New array declaration

Store the string in code ROM:

char code str[21] ="This can be display.";
LcdDisp(str);

char *LcdDisp(char *StrSrc);

Store the string in code ROM:

char code str[21] ="This can be display.";
LcdDisp(str);

char *LcdDisp(char *StrSrc);

Sounds like you need to get a 'C' textbook!

"Store the string in code ROM"

That will give a fixed string that can't be changed at runtime.
Is that what you actually wanted?

Note that there is no need to specify the array size when it is initialised with a string at definition:

char code str[] ="This can be display.";

If your want to read and write in an array,u can declare the array in idata or data RAM,if external RAM is valid,xdata could be used

char idata/data/xdata str[21]="read and wirte here.";

"to store a 20-character string in a arrary,your will have to assign 21-character space for it."

But, as I said earlier, there is no need to explicitly specify the length (eg 21) in the definition - the compiler will do it automatically.

In fact, unless you have a specific reason to do so, it's usually best not to specify the size - then there's no risk of miscounting, or if someone changes the string without remembering to change the size...!

but, if the length of the string which you declared is twenty,you don't need to specify the length,but while it is less than 20, for example

char idata str[]="hello";

strcpy(str,"this a 20-char sting");

"you need to store a 20-length string later on"

that's why I said, "...unless you have a specific reason to do so..."

In that case, yes - you would need to explicitly state the length as 21 in the definition.

strcpy(str,"this a 20-char sting");