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Introducing C++ Elements

Introducing C++ Elements. Outline. Main algorithms’ constructs General form of a C++ program {section 2.5} C++ language elements {section 2.1} Executable statements {section 2.4} Reserved words and symbols {section 2.2} Data types {section 2.3}. Main Algorithms’ Constucts.

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Introducing C++ Elements

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  1. Introducing C++ Elements

  2. Outline • Main algorithms’ constructs • General form of a C++ program {section 2.5} • C++ language elements {section 2.1} • Executable statements {section 2.4} • Reserved words and symbols {section 2.2} • Data types {section 2.3} CSCE 106

  3. Main Algorithms’ Constucts • An algorithm is written as a step-by-step procedure (sequence) in which choices can be made where necessary (selection), and all or part of the algorithm can be repeated (repetition). • Thus, the basic control structures of algorithms are: 1- Sequence 2- Selection 3- Repetition CSCE 106

  4. Sequence • An algorithm is based on the notion of sequence, which is the ordering of steps/statements. • Step n cannot be started until step n-1 is complete. CSCE 106

  5. General Form of a C++ Program // File: filename // Program description: …. #include directives using namespace std; void main() { Variables declaration section Executable statements section } CSCE 106

  6. General Form of a C++ Program (cont’d) • Function (a collection of related statements) is the basic unit in C++ • A C++ program must contain a main function void main () • void - function returns no value • main - lower case followed by () • { } - braces define the function body CSCE 106

  7. General Form of a C++ Program (cont’d) • General form of function body parts • Declaration statements • Variables and constants • Executable statements • C++ statements CSCE 106

  8. Comments • Comments make a program easier to understand • They are ignored (i.e. not translated) by the compiler • // used to signify a comment on a single line • /* Text text */ used for commentson multiplelines CSCE 106

  9. Compiler Directives • #include • Compiler directive • Processed during compilation process • Instructs on what you want in the program • #include <iostream> • Adds library class/file called iostream to program • Used with < > • Also “ “ user defined CSCE 106

  10. Program Processing Diagram CSCE 106

  11. Program Processing Diagram (2) CSCE 106

  12. <iostream> Included in iostream • cout refers to the standard output device; i.e. the screen cout << "Hello!"; • << output operator (insertion operator) • cin refers to the standard input device; i.e. the keyboard cin >> N1 >> N2; • >> input operator (extraction operator) directs input to variable CSCE 106

  13. Executable Statements • cout displays output on the screen cout << “Enter the distance in miles: ”; • cin gets input from the keyboard cin >> miles; • Assignment kms = KM_PER_MILES * miles; CSCE 106

  14. Reserved Words and Symbols • Reserved words have special meanings • Can NOT be used for other purposes (const, float and void are some examples) • Special symbols / delimiters • C++ has rules for special symbols = * ; { } ( ) // << >> [ ] , + - CSCE 106

  15. Data Types • Predefined data types • int (integer) • Positive or negative whole number • 1000 12 199 100000 • The size of an int depends on the machine and the compiler. On a PC it is usually a word (16 bits). • Other integers types are: • short: uses less bits (usually a byte) • long: typically uses more bits (usually 2 words) CSCE 106

  16. Data Types (cont’d) • float (floating point / real number) • Positive or negative decimal number • 10.5 1.2 100.02 99.88 • Integer part and fraction part • The number108.1517 breaks down into the following parts • 108 - integer part • 1517 - fractional part • Other floating-point data types are: • double • long double • bool (boolean) • true • false CSCE 106

  17. Data Types (cont’d) • char (character) • Represents a character • Individual character value (letter or number) • Character literal enclosed in single quotes ‘A’ • Characters are encoded using a scheme where an integer represents a particular character CSCE 106

  18. Exercise • Problem Analyse, design (using a flow chart), and implement (using C++) an algorithm that calculates, and outputs the sum (sum) of three numbers (n1, n2 & n3) input by the user. • Analysis • Input float n1: first variable float n2: second variable float n3: third variable • Output float sum: sum of n1, n2, & n3 CSCE 106

  19. Implementation (C++) #include <iostream> using namespace std; void main () { float n1, n2, n3, sum; cout << “Please input three numbers”; cin >> n1 >> n2 >> n3; sum = n1 + n2 +n3; cout << “The sum is” << sum; } Exercise (cont’d) START • Design Processing INPUT n1, n2, n3 sum = n1 + n2 + n3 OUTPUT sum STOP CSCE 106

  20. Addition.cpp /* FILE: Addition.cpp PROGRAM: Adds three numbers input by the user */ #include <iostream> using namespace std; void main () { float n1, n2, n3, sum; // declaring variables cout << “Please input three numbers”; cin >> n1 >> n2 >> n3; // inputting 3 variables sum = n1 + n2 + n3; // adding the 3 variables cout << “The sum is:” << sum; // outputting sum } CSCE 106

  21. Next lecture will be about Arithmetic Expressions CSCE 106

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