Why function 'printf' of <stdio.h> did not work?

When I test some cases in the function ‘app_main()’, the strings didn’t come out automatically. I have open all types of terminals but find nothing I want. Here is the code:

#include <stdio.h>
void app_main()
printf(“Hello World\n”);
while (getchar() != 10)

So, which terminal can help print the strings? I have tried ‘PROBLEMS’, ‘OUTPUT’, ‘DEBUG CONSOLE’, ‘TERMINAL’ in Vscode and ‘Upload’, ‘PlatformIO CLI’, ‘Build’ in Platformio Extension.

The Upload + Monitor project task.

Remember to set monitor_speed correctly, 115200 by default for ESP-IDF.