c - strcat function how to use -

i pretty new in c language. trying use strcat, following example works:

  char s1[20] = "happy ";   char s2[15] = "world";   char s3[40] = "";   strcat(s3,s1);

although, wanted practise bit pointers have seen earlier, so:

char *s1 = "happy"; char *s2 = "world";  strcat(*s2,*s1);

produces argument of type "char" incompatible parameter of type "const char *. again, might easy, clarifying possible

in second example,

strcat(*s2,*s1);

has type mismatch problem, *s2 , *s1 of type char. if use:

strcat(s2,s1);

it still wrong, because s2 points string literal, can't modified.

Call