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Normally, when we work with Numbers, 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.

Defining Numbers in C++

You have already defined numbers in various examples given in previous chapters. Here is another consolidated example to define various types of numbers in C++ −

#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;
}

When the above code is compiled and executed, it produces the following result −

short  s :10
int    i :1000
long   l :1000000
float  f :230.47
double d :30949.4

Math Operations in C++

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++.

To utilize these functions you need to include the math header file <cmath>.

Following is a simple example to show few of the mathematical operations −

#include <iostream>
#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;
}

When the above code is compiled and executed, it produces the following result −

sign(d)     :-0.634939
abs(i)      :1000
floor(d)    :200
sqrt(f)     :15.1812
pow( d, 2 ) :40149.7

Random Numbers in C++

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 −

#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 &lt;&lt;" Random Number : " &lt;&lt; j &lt;&lt; endl;
   }

   return 0;
}

When the above code is compiled and executed, it produces the following result −

Random Number : 1748144778
Random Number : 630873888
Random Number : 2134540646
Random Number : 219404170
Random Number : 902129458
Random Number : 920445370
Random Number : 1319072661
Random Number : 257938873
Random Number : 1256201101
Random Number : 580322989

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

The general form of a C++ function definition is as follows −

return_type function_name( parameter list ) {
   body of the 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.

Example

Following is the source code for a function called max(). This function takes two parameters num1 and num2 and return the biggest of both −

// 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; 
}

Function Declarations

A function declaration tells the compiler about a function name and how to call the function. The actual body of the function can be defined separately.

A function declaration has the following parts −

return_type function_name( parameter list );

For the above defined function max(), following is the function declaration −

int max(int num1, int num2);

Parameter names are not important in function declaration only their type is required, so following is also valid declaration −

int max(int, int);

Function declaration is required when you define a function in one source file and you call that function in another file. In such case, you should declare the function at the top of the file calling the function.

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. For example −

#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; 
}

I kept max() function along with main() function and compiled the source code. While running final executable, it would produce the following result −

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 parameters of 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 −

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.

Default Values for Parameters

When you define a function, you can specify a default value for each of the last parameters. This value will be used if the corresponding argument is left blank when calling to the function.

This is done by using the assignment operator and assigning values for the arguments in the function definition. If a value for that parameter is not passed when the function is called, the default given value is used, but if a value is specified, this default value is ignored and the passed value is used instead. Consider the following example −

#include <iostream>
using namespace std;
 
int sum(int a, int b = 20) {
   int result;
   result = a + b;
  
   return (result);
}
int main () {
   // local variable declaration:
   int a = 100;
   int b = 200;
   int result;
 
   // calling a function to add the values.
   result = sum(a, b);
   cout << "Total value is :" << result << endl;

   // calling a function again as follows.
   result = sum(a);
   cout << "Total value is :" << result << endl;
 
   return 0;
}

When the above code is compiled and executed, it produces the following result −

Total value is :300
Total value is :120

Decision making structures require that the programmer specify one or more conditions to be evaluated or tested by the program, along with a statement or statements to be executed if the condition is determined to be true, and optionally, other statements to be executed if the condition is determined to be false.

Following is the general form of a typical decision making structure found in most of the programming languages −

C++ programming language provides following types of decision making statements.

The ? : Operator

We have covered conditional operator “? :” in previous chapter which can be used to replace if…else statements. It has the following general form −

Exp1 ? Exp2 : Exp3;

Exp1, Exp2, and Exp3 are expressions. Notice the use and placement of the colon.

The value of a ‘?’ expression is determined like this: Exp1 is evaluated. If it is true, then Exp2 is evaluated and becomes the value of the entire ‘?’ expression. If Exp1 is false, then Exp3 is evaluated and its value becomes the value of the expression.

There may be a situation, when you need to execute a block of code several number of times. In general, statements are executed sequentially: The first statement in a function is executed first, followed by the second, and so on.

Programming languages provide various control structures that allow for more complicated execution paths.

A loop statement allows us to execute a statement or group of statements multiple times and following is the general from of a loop statement in most of the programming languages −

C++ programming language provides the following type of loops to handle looping requirements.

Loop Control Statements

Loop control statements change execution from its normal sequence. When execution leaves a scope, all automatic objects that were created in that scope are destroyed.

C++ supports the following control statements.

The Infinite Loop

A loop becomes infinite loop if a condition never becomes false. The for loop is traditionally used for this purpose. Since none of the three expressions that form the ‘for’ loop are required, you can make an endless loop by leaving the conditional expression empty.

#include <iostream>
using namespace std;
 
int main () {
   for( ; ; ) {
  printf("This loop will run forever.\n");
   }

   return 0;
}

When the conditional expression is absent, it is assumed to be true. You may have an initialization and increment expression, but C++ programmers more commonly use the ‘for (;;)’ construct to signify an infinite loop.

An operator is a symbol that tells the compiler to perform specific mathematical or logical manipulations. C++ is rich in built-in operators and provide the following types of operators −

• Arithmetic Operators
• Relational Operators
• Logical Operators
• Bitwise Operators
• Assignment Operators
• Misc Operators

This chapter will examine the arithmetic, relational, logical, bitwise, assignment and other operators one by one.

