It is a null character, used to signal the end of a string. Essentially, when a program is reading a string, it needs to know how long the string is so it knows when to stop interpreting the information as such. There are a couple ways to do this. Either you can create an attribute that says the number of characters to expect before starting to read the string or you can signal the end of the string when it happens. Most programming languages today use the null character because then the program simply runs until it finds the first null byte after the start of a string to know the string is finished. This has the added advantages of requiring only one byte of information to identify the end of the string and the string can be any length.If you were to do it the other way, the program would have to allocate resources to tell the program how long the string is going to be. If you only use 1 byte, then the string only has a max length of 255. Any more than that requires more memory and is less efficient. This also could lead to overflows which can cause problems in execution if a string is longer than the string length counter can communicate.
