Functions in C++

Functions in C++

A function is a group of statements that together perform a task. Every C++ program has at least one function, which is main(), and all the most trivial programs can define additional functions.

You can divide up your code into separate functions. How you divide up your code among different functions is up to you, but logically the division usually is such that each function performs a specific task.

A function declaration tells the compiler about a function's name, return type, and parameters. A function definition provides the actual body of the function.

The C++ standard library provides numerous built-in functions that your program can call. For example, function strcat() to concatenate two strings, function memcpy() to copy one memory location to another location and many more functions.

A function is known with various names like a method or a sub-routine or a procedure etc.

Defining a Function

A C++ function definition consists of a function header and a function body. Here are all the parts of a function −

·        Return Type − A function may return a value. The return_type is the data type of the value the function returns. Some functions perform the desired operations without returning a value. In this case, the return_type is the keyword void.

·        Function Name − This is the actual name of the function. The function name and the parameter list together constitute the function signature.

·        Parameters − A parameter is like a placeholder. When a function is invoked, you pass a value to the parameter. This value is referred to as actual parameter or argument. The parameter list refers to the type, order, and number of the parameters of a function. Parameters are optional; that is, a function may contain no parameters.

·        Function Body − The function body contains a collection of statements that define what the function does.

Calling a Function

While creating a C++ function, you give a definition of what the function has to do. To use a function, you will have to call or invoke that function.

When a program calls a function, program control is transferred to the called function. A called function performs defined task and when it’s return statement is executed or when its function-ending closing brace is reached, it returns program control back to the main program.

To call a function, you simply need to pass the required parameters along with function name, and if function returns a value, then you can store returned value.

Program input:

#include <iostream>

using namespace std;

// function declaration

int max(int num1, int num2);

int main () {

   // local variable declaration:

   int a = 100;

   int b = 200;

   int ret;

   // calling a function to get max value.

   ret = max(a, b);

   cout << "Max value is : " << ret << endl;

   return 0;

}

// function returning the max between two numbers

int max(int num1, int num2) {

   // local variable declaration

   int result;

   if (num1 > num2)

      result = num1;

   else

      result = num2;

   return result;

}

Program Output:

Max value is : 200

Function Arguments

If a function is to use arguments, it must declare variables that accept the values of the arguments. These variables are called the formal parametersof the function.

The formal parameters behave like other local variables inside the function and are created upon entry into the function and destroyed upon exit.

While calling a function, there are two ways that arguments can be passed to a function −

Sr.No	Call Type & Description
1	Call by Value This method copies the actual value of an argument into the formal parameter of the function. In this case, changes made to the parameter inside the function have no effect on the argument.
2	Call by Pointer This method copies the address of an argument into the formal parameter. Inside the function, the address is used to access the actual argument used in the call. This means that changes made to the parameter affect the argument.
3	Call by Reference This method copies the reference of an argument into the formal parameter. Inside the function, the reference is used to access the actual argument used in the call. This means that changes made to the parameter affect the argument.

By default, C++ uses call by value to pass arguments. In general, this means that code within a function cannot alter the arguments used to call the function and above mentioned example while calling max() function used the same method.

C++ Basic Input/Output

C++ Basic Input/Output

Definition

The C++ standard libraries provide an extensive set of input/output capabilities which we will see in subsequent chapters. This chapter will discuss very basic and most common I/O operations required for C++ programming.

C++ I/O occurs in streams, which are sequences of bytes. If bytes flow from a device like a keyboard, a disk drive, or a network connection etc. to main memory, this is called input operation and if bytes flow from main memory to a device like a display screen, a printer, a disk drive, or a network connection, etc., this is called output operation.

I/O Library Header Files

There are following header files important to C++ programs −

Sr.No	Header File & Function and Description
1	<iostream> This file defines the cin, cout, cerr and clog objects, which correspond to the standard input stream, the standard output stream, the un-buffered standard error stream and the buffered standard error stream, respectively.
2	<iomanip> This file declares services useful for performing formatted I/O with so-called parameterized stream manipulators, such as setw and setprecision.
3	<fstream> This file declares services for user-controlled file processing. We will discuss about it in detail in File and Stream related chapter.

The Standard Output Stream (cout)

The predefined object cout is an instance of ostream class. The cout object is said to be "connected to" the standard output device, which usually is the display screen. The cout is used in conjunction with the stream insertion operator,

Input:-

#include <iostream>

using namespace std;

 int main() {

   char name[50];

   cout << "Please enter your name: ";

   cin >> name;

   cout << "Your name is: " << name << endl;

}

 OutPut:-

Please enter your name: M.Asif Saeed

Your name is: M.Asif Saeed

Math Operators Program

Math Operators Program

Input:

#include <cmath>

using namespace std;

int main () {

   // number definition:

   short  s = 10;

   int    i = -1000;

   long   l = 100000;

   float  f = 230.47;

   double d = 200.374;

   // mathematical operations;

   cout << "sin(d) :" << sin(d) << endl;

   cout << "abs(i)  :" << abs(i) << endl;

   cout << "floor(d) :" << floor(d) << endl;

   cout << "sqrt(f) :" << sqrt(f) << endl;

   cout << "pow( d, 2) :" << pow(d, 2) << endl;

   return 0;

}

Output:

Numbers In C++

Numbers In C++

We use primitive data types such as int, short, long, float and double, etc. The number data types, their possible values and number ranges have been explained while discussing C++ Data Types.

Input:

#include <iostream>

using namespace std;

int main () {

   // number definition:

   short  s;

   int    i;

   long   l;

   float  f;

   double d;

  

   // number assignments;

   s = 10;     

   i = 1000;   

   l = 1000000;

   f = 230.47; 

   d = 30949.374;

  

   // number printing;

   cout << "short  s :" << s << endl;

   cout << "int    i :" << i << endl;

   cout << "long   l :" << l << endl;

   cout << "float  f :" << f << endl;

   cout << "double d :" << d << endl;

   return 0;

}

 Output:-

Random Number in C++

Random Number in C++

Definition:-

There are many cases where you will wish to generate a random number. There are actually two functions you will need to know about random number generation. The first is rand(), this function will only return a pseudo random number. The way to fix this is to first call the srand() function.

Following is a simple example to generate few random numbers. This example makes use of time() function to get the number of seconds on your system time, to randomly seed the rand() function –

Program:-

Input:-

#include <iostream>

#include <ctime>

#include <cstdlib>

using namespace std;

int main () {

   int i,j;

   // set the seed

   srand( (unsigned)time( NULL ) );

   /* generate 10  random numbers. */

   for( i = 0; i < 10; i++ ) {

      // generate actual random number

      j = rand();

      cout <<" Random Number : " << j << endl;

   }

   return 0;

}

Output:-

Output 2:

Adding Integer Program in C++

                        Adding Integer Program in C++

                                                     Program Input:-

#include <iostream>

#include <ctime>

#include <cstdlib>

using namespace std;

int main () { // Start Main Function

  

       int Number1; // First Integer to Add

       int Number2; // Secong Integer to Add

       int Sum; // Add Sum of Integer one And Number two

       cout << " Enter First Number" << endl;

       cin >> Number1;

       cout << "Enter Second Numbre"<<endl;

       cin >> Number2;

       Sum = Number1 + Number2;  // Add the number And store sum

       cout << "Sum is " << Sum << endl;

               

} // End Main Function

OutPut:-

Math Operations in C++

Definition:-

In addition to the various functions you can create, C++ also includes some useful functions you can use. These functions are available in standard C and C++ libraries and called built-in functions. These are functions that can be included in your program and then use.

C++ has a rich set of mathematical operations, which can be performed on various numbers. Following table lists down some useful built-in mathematical functions available in C++.

Operations:

Sr.No	Function & Purpose
1	double cos(double); This function takes an angle (as a double) and returns the cosine.
2	double sin(double); This function takes an angle (as a double) and returns the sine.
3	double tan(double); This function takes an angle (as a double) and returns the tangent.
4	double log(double); This function takes a number and returns the natural log of that number.
5	double pow(double, double); The first is a number you wish to raise and the second is the power you wish to raise it t
6	double hypot(double, double); If you pass this function the length of two sides of a right triangle, it will return you the length of the hypotenuse.
7	double sqrt(double); You pass this function a number and it gives you the square root.
8	int abs(int); This function returns the absolute value of an integer that is passed to it.
9	double fabs(double); This function returns the absolute value of any decimal number passed to it.
10	double floor(double); Finds the integer which is less than or equal to the argument passed to it.