Scope of variables

All the variables that we intend to use in a program must have been declared with its type specifier in an earlier
point in the code, like we did in the previous code at the beginning of the body of the function main when we
declared that a, b, and result were of type int.
A variable can be either of global or local scope. A global variable is a variable declared in the main body of the
source code, outside all functions, while a local variable is one declared within the body of a function or a block. 

Global variables can be referred from anywhere in the code, even inside functions, whenever it is after its
declaration. The scope of local variables is limited to the block enclosed in braces ({}) where they are declared. For example,

if they are declared at the beginning of the body of a function (like in function main) their scope is between its
declaration point and the end of that function. In the example above, this means that if another function existed in
addition to main, the local variables declared in main could not be accessed from the other function and vice versa.