LECTEURE # 5 : STRUCTURED PROGRAMMING VARIABLES, INPUT, MEMORY المتغيرات, المدخلات, الذاكرة By Mr. Ali Edan

Content 2  Variables المتغيرات  C++ Built in data types انواع البيانات والمتغيرات  C++ variable declaration syntax طريقة تعريف المتغيرات  cin statement امر ادخال البيانات  Local and global variables المتغير المحلي والمتغير العمومي  Scope resolution operator (::) الاداة  Variables and RAM المتغيرات والذاكرة  Defining constants الثوابت

Variable  Location on computer’s memory to store data then use and change its value in a program  جزء من الذاكرة لخزن نوع محدد من البيانات  Each variable has كل متغير لدية 1. Name (identifier) اسم Series of letters, digits, underscores Not a keyword Start with a letter Case sensitive Meaningful 2. Type نوع Programmer-defined احد انواع البيانات 3

Determine which of the following variables name is valid or invalid : _under_bar_z2h22 2h67h2his_account_total t587m her_sales3gj7 abc 4

C++ Built-in Data Types  Called fundamental types or primitives types: numeric, character, logical الانواع الاساسية : ارقام, حرفي, منطقية 5

الانواع المنطقية bool Data Type  Has two values, true and false  قيمتين صح و خطأ  Manipulate logical (Boolean) expressions  تستخدم في المعادلات المنطقية  true and false are called logical values  قيم هذا المتغيرات هي true & false  bool, true, and false are reserved words  الكلمات المحجوزة هي true,false, bool 6

نوع char Data Type  Used for characters  letters, digits, and special symbols  حروف, رموز, رموز خاصة  Each character is enclosed in single quotes  Examples: 'A', 'a', '0', '*', '+', '$', '&'  A blank space is a character and is written ' ' with a space left between the single quotes 7

Declaring Variables  All variables must be declared anywhere in program with a name and data type before they used  كل انواع المتغيرات يحب ان تعرف قبل ان تستخدم  Syntax rule: begin with a data type then variable name  النوع يكتب قبل اسم المتغير  Variables of the same type can be declared in  Multiple lines  One line separated by commas 8 int num1; int num2; int num3; int num1, num2, num3; int num1; int num2; int num3; int num1, num2, num3; dataType varName;

اعطاء قيم للمتغيرات Initializing Variable  Variables can be initialized once declared  first and second are int variables with the values 13 and 10, respectively  ch is a char variable whose value is empty  x and y are double variables with 12.6 and , respectively 9 int first=13, second=10; char ch=' '; double x=12.6, y= ; int first=13, second=10; char ch=' '; double x=12.6, y= ;

Using cin  Namespace  std:: Specifies using a name that belongs to “namespace” std Can be removed through use of using statements  Standard output stream object  std::cin “Connected” to keyboard Defined in input/output stream header file 10

Using cin (cont.)  Stream extraction operator >>  Value to left (left operand) inserted into right operand  Waits for user to input value then press Enter key  Example std::cin >> num1; Inserts the standard input from keyboard into variable num1  Prints message before cin statement to direct the user to take a specification called prompt  cin and cout facilitate interaction between user and program 11

12 Enter first integer 45 Enter second integer 72 Sum is // Fig. 2.5: fig02_05.cpp 2 // Addition program that display the sum of two numbers. 3 #include // allow program to perform input and output 4 5 // function main begins program execution 6 int main() 7 { 8 // variable declaration 9int number1; // first integer to add 10 int number2; // second integer to add 11 int sum; // sum of number1 and number std::cout << "Enter first integer: \n"; // prompt user for data 14 std::cin >> number1; // read first integer from user to number std::cout << "Enter second integer: \n"; // prompt user for data 17 std::cin >> number2; // read second integer from user to number sum = number1 + number2; // add the numbers; stor result in sum std::cout << "Sum is " << sum << std::endl; // display sum; end line return 0; // indicate that program ended successfully 24 } // end function main Declare integer variables.Use stream extraction operator with standard input stream to obtain user input. Stream manipulator std::endl outputs a newline, then “flushes output buffer.” Concatenating, chaining or cascading stream insertion operations. Calculations can be performed in output statements: alternative for lines 19 and 21: std::cout << "Sum is " << number1 + number2 << std::endl;

Variable Scope  Portion of the program where the variable can be used  Scope can be  Local  Global 13

Local Variables  Defined within a module  Can be seen and used only by module itself  Store temporally in memory  Erased when the module terminates 14 int main() { int i; char a; return 0; } int main() { int i; char a; return 0; }

Global Variables  Defined outside any module  Used and seen by all modules  Variable name can be duplicated within and outside a modules  Differentiate between them by using unary scope resolution operator (::) 15 int i; int main() { char a; return 0; } int i; int main() { char a; return 0; }

Exercise Write a program that declares two constant A and B 2. Initialize A =1 and B= Declare an int named C and float named D 4. Initialize C =A and D=B 5. Write statements to print C and D to screen

End 17