Modify string constants in C/C ++

Run the following code in (and only in tc2.0). Do not check the result first. Think about what you will get:
# Include <stdio. h>
# Include <stdlib. h>

Int
Main (INT argn, char * argv [])
{
Char * szstringa = "Hello, world! ";
Char * szstringb = "Hello, world! ";

* Szstringa = '-';
Puts (szstringb );

Return 0;
}
The output result is: "-ello, world! ";. Is it different from what you think?
Ansi c clearly states that the effect of modifying a String constant is undefined.
First, we need to know how to obtain the String constant? There is only one way: char * szstring = "Hello, world !"; This declaration produces a String constant. Char szstring [] = "Hello, world !"; Yes? No! The result is a string variable. Now, because ansi c does not require the compiler implementer to process string constants, Some compilers will regard the same multiple string constants as one (note: this optimization is only possible in string constants. Do not use generic constants of other types. For example: int num1 = 11; int num2 = 11; although it is two identical constants, modifying num1 does not affect num2). The purpose is to save memory space, when the string a is modified, B is also modified. It can be seen from this that tc2.0 has optimized the string constants, while other compilers (such as devc ++ 5.0) may not be optimized, and the result may not be compiled, or through compilation, but the result is a garbage value. Due to these uncertainties, we should avoid modifying string constants as much as possible.
What if you have to modify the string? Yes! Yes! Note: We want to modify the character. Therefore, you only need to define string variables instead of string constants. As mentioned above, char szstring [] = "Hello, world!" can be defined as an array !";; In this way, you can modify the string in the program.
Try the following code:
# Include <stdio. h>
# Include <stdlib. h>

Int
Main (INT argn, char * argv [])
{
Char szstringa [] = "Hello, world! ";
Char szstringb [] = "Hello, world! ";

Szstringa [0] = '-';
Puts (szstringb );

Return 0;
}
No problem.
OK. Remember: to modify the string, use char szstring [] = "Hello, world !"; Proceed!