Basic Elements of C++

Introduction to Computer Programming Basic Elements of C++ C++ Programming: From Problem Analysis to Program Design 1

Chapter Topics • The Basics of a C++ Program • Data Types • Arithmetic Operators and Operator Precedence • Expressions • Input • Increment and Decrement Operators • Output • Preprocessor Directives • Program Style and Form 2

The Basics of a C++ Program • A C++ program is a collection of one or more subprograms (functions) • Function – Collection of statements – Statements accomplish a task • Every C++ program has a function called: main 3

Example Program #include <iostream> using namespace std; int main() { cout<<"Welcome to C++ Programming"<<endl; return 0; } Welcome to C++ Programming Program Output: 4

The Basics of a C++ Program • Programming language – a set of rules, symbols, special words • Rules – syntax – specifies legal instructions • Symbols – special symbols ( + - * ! … ) • Special words – reserved words – (int, float, double, char …) 5

Identifiers • Rules for identifiers – must begin with letter or the underscore “_” – followed by any combination of numerals or letters – recommend meaningful identifiers • Evaluate the following ElectricCharge 23Skidoo _snarFbLat 6

Data Types • Definition: – a set of values – combined with a set of operations 7 Simple: int, float, char, bool, etc… Structured: A collection of simple data types Pointers: Points to address

Data Types • Simple data types include – Integers – Floating point – Enumeration • Integer data types include char short int long bool Numbers, symbols, letters Values true and false only 8 Numbers without decimals

Number Data Types Integer & Decimal 9

Floating‐Point Types (Decimal) • Stored using scientific notation – the sign of the number, – the significant digits of the number – the sign of the power of 10 – the power of 10 10

Data Types • Different floating‐ point types • Note that various types will – have different ranges of values – require different amounts of memory 11

Data Types • The string Type – a programmer‐defined type – requires #include <string> • A string is a sequence of characters "Hi Mom" "We're Number 1!" "75607" 12

Arithmetic Operators and Operator Precedence • Common operators for calculations + - * / % • Precedence same as in algebraic usage – Inside parentheses done first – Next * / % from left to right – Then + and - from left to right 13

Expressions • An expression includes – constants – variables – function calls – combined with operators 3 / 2 + 5.0 Ans: 6 sin(x) + sqrt(y) 14

Expressions • Expressions can include – values all of the same type 3 + 5 * 12 – 7 Ans: 56 – values of different (compatible) types 1.23 * 18 / 9.5 Ans: 2.33053 • An operation is evaluated according to the types of the operands – if they are the same, the result is the type of the operands – if the operands are different (int and float) then the result is float 15

Type Casting • Implicit change of type can occur – when operands are of different type • It is possible to explicitly specify that an expression be converted to a different type static_cast < type > (expression) static_cast <int> (3.5 * 6.9 / 2.1) Ans: 11 16

Input • Storing data in the computer's memory requires two steps 1. Allocate the memory by declaring a variable 2. Have the program fetch a value from the input device and place it in the allocated memory location x 123 cin >> x 17 int x; 123 will be stored in x

Allocating Memory • Variable – A memory location whose content may change during program execution • Declaration: – Syntax: type identifier; – Example: double x; (declaration) int y = 45; (declaration and initialization) Note optional initialization of the variable 18

Allocating Memory • Named Constant – A memory location whose content cannot be changed • Declaration – Syntax: const type identifier = value; – Example const double PI = 3.14159; Note required initialization of the named constant 19

Putting Data Into Variables Data can be put into a variable through either: 1. At initialization time (by programmer) int x=5; 2. Assignment statement (by programmer) – Syntax: variable = expression; – Example x = 1.234; volume = sqr (base) * height; 3. Input (read) statement (by user) – Syntax: cin >> variable ; – Example cin >> height; 20

Increment and Decrement Operators • Pre‐increment ++x; equivalent to x = x + 1; • Pre‐decrement --x; equivalent to x = x - 1; – Pre‐(increment/decrement): Changes the value before execution of a statement – Post‐(increment/decrement): Changes the value after execution of the statement 21 Post‐increment x++; equivalent to x = x + 1; Post‐decrement x--; equivalent to x = x - 1;

Output • Values sent to an output device – Usually the screen – Can also be a file or some device • Syntax for screen output: cout << expression << … • Example cout << "The total is "<< sum << endl; Output command Insertion operator Values to be printed New line 22 Text to be displayed

Output • Escape sequences also used to manipulate output cout << "The total ist "<< sum << endl; 23

Preprocessor Directives • Commands supplied to the preprocessor – Runs before the compiler – Modifies the text of the source code before the compiler starts • Syntax – start with # symbol – #include <headerFileName> • Example: #include <iostream> 24

Preprocessor Directives • Note the preprocessor step in the sequence 25

Namespace • The #include <iostream> command is where cin and cout are declared • They are declared within a namespace called std • When we specify using namespace std; – Then we need not preface the cin and cout commands with std::cin and std::cout 26

Program Style and Form • Every program must contain a function called main int main () { … return 0; } • The int specifies that it returns an integer value • Also you can use void main( ) { … } • The void specifies there will be no return value 27

Program Style and Form • Variables usually declared – inside main – at beginning of program • Use blanks and space to make the program easy for humans to read • Semicolons ; required to end a statement • Commas used to separate things in a list int x,y,z; 28

Program Style and Form • Documentation – Comments specified between /* this is a comment */ and following // also a comment – Always put at beginning of program /* name, date, cpo, purpose of program */ 29

Program Style and Form • Names of identifiers should help document program double electricCharge; // instead of ec • Prompt keyboard entry cout << "Enter the value for x -> "; cin >> x; 30

Basic Elements of C++

More Related Content

What's hot

Similar to Basic Elements of C++

More from Jason J Pulikkottil

Recently uploaded

Basic Elements of C++