Chapter 5

1. Chapter 5 Names Variables Scope Lifetime

2. Outline • Some Exercises in C++ • Names • Variables • Scope • Lifetime

3. 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؟

4. 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 ?

5. Names • Ok ? what is a name in a programming language ? • It’s a string of characters used to identify some entities in a program .

6. 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 .

7. Names اﻟﻜﻠﻤﺎت اﻟﻤﺤﺠﻮزة (Reserved words )

8. 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

9. 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.

10. 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.

11. 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.

12. #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 ; }