Both C and C++ (as well as many of the more recent languages derived from them) distinguish between a constant containing a single character and a constant containing a string of characters. The way you quote the content does count.
The Difference Between Characters and Strings

One topic I haven’t added to in quite a while is the one on C++ programming. In this article I discuss how to start up a second program from within a C++ program. There are two ways of doing this depending on how you want the two programs to interact.
Using EXEC and SPAWN to Link [...]