The strings in C all point to the first character of the string with a char pointer, and the end of the string is indicated by' \0'(ASCII code value is 0).

while (*p 1！ = ' \ 0 ')p 1++； //Indicates that p 1 The pointer will skip to the next character before reaching the end of the string.

After the above loop, the pointer p 1 must point to the end of the string.

then

while (*p2！ ='\0'){*p 1=*p2，p 1++； P2++/ This is where P2 is copied to p 1 from beginning to end. Since p 1 has pointed to the end of the string, it is equivalent to connecting the string.