.elf" "C:\Users\collw\AppData\Local\Temp\arduino_build_848542\sketch\Four_Digital.ino.cpp.o" "C:\Users\collw\AppData\Local\Temp\arduino_build_848542/core\core.a" "-LC:\Users\collw\AppData\Local\Temp\arduino_build_848542" -lm
c:/program files (x86)/arduino/hardware/tools/avr/bin/../lib/gcc/avr/4.9.2/../../../../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/Genuino Uno.