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Variable names are also selected according to the rules of identifiers:

  • Identifiers must begin with an uppercase or lowercase ASCII letter or an underscore (_).
  • You can use digits in an identifier, but not as the first character. You are not allowed to use special characters such as $,&, * or %.
  • Reserved words cannot be used for variable names.

Example: Some valid identifiers

my_variable

Temperature

x1

x2

_my_variable

Some invalid identifiers are as follows:

%x1%my_var@x2

We should always give variables meaningful names, from which a reader might be able to make a reasonable guess at their purpose. We may use comments if further clarification is necessary.

Declaration statements

Naming a variable and specifying the data type that can be stored in it is accomplished using declaration statement . A declaration statement in C++ programs has the following syntax:

type name;

The type portion refers to the data type of the variable.

The data type determines the type of information that can be stored in the variable.

Example:

int sum;

long datenem;

double secnum;

Note:

  1. A variable must be declared before it can be used.
  2. Declaration statements can also be used to store an initial value into declared variables.

Example:

int num = 15;

float grade1 = 87.0;

Variable declarations are just the instructions that tell the compiler to allocate memory locations for the variables to be used in a program.

A variable declaration creates a memory location but it is undefined to start with, that means it's empty.

Example

#include<iostream.h>

int main()

{

float price1 = 85.5;

float price2 = 97.0;

float total, average;

total = price1 + price2;

average = total/2.0; // divide the total by 2.0

cout<<"The average price is "<<average<<endl;

return 0;

}

The output of the above program:

The average price is 91.25

Let notice the two statements in the above program:

total = price1 + price2;

average = total/2.0;

Each of these statements is called an assignment statement because it tells the computer to assign (store) a value into a variable. Assignment statements always have an equal (=) sign and one variable name on the left of this sign. The value on the right of the equal sign is assigned to the variable on the left of the equal sign.

Display a variable’s address

Every variable has three major items associated with it: its data type, its actual value stored in the variable and the address of the variable. The value stored in the variable is referred to as the variable’s contents, while the address of the first memory location used for the variable constitutes its address.

To see the address of a variable, we can use address operator ,&, which means “the address of “. For example,&num means the address of num.

Example

#include<iostream.h>

int main()

{

int a;

a = 22;

cout<<"The value stored in a is "<<a<<endl;

cout<<"The address of a = "<<&a<<endl;

return 0;

}

The output of the above program:

The value stored in a is 22

The address of a = 0x0065FDF4

The display of addresses is in hexadecimal notation.

Integer quantifiers

Portable languages like C++ must have flexible data type sizes. Different applications might need integers of different sizes. C++ provides long integer , short integer , and unsigned integer data types. These three additional integer data types are obtained by adding the quantifier long , short or unsigned to the normal integer declaration statements.

Questions & Answers

the diagram of the digestive system
Assiatu Reply
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Ogenrwot
How does twins formed
William Reply
They formed in two ways first when one sperm and one egg are splited by mitosis or two sperm and two eggs join together
Oluwatobi
what is genetics
Josephine Reply
Genetics is the study of heredity
Misack
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Misack
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Hassan Reply
discuss biological phenomenon and provide pieces of evidence to show that it was responsible for the formation of eukaryotic organelles
Joseph Reply
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Yousuf Reply
the study of living organisms and their interactions with one another and their environments
AI-Robot
the study of living organisms and their interactions with one another and their environment.
Wine
discuss the biological phenomenon and provide pieces of evidence to show that it was responsible for the formation of eukaryotic organelles in an essay form
Joseph Reply
what is the blood cells
Shaker Reply
list any five characteristics of the blood cells
Shaker
lack electricity and its more savely than electronic microscope because its naturally by using of light
Abdullahi Reply
advantage of electronic microscope is easily and clearly while disadvantage is dangerous because its electronic. advantage of light microscope is savely and naturally by sun while disadvantage is not easily,means its not sharp and not clear
Abdullahi
cell theory state that every organisms composed of one or more cell,cell is the basic unit of life
Abdullahi
is like gone fail us
DENG
cells is the basic structure and functions of all living things
Ramadan
What is classification
ISCONT Reply
is organisms that are similar into groups called tara
Yamosa
in what situation (s) would be the use of a scanning electron microscope be ideal and why?
Kenna Reply
A scanning electron microscope (SEM) is ideal for situations requiring high-resolution imaging of surfaces. It is commonly used in materials science, biology, and geology to examine the topography and composition of samples at a nanoscale level. SEM is particularly useful for studying fine details,
Hilary
cell is the building block of life.
Condoleezza Reply
what is cell divisoin?
Aron Reply
Diversity of living thing
ISCONT
what is cell division
Aron Reply
Cell division is the process by which a single cell divides into two or more daughter cells. It is a fundamental process in all living organisms and is essential for growth, development, and reproduction. Cell division can occur through either mitosis or meiosis.
AI-Robot
What is life?
Allison Reply
life is defined as any system capable of performing functions such as eating, metabolizing,excreting,breathing,moving,Growing,reproducing,and responding to external stimuli.
Mohamed
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Source:  OpenStax, Programming fundamentals in c++. OpenStax CNX. Jul 29, 2009 Download for free at http://cnx.org/content/col10788/1.1
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