To add to what they others have said: you are a beginner - do not use
#define _CRT_SECURE_NO_WARNINGS
as this tells the compiler to ignore things it thinks you are doing that might give you a problem.
In fact, you should use the appropriate compiler option to "treat all warnings as errors" so your code will not compile at all if the compiler is unsure you know what you are doing, and set the "warning level" to it's highest setting.
Trust me, as a beginner the compiler does know better than you - and you really shouldn't be telling it to ignore anything!
If nothing else, it should mean that your code will not run at all with either of these common beginner problems in it:
if (a = 666)
{
...
if (a == 666);
{
...
Both of which are pretty difficult to spot when in a large lump of code - because most people tend to read what they meant to write, rather than what they did!
But the big question is: why on Earth is a beginner learning C? It's a very, very old language now, and isn't used that much at all. I would expect new programmers to be learning much newer, more friendly languages like C# which don't have the many, many problems that C can frustratingly lead you into.