a task is to Calculate a + b.

Pseudo Code:

file = openfile("pathToFile");
file.readLine(); //Discard the first Line 
while(line=file.readLine())
{
    splitted = tokenize(line, " ");
    first = splitted[0];
    second = splitted[1];
    writeToConsole(first + second);
}

Now since everything is broken down into a few small steps,
all you've got to do is translate these steps to C++.

Cheers

Manfred

Being a bit controversial here, the problem is one of those problems that if you followed the pseudocode given above you'd end up with a solution that's not really idiomatic in C++, it'd look like a clumsily ported C# or Java solution.

So given the C++ I/O entity is a stream, the solution looks more like:

extract number of lines to read from the input stream
while( there are still lines to process )
    extract the first integer on the line
    extract the second integer on the line
    sum the integers
    insert the result onto the output stream

if any errors occurred
    clear the stream
    tell the user about the error
    give up

Now if you wrap this lot up into a function that take an std::ostream and an std::istream you'll actually get something you can unit test and will work with console IO as well as files and even string.

Cheers,

Ash