Overview of Programming Language Features

1. 3 Overview of ProgrammingLanguage Features AIM To develop further an understanding of the transition from the design phase to the program development phase OBJECTIVES • Study languages in general, and programming languages in particular • Study the relationship between design notation and the facilities that mirror this in a modern programming language V6.0

2. Languages: In General Terms 3.1 • All languages are subject to a set of rules governing • the set of valid characters that can be used • word construction • sentence construction • The rules of sentence construction are called syntax • To use a language correctly you need to know about these and • vocabulary - the set of valid words • semantics - ensuring that what is written makes sense • You need to be able to recognize language 'tokens'

3. Syntax Rules • English language descriptions of language rules can be very cumbersome, and lead to ambiguity • Syntax diagrams are a neat way of expressing language rules • they should be completely unambiguous • they usually involve other syntactic elements (tokens) • What would a syntax diagram look like for • a word • a sentence • prose Lesson: The ability to read a syntax diagram is an important skill.

4. Syntax vs. Semantics Syntax - the grammatical arrangement of words to show their connection and relation; the set of rules governing this arrangement. Semantics - relate to meaning in language • A sentence in English may be syntactically correct • it obeys the language rules • But not necessarily semantically correct • it has no valid meaning • Both syntax and semantics are important Lesson: You’ve got to put the syntactic elements together so that they are both syntactically and semantically correct.

5. Programming Language Building Blocks 3.2 • A computer program is like a set of instructions • Each instruction is termed a statement • Each program statement has a terminating character • Translate into syntax diagrams

6. Types Of Statement • It’s useful to categorize statements • type definitions - introduce new types • variable declarations - introduce new objects • assignment statements - involve a change in the value of an object • I/O statements • compound statements - a (bracketed) collection of statements • control-flow statements - change the normal linear flow of control (selection, repetition, function) • other forms of statement

7. 4 Starting C++Programming AIM To get started on programming in C++ OBJECTIVES • Understand the Systems Development Life Cycle (SDLC) • Simple C++ statements • Program layout and style • Simple input and output in C++ • Comments in C++ V6.0

8. Display a Greeting #include <iostream.h> int main() { cout << "Hello "; cout << "Your name" << endl; cout << "Welcome to MIS442" << endl; return 0; } PROBLEM: DESIGN: Hello Display “Hello” Display your name Display “Welcome to MIS442” End IMPLEMENTATION: Chapter 4 Hello 4.0 A First C++ Program Lesson: Try things out in small test programs to determine what C++ features do.

9. 4.1 Structure Of Simple C++ Programs • See syntax diagram simple C++ program • We’ll gradually introduce the different forms of statement that you can write in C++ • The cout "..." ...; lines in the greeting program are statements that produce output • Special significance of main() and the braces { and } • Your programs must conform to the syntax rules of the language, as specified in the syntactic elements • The syntax rules allow the computer to distinguish between syntactically correct and syntactically incorrect programs • But what if a program doesn't conform?

10. Object Code C++ Source #include ".. int main() { ... ... } // end main() C++ Compiler Compiler Error Messages Error: line 8 ... C++ Compile-Time Errors • What if you make a syntax mistake in your source program? Lesson: A single syntax error may give rise to multiple compiler error messages. Lesson: You’ll have to get used to the form of the compiler’s error messages. Lesson: It may be worth fixing the first source-code error and then recompiling.

11. 4.2 Program Layout And Style • Are either of these C++ fragments syntactically legal? int main(){cout<<"Hello" ;cout<<"Yourname"<<endl ;cout<<"Welcome to MIS442" <<endl;return0;} À int main(){cout<<"Hello" ;cout<<"Yourname"<<endl ;cout<<"Welcome to MIS442" <<endl; return 0;} Á Lesson: The aesthetics of your program’s appearance to the human eye are very important. Lesson: Adopt sensible style rules and stick with them.

12. Overall Layout Of C++ Programs • C++ is a free-format language • The compiler ignores white space (spaces, tabs, end of line, blank lines) in most situations #include <iostream.h> int main() { cout << "Hello "; cout << "Your name" << endl; cout << "Welcome to MIS442" << endl; return 0; } • Use indentation and white space to make your programs more readable. The compiler doesn’t care about white space.

13. 4.3 Simple I/O In C++ Design and write a program that asks a user to input their first name followed by their age in years, and then calculates and prints their age in hours. PROBLEM: DESIGN:

14. I/O In C++ (Conti.) #include <iostream.h> #include <cstring.h> cin >> cout << getline(cin, variable, ‘\n’); #include <iomanip.h> cout.setf(ios::showpoint); cout.setf(ios::fixed); cout.setf(ios::right); cout.precision(2) cout << ... << setw(9) << ... ