How to call function within function in C or C++ Last Updated : 29 Jul, 2024 Comments Improve Suggest changes Like Article Like Report When we begin programming in C/C++, we generally write one main() function and write all our logic inside this. This approach is fine for very small programs, but as the program size grows, this become unmanageable. So we use functions. We write code in the form of functions. The main function always acts as a driver function and calls other functions. C++ // C++ program to call a function in main #include <iostream> using namespace std; // Function called inside main int add(int num1, int num2) { return (num1 + num2); } // Driver code int main() { int num1 = 12, num2 = 34; cout << add(num1, num2); return 0; } C // C program to call a function in main #include <stdio.h> // Function called inside main int add(int num1, int num2) { return (num1 + num2); } // Driver code int main() { int num1 = 12, num2 = 34; printf("%d", add(num1, num2); return 0; } Output46 We can also write function call as a parameter to function. In the below code, first add(num1, num2) is evaluated, let the result of this be r1. The add(r1, num3) is evaluated. Let the result of this be r2. Finally add(r2, num4) is evaluated and its result is printed. CPP // C++ program to call a function in main #include <iostream> using namespace std; // Function to add two numbers int add(int num1, int num2) { return (num1 + num2); } // Driver code int main() { int num1 = 12, num2 = 34, num3 = 67, num4 = 12; // The innermost add() is computed first, then middle // add(), then the outermost add() cout << add(add(add(num1, num2), num3), num4); return 0; } C // C program to call a function in main #include <stdio.h> // Function to add two numbers int add(int num1, int num2) { return (num1 + num2); } // Driver code int main() { int num1 = 12, num2 = 34, num3 = 67, num4 = 12; // The innermost add() is computed first, then middle // add(), then the outermost add() printf("%d", add(add(add(num1, num2), num3), num4)); return 0; } Output125 Another example of function calling function are as follows : - CPP // C++ program to show how to call a function inside a // function #include <iostream> using namespace std; // funtion declartion int add(int num1, int num2); int sub(int num1, int num2); int mul(int num1, int num2); int calculator(int num1, int num2, int option) { // calling add function within calculator function if (option == 1) { return add(num1, num2); } // calling sub function within calculator function if (option == 2) { return sub(num1, num2); } // calling mul function within calculator function if (option == 3) { return mul(num1, num2); } } // function for adding two numbers int add(int num1, int num2) { return (num1 + num2); } // function for subtracting numbers int sub(int num1, int num2) { return (num1 - num2); } // function for multiplying two number int mul(int num1, int num2) { return (num1 * num2); } // driver code int main() { int num1 = 10, num2 = 5; // variable // giving options for different // calculation(add, sub, mul, div) int option; option = 1; // Assuming that user inputs 1 cout << calculator(num1, num2, option); return 0; } C // C program to show how to call a function inside a // function #include <stdio.h> // function declarations int add(int num1, int num2); int sub(int num1, int num2); int mul(int num1, int num2); int calculator(int num1, int num2, int option) { // calling add function within calculator function if (option == 1) { return add(num1, num2); } // calling sub function within calculator function if (option == 2) { return sub(num1, num2); } // calling mul function within calculator function if (option == 3) { return mul(num1, num2); } } // function for adding two numbers int add(int num1, int num2) { return (num1 + num2); } // function for subtracting numbers int sub(int num1, int num2) { return (num1 - num2); } // function for multiplying two numbers int mul(int num1, int num2) { return (num1 * num2); } // driver code int main() { int num1 = 10, num2 = 5; // variables // giving options for different // calculations (add, sub, mul, div) int option; option = 1; // Assuming that user inputs 1 printf("%d\n", calculator(num1, num2, option)); return 0; } Output15 Comment More infoAdvertise with us Next Article How to call function within function in C or C++ T tusharupadhyay Follow Improve Article Tags : C++ Programs C Language C++ CPP-Functions Practice Tags : CPP Similar Reads How to Create a Pointer to a Function in C++? 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