Chapter 5
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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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Chapter 5

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Chapter 5

Chapter 5

Names

Variables

Scope

Lifetime


Outline

Outline

  • Some Exercises in C++

  • Names

  • Variables

  • Scope

  • Lifetime


Some exercises in c

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

    • Names are associated with variable ,lables ,sub-programs , formal parameters and other program constructs such as class.

    • Design issues=

      • Are the names case-sensitive ?


Names1

Names

  • Ok ? what is a name in a programming language ?

    • It’s a string of characters used to identify some entities in a program .


Names2

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 .


Names3

Names

اﻟﻜﻠﻤﺎت اﻟﻤﺤﺠﻮزة (Reserved words )


Names4

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

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

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.


Lifetime

Lifetime

  • The lifetime of a variable is the period of time beginning when the method is entered and ending when execution of the method terminates.


Chapter 5

#include<iostream>

using namespace std;

int main()

{

intx = 10 ;

int grade;

Sum();

cout << “Grade” << grade ;

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

{ cout << “ Test “ ; }

}

void Sum()

{

intx = 100 ;

cout <<“ X = “ <<x ;

}


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