While concatenating C with A the result is not what I wanted. How can I get hellojames instead of helloworldjames?
char A[12] = "hello";
char B[12] = "world";
char C[12] = "james";
strcat(A,B);
printf("%s", A);
output = helloworld
strcat(A,C);
printf("%s",A);
output = helloworldjames
When you use strcat(A, B), the null char ('\0') marking the end of the A string gets replaced by the first char in B and all the following chars in B get appended from this point onward to A (that must be large enough to hold the result of the concatenation or undefined behaviour could occur).
After the strcat() call, A is no longer what you initially defined it to be, but a new string resulting from the concatenation.
If you want to reverse this, a simple solution is to keep A's lenght before doing the concatenation using strlen():
int A_len = strlen(A);
This way to reverse strcat(A, B) you only need to set the null char where it used to be before the concatenation:
A[A_len] = '\0';
After this replacement, strcat(A, C) returns hellojames.
When you do the strcat(A,B), you are modifying the string A points to. You need to create a working buffer. Something like:
char work[12];
strcpy(work, A);
strcat(work, B);
printf("%s", work);
strcpy(work, A);
strcat(work, C);
printf("%s", work);
