If a program is large, it is subdivided into a number of smaller
programs that are called modules or subprograms. If a complex
problem is solved using more modules, this approach is known as
modular programming

Global , static, local :  In main memory          
Register variable: In registers
C program : In main memory.

An argument is an entity used to pass the data from calling function to
the called function. Formal arguments are the arguments available in
the function definition. They are preceded by their own data types.
Actual arguments are available in the function call.

A switch statement is generally best to use when you have more than two conditional expressions based on a single variable of numeric type.

A linker converts an object code into an executable code by linking together the necessary build in functions. The form and place of declaration where the variable is declared in a program determine the
linkage of variable.