C++: error: expected primary-expression

void add(int register, int& acc)
{
    acc += register;
}

main.cpp:124: error: expected primary-开发者_开发百科expression before ‘register’

wth is wrong right there?

"register" is a keyword in C++ (a hangover from C days, mostly)

register is a C++ keyword, rename this to something else. It's used to qualify variables as a hint to the compiler to optimize the variable's storage directly to a CPU register rather than RAM - see here.