Absolutely. Indeed, any function (user-defined or built-in) that does not return a value is not really a function, it is simply a procedure.
No the two work together REALLY
Default functions are pre defined functions.Eg. printf();scanf();getch();clrscr();etc..Actually, no-one uses the term 'default function'. (Let alone 'defult function'.)Another answer: Perhaps it is 'main' what you meant.
Not possible.
If the function has been declared and defined, then the only remaining issue is scope, i.e. visibility.
No. Functions should be defined separately. So you would not define a function within a function. You can define one function, and while defining another function, you can call the first function from its code.
There are no 'sections' in C source, you can define functions anywhere, except inside another function or variable/type definition.
A function statement is a block where the function is declared and defined.
Yes, if the function is equal to zero at x=0, the function is considered defined at that point. The function's value at x=0 does not impact its overall definition.
You cannot because the function is not well-defined. There is no equality symbol, the function In(2x) is not defined.
A piecewise defined function is a function which is defined symbolically using two or more formulas
That depends on how the function is defined.
A function statement is a block where the function is declared and defined.
The set of all values of x, for which the equation is true is the domain of the function defined by that equation.
Absolutely. Indeed, any function (user-defined or built-in) that does not return a value is not really a function, it is simply a procedure.
You can write them any way you like, as long as the basic definition of "function" is maintained. Basically, this means that the function must be defined uniquely defined for every input.
No the two work together REALLY