Arithmetic Operators

There are following arithmetic operators supported by C++ language −

Assume variable A holds 10 and variable B holds 20, then −

Relational Operators

There are following relational operators supported by C++ language

Assume variable A holds 10 and variable B holds 20, then −

Logical Operators

There are following logical operators supported by C++ language.

Assume variable A holds 1 and variable B holds 0, then −

Bitwise Operators

Bitwise operator works on bits and perform bit-by-bit operation. The truth tables for &, |, and ^ are as follows −

Assume if A = 60; and B = 13; now in binary format they will be as follows −

A = 0011 1100

B = 0000 1101

—————–

A&B = 0000 1100

A|B = 0011 1101

A^B = 0011 0001

~A  = 1100 0011

The Bitwise operators supported by C++ language are listed in the following table. Assume variable A holds 60 and variable B holds 13, then −

Assignment Operators

There are following assignment operators supported by C++ language −

Misc Operators

The following table lists some other operators that C++ supports.

Operators Precedence in C++

Operator precedence determines the grouping of terms in an expression. This affects how an expression is evaluated. Certain operators have higher precedence than others; for example, the multiplication operator has higher precedence than the addition operator −

For example x = 7 + 3 * 2; here, x is assigned 13, not 20 because operator * has higher precedence than +, so it first gets multiplied with 3*2 and then adds into 7.

Here, operators with the highest precedence appear at the top of the table, those with the lowest appear at the bottom. Within an expression, higher precedence operators will be evaluated first.

A storage class defines the scope (visibility) and life-time of variables and/or functions within a C++ Program. These specifiers precede the type that they modify. There are following storage classes, which can be used in a C++ Program

• auto
• register
• static
• extern
• mutable

The auto Storage Class

The auto storage class is the default storage class for all local variables.

{
   int mount;
   auto int month;
}

The example above defines two variables with the same storage class, auto can only be used within functions, i.e., local variables.

The register Storage Class

The register storage class is used to define local variables that should be stored in a register instead of RAM. This means that the variable has a maximum size equal to the register size (usually one word) and can’t have the unary ‘&’ operator applied to it (as it does not have a memory location).

{
   register int  miles;
}

The register should only be used for variables that require quick access such as counters. It should also be noted that defining ‘register’ does not mean that the variable will be stored in a register. It means that it MIGHT be stored in a register depending on hardware and implementation restrictions.

The static Storage Class

The static storage class instructs the compiler to keep a local variable in existence during the life-time of the program instead of creating and destroying it each time it comes into and goes out of scope. Therefore, making local variables static allows them to maintain their values between function calls.

The static modifier may also be applied to global variables. When this is done, it causes that variable’s scope to be restricted to the file in which it is declared.

In C++, when static is used on a class data member, it causes only one copy of that member to be shared by all objects of its class.

#include <iostream>
 
// Function declaration
void func(void);
 
static int count = 10; /* Global variable */
 
main() {
   while(count--) {
  func();
   }
   
   return 0;
}

// Function definition
void func( void ) {
   static int i = 5; // local static variable
   i++;
   std::cout << "i is " << i ;
   std::cout << " and count is " << count << std::endl;
}

When the above code is compiled and executed, it produces the following result −

i is 6 and count is 9
i is 7 and count is 8
i is 8 and count is 7
i is 9 and count is 6
i is 10 and count is 5
i is 11 and count is 4
i is 12 and count is 3
i is 13 and count is 2
i is 14 and count is 1
i is 15 and count is 0

The extern Storage Class

The extern storage class is used to give a reference of a global variable that is visible to ALL the program files. When you use ‘extern’ the variable cannot be initialized as all it does is point the variable name at a storage location that has been previously defined.

When you have multiple files and you define a global variable or function, which will be used in other files also, then extern will be used in another file to give reference of defined variable or function. Just for understanding extern is used to declare a global variable or function in another file.

The extern modifier is most commonly used when there are two or more files sharing the same global variables or functions as explained below.

First File: main.cpp

#include <iostream>
int count ;
extern void write_extern();
 
main() {
   count = 5;
   write_extern();
}

Second File: support.cpp

#include <iostream>

extern int count;

void write_extern(void) {
   std::cout << "Count is " << count << std::endl;
}

Here, extern keyword is being used to declare count in another file. Now compile these two files as follows −

$g++ main.cpp support.cpp -o write

This will produce write executable program, try to execute write and check the result as follows −

$./write
5

The mutable Storage Class

The mutable specifier applies only to class objects, which are discussed later in this tutorial. It allows a member of an object to override const member function. That is, a mutable member can be modified by a const member function.

C++ allows the char, int, and double data types to have modifiers preceding them. A modifier is used to alter the meaning of the base type so that it more precisely fits the needs of various situations.

The data type modifiers are listed here −

• signed
• unsigned
• long
• short

The modifiers signed, unsigned, long, and short can be applied to integer base types. In addition, signed and unsigned can be applied to char, and long can be applied to double.

The modifiers signed and unsigned can also be used as prefix to long or short modifiers. For example, unsigned long int.

C++ allows a shorthand notation for declaring unsigned, short, or long integers. You can simply use the word unsigned, short, or long, without int. It automatically implies int. For example, the following two statements both declare unsigned integer variables.

unsigned x;
unsigned int y;

To understand the difference between the way signed and unsigned integer modifiers are interpreted by C++, you should run the following short program −

#include <iostream>
using namespace std;
 
/* This program shows the difference between
   * signed and unsigned integers.
*/
int main() {
   short int i;           // a signed short integer
   short unsigned int j;  // an unsigned short integer

   j = 50000;

   i = j;
   cout << i << " " << j;

   return 0;
}

When this program is run, following is the output −

-15536 50000

The above result is because the bit pattern that represents 50,000 as a short unsigned integer is interpreted as -15,536 by a short.

Type Qualifiers in C++

The type qualifiers provide additional information about the variables they precede.

Constants refer to fixed values that the program may not alter and they are called literals.

Constants can be of any of the basic data types and can be divided into Integer Numerals, Floating-Point Numerals, Characters, Strings and Boolean Values.

Again, constants are treated just like regular variables except that their values cannot be modified after their definition.

Integer Literals

An integer literal can be a decimal, octal, or hexadecimal constant. A prefix specifies the base or radix: 0x or 0X for hexadecimal, 0 for octal, and nothing for decimal.

An integer literal can also have a suffix that is a combination of U and L, for unsigned and long, respectively. The suffix can be uppercase or lowercase and can be in any order.

Here are some examples of integer literals −

212         // Legal
215u        // Legal
0xFeeL      // Legal
078         // Illegal: 8 is not an octal digit
032UU       // Illegal: cannot repeat a suffix

Following are other examples of various types of Integer literals −

85         // decimal
0213       // octal
0x4b       // hexadecimal
30         // int
30u        // unsigned int
30l        // long
30ul       // unsigned long

Floating-point Literals

A floating-point literal has an integer part, a decimal point, a fractional part, and an exponent part. You can represent floating point literals either in decimal form or exponential form.

While representing using decimal form, you must include the decimal point, the exponent, or both and while representing using exponential form, you must include the integer part, the fractional part, or both. The signed exponent is introduced by e or E.

Here are some examples of floating-point literals −

3.14159       // Legal
314159E-5L    // Legal
510E          // Illegal: incomplete exponent
210f          // Illegal: no decimal or exponent
.e55          // Illegal: missing integer or fraction

Boolean Literals

There are two Boolean literals and they are part of standard C++ keywords −

• A value of true representing true.
• A value of false representing false.

You should not consider the value of true equal to 1 and value of false equal to 0.

Character Literals

Character literals are enclosed in single quotes. If the literal begins with L (uppercase only), it is a wide character literal (e.g., L’x’) and should be stored in wchar_t type of variable . Otherwise, it is a narrow character literal (e.g., ‘x’) and can be stored in a simple variable of char type.

A character literal can be a plain character (e.g., ‘x’), an escape sequence (e.g., ‘\t’), or a universal character (e.g., ‘\u02C0’).

There are certain characters in C++ when they are preceded by a backslash they will have special meaning and they are used to represent like newline (\n) or tab (\t). Here, you have a list of some of such escape sequence codes −

Following is the example to show a few escape sequence characters −

#include <iostream>
using namespace std;

int main() {
   cout << "Hello\tWorld\n\n";
   return 0;
}

When the above code is compiled and executed, it produces the following result −

Hello   World

String Literals

String literals are enclosed in double quotes. A string contains characters that are similar to character literals: plain characters, escape sequences, and universal characters.

You can break a long line into multiple lines using string literals and separate them using whitespaces.

Here are some examples of string literals. All the three forms are identical strings.

"hello, dear"

"hello, \

dear"

"hello, " "d" "ear"

Defining Constants

There are two simple ways in C++ to define constants −

• Using #define preprocessor.
• Using const keyword.

The #define Preprocessor

Following is the form to use #define preprocessor to define a constant −

#define identifier value

Following example explains it in detail −

#include <iostream>
using namespace std;

#define LENGTH 10   
#define WIDTH  5
#define NEWLINE '\n'

int main() {
   int area;  
   
   area = LENGTH * WIDTH;
   cout << area;
   cout << NEWLINE;
   return 0;
}

When the above code is compiled and executed, it produces the following result −

50

The const Keyword

You can use const prefix to declare constants with a specific type as follows −

const type variable = value;

Following example explains it in detail −

#include <iostream>
using namespace std;

int main() {
   const int  LENGTH = 10;
   const int  WIDTH  = 5;
   const char NEWLINE = '\n';
   int area;  
   
   area = LENGTH * WIDTH;
   cout << area;
   cout << NEWLINE;
   return 0;
}

When the above code is compiled and executed, it produces the following result −

50

Note that it is a good programming practice to define constants in CAPITALS.