Copyright 2006 Addison-Wesley Brief Version of Starting Out with C++ Chapter 2 Introduction to C++

Chapter 2 slide 2 Topics Lecture The char Data Type 2.8 Floating-Point Data Types 2.9 The bool Data Type 2.10 Determining the Size of a Data Type 2.11 Variable Assignments and Initialization 2.12 Scope 2.13 Arithmetic Operators 2.14 Comments 2.15 Programming Style 2.16 Standard and Prestandard C++

Chapter 2 slide The char Data Type Used to hold characters or very small integer values Usually 1 byte of memory Numeric value of character from character set is stored in memory: CODE: char letter; letter = 'C'; MEMORY: letter 67

Chapter 2 slide 4 Text data Type Character (represented by 1 Byte) String (stores a number of Characters). –The size of the string depends on the number of characters involved. ASCII Values of Commonly used Characters: 0 to 948 to 57 A to Z65 to 90 a to z 97 to 122

Chapter 2 slide 5 ASSCII Characters #include int main() { for (int i =0; i<256; i++) cout<< i << " "<<char(i)<<" "; return 0; }

Chapter 2 slide 6 Character Strings Can store a series of characters in consecutive memory locations: "Hello" Stored with the null terminator, \0, at the end: Comprised of the characters between the " " Hello\0

Chapter 2 slide 7 Strings in C++ For the C++.net and DEV compilers, we can declare a strings as: string MyName; cin >> MyName; cout<<MyName As long as the name has no spaces. char MyName[20]; cin >> MyName; cout <<MyName; Use getline when you are reading a line of char.. See next example.

Chapter 2 slide 8 Strings in C++ A better way for declaring strings to accommodate Turbo C++ Compiler int constant size = 20; char MyName[size]; cin >> MyName; cout <<MyName; Chapter 11.. Full details typedef, getline(), getchar() … later For the Dev compiler: String data type is valid, just make sure that you include the string library

Chapter 2 slide 9 // using the string data type #include using namespace std; int main() { const int size =15; Char name[size]; // can't have a space int t1, t2, t3; int sum; cout<< " name? \n"; cin >> name; // no space cout << "T1 ?"; cin >> t1; cout << "T2 ?"; cin >> t2; cout << "T3 ?"; cin >> t3; sum = t1 + t2 + t3; cout<< name<< " " <<t1<<" "<< t2<<" "<<t3<< " "<< sum<<"\n"; system("pause"); return 0; }

Chapter 2 slide 10 #include using namespace std; int main() { char name[80]; // can’t have a space int t1, t2, t3; int sum; cout<< " name? \n"; cin.getline(name,sizeof(name)); // including a space cout << "T1 ?"; cin >> t1; cout << "T2 ?"; cin >> t2; cout << "T3 ?"; cin >> t3; sum = t1 + t2 + t3; cout<< name<< " " <<t1<<" "<< t2<<" "<<t3<< " "<< sum<<"\n"; system("pause"); return 0; }

Chapter 2 slide Floating-Point Data Types Designed to hold real numbers Stored in a form similar to scientific notation All numbers are signed Available in different sizes (number of bytes): float, double, and long double Size of float  size of double  size of long double

Chapter 2 slide 12 Floating Point Also known as Real number (numbers with a fraction). Types and ranges: Data TypeSize in bytesRange in E notation float4+-3.4E-38 to +-3.4E38 Double8+-1.7E-308 to +-1.7E308 Long double10 or E-4932 to E4932

Chapter 2 slide 13 Floating-point Constants Can be represented in -Fixed point (decimal) notation: E notation: E16.25e-5 Are double by default Can be forced to be float ( f ) or long double ( L ) More on type casting slide 43

Chapter 2 slide 14 Represents values that are true or false bool variables are stored as small integers false is represented by 0, true by 1: bool allDone = true; bool finished = false; More on the Boolean representation.. later 2.9 The bool Data Type allDone 10 finished

Chapter 2 slide 15

Chapter 2 slide Determining the Size of a Data Type The sizeof operator gives the size of any data type or variable: double amount; cout << "A double is stored in " << sizeof(double) << "bytes\n"; cout << "Variable amount is stored in " << sizeof(amount) << "bytes\n";

Chapter 2 slide 17 Assigning “Compatible” data Type Assign strings to string type, integers to integer type, float to float type and so on ! string Lname = “Aljamal”; char Lname[ ]= “Aljamal”; int my_name; my_name = 198; Cout << “My Name is ” <<my_name; Out put will be My Name is 198 Sounds “ STUPID” !! Unless you are called by a code number !!

Chapter 2 slide Variable Assignments and Initialization Assignment: Uses the = operator Has a single variable on the left side and a value (constant, variable, or expression) on the right side Copies the value on the right into the variable on the left: item = 12;

Chapter 2 slide 19 Variable Assignments and Initialization Initialize a variable: assign it a value when it is defined: int length = 12; Can initialize some or all variables: int length = 12, width = 5, area;

Chapter 2 slide Scope The scope of a variable: where the program can access the variable A variable cannot be used before it is defined

Chapter 2 slide 21 Constants A modifier specifying that variable to remain a constant value when used in declaration statement. Form:const double x = 7.65; const float PI = 3.14; The value in the constant must be assigned when declared. The program is not allowed to change the value while it is running, if we need to change the value, we have to change the code then re compile it.

Chapter 2 slide 22 Where can we declare the Variables in the program? Inside a function. Outside a function. In a function header. For now lets declare our variables inside our main function, which is our main program. BUT: we always MUST declare variables before using them.

Chapter 2 slide Arithmetic Operators Used for performing numeric calculations C++ has unary, binary, and trinary operators: –unary (1 operand) -5 –binary (2 operands) –ternary (3 operands) exp1 ? exp2 : exp3

Chapter 2 slide 24 Binary Arithmetic Operators SYMBOLOPERATIONEXAMPLEVALUE OF ans + addition ans = 7 + 3;10 - subtraction ans = 7 - 3;4 * multiplication ans = 7 * 3;21 / division ans = 7 / 3;2 % modulus ans = 7 % 3;1

Chapter 2 slide 25 / Operator / (division) operator performs integer division if both operands are integers cout << 13 / 5; // displays 2 cout << 91 / 7; // displays 13 If either operand is floating point, the result is floating point cout << 13 / 5.0; // displays 2.6 cout << 91.0 / 7; // displays 13.0

Chapter 2 slide 26 % Operator % (modulus) operator computes the remainder resulting from integer division cout << 13 % 5; // displays 3 % requires integers for both operands cout << 13 % 5.0; // error

Chapter 2 slide Comments Used to document parts of the program Intended for persons reading the source code of the program: –Indicate the purpose of the program –Describe the use of variables –Explain complex sections of code Are ignored by the compiler

Chapter 2 slide 28 Casting Casting: an operation in which the value of one type of data is transformed into another type of data. General form: double x = 3.5; int y; y = (int) x; // casts x into an int

Chapter 2 slide 29 C++ Style Comments Begin with // through to the end of line: int length = 12; // length in inches int width = 15; // width in inches int area; // calculated area // calculate rectangle area area = length * width;

Chapter 2 slide 30 C-Style Comments Begin with /*, end with */ Can span multiple lines: /* this is a multi-line C-style comment */ Can be used like C++ style comments: int area; /* calculated area */

Chapter 2 slide Programming Style The visual organization of the source code Includes the use of spaces, tabs, and blank lines –Does not affect the syntax of the program –Affects the readability of the source code

Chapter 2 slide 32 Programming Style Common elements to improve readability: Braces { } aligned vertically Indentation of statements within a set of braces Blank lines between declaration and other statements Long statements wrapped over multiple lines with aligned operators

Copyright 2006 Addison-Wesley Brief Version of Starting Out with C++ Chapter 2 Introduction to C++