Main Function
The main function is a special function. Every C++ program must contain a function named main. It serves as the entry point for the program. The computer will start running the code from the beginning of the main function.
Types of Main Functions
1. Without parameters:
CPP
// Without Parameters int main() { ... return 0; } |
2. With parameters:
CPP
// With Parameters int main( int argc, char * const argv[]) { ... return 0; } |
The reason for having the parameter option for the main function is to allow input from the command line. When you use the main function with parameters, it saves every group of characters (separated by a space) after the program name as elements in an array named argv.
Since the main function has the return type of int, the programmer must always have a return statement in the code. The number that is returned is used to inform the calling program what the result of the program’s execution was. Returning 0 signals that there were no problems.
Functions in C++
A function is a set of statements that takes input, does some specific computation, and produces output. The idea is to put some commonly or repeatedly done tasks together to make a function so that instead of writing the same code again and again for different inputs, we can call this function.
In simple terms, a function is a block of code that runs only when it is called.
Syntax:
Example:
C++
// C++ Program to demonstrate working of a function #include <iostream> using namespace std; // Following function that takes two parameters 'x' and 'y' // as input and returns max of two input numbers int max( int x, int y) { if (x > y) return x; else return y; } // main function that doesn't receive any parameter and // returns integer int main() { int a = 10, b = 20; // Calling above function to find max of 'a' and 'b' int m = max(a, b); cout << "m is " << m; return 0; } |
m is 20
Time complexity: O(1)
Space complexity: O(1)