What is the meaning of plus plus in c?

Answer 1

++a (plus plus a) is pre-incrementing operator to a
a=10;
printf("%d",++a); /* it will print 11 as ++a increment first a by 1 then prints it */

printf("%d",a++); /*it will printf 10 as it is post _ increment operator , it prints the value a first then increment it by 1 */

Answer 2

a += b is short for a = a + b

Answer 3

The plus plus designation (++) is the increment operator. The meaning is that C++ is the next incremental version of C.