Chapter 5

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Chapter 5 - PowerPoint PPT Presentation

Chapter 5. Names Variables Scope Lifetime. Outline. Some Exercises in C++ Names Variables Scope Lifetime. Some Exercises in C++. اكتب برنامج يستطيع حساب مساحة المستطيل حيث أن الطول و العرض يقوم المستخدم بادخاله، علما بان مساحة المستطيل = الطول * العرض.

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Presentation Transcript

Chapter 5

Names

Variables

Scope

Outline
• Some Exercises in C++
• Names
• Variables
• Scope
Some Exercises in C++
• اكتب برنامج يستطيع حساب مساحة المستطيل حيث أن الطول و العرض يقوم المستخدم بادخاله، علما بان مساحة المستطيل = الطول * العرض.
• اكتب برنامج يقوم بحساب معدل الصرف الاسبوعي لشخص ما؟
Names
• Names
• Names are associated with variable ,lables ,sub-programs , formal parameters and other program constructs such as class.
• Design issues=
• Are the names case-sensitive ?
Names
• Ok ? what is a name in a programming language ?
• It’s a string of characters used to identify some entities in a program .
Names

Fortran : allows space in names sum of salaries sum of salaries .

C++ : case –sensitive

Rose ≠ ROSE ≠ rose

This will take us back to How can we evaluate any language by writbility and readability .

Names

اﻟﻜﻠﻤﺎت اﻟﻤﺤﺠﻮزة (Reserved words )

Names

How to name in C++:

•  names must begin with a letter of the alphabet or an underscore( _ )
• After the first initial letter, variable names can also contain letters and numbers.  No spaces or special characters, however, are allowed.
• Uppercase characters are distinct from lowercase characters.  Using all uppercase letters is used primarily to identify constant variables.
• You cannot use a C++ keyword (reserved word) as a variable name
Variable
• It  is a storage location and an associated symbolic name (an identifier) which contains some known or unknown quantity or information, a value
• Attributes
• Names: same conditions previously.
• Type= int , char, float, double, …..
• Address: the place in the memory.
• Value: content of the memory.
Scope

Scope

Every variable has a scope : So the scope of a variable is the range of statements in which the variable is visible .

• The scope of a variable is from its declaration to the end of the method.
• The lifetime of a variable is the period of time beginning when the method is entered and ending when execution of the method terminates.

#include<iostream>

using namespace std;

int main()

{

intx = 10 ;

Sum();

for (inti =0; i<5 ; i++)

{ cout << “ Test “ ; }

}

void Sum()

{

intx = 100 ;

cout <<“ X = “ <<x ;

}