what is a ~ in c++

Array callback has to contain indices 0 and 1 in C:\xampp\htdocs\crud\update.php:15 Stack trace: #0 {main}

Fatal error: Uncaught Error: Call to undefined function mysqli_connect() in C:\Users\Joalu\Desktop\new.php:3 Stack trace: #0 {main}

Warning: mail(): Failed to connect to mailserver at "localhost" port 25, verify your "SMTP" and "smtp_port" setting in php.ini or use ini_set() in C:\xampp\htdocs\PPETrackerApp\email.php on line 21

Write a function called clean that takes a C++ string as input and removes any characters in the string that are not letters except for space blanks.

[ERROR] InvalidArgumentException: Wrong file in C:\xampp\htdocs\magento2.4\lib\internal\Magento\Framework\Image\Adapter\Gd2.php:64 Stack trace

write a c++ program that reads ten strings and store them in array of strings, sort them and finally print the sorted strings

in a c program if you call "fwritef("got here")", you will get a compileerror, but if you add the line "void fwritef(char *);", you won't. why?

Fatal error: Allowed memory size of 536870912 bytes exhausted (tried to allocate 119541600 bytes) in C:\xampp\htdocs\backup-vice.php on line 67

the ios deployment target 'iphoneos_deployment_target' is set to 8.0, but the range of supported deployment target versions is 9.0 to 14.4.99. (in target 'grpc-c++' from project 'pods')

in tk.Button(self.frame, text = text, command= lambda:self.new_window(number, _class)).grid(padx= 5, pady= 5, sticky= N + E + W + S) File "C:\Users\CSB\Desktop\python program\triple_window.py", line 50, in new_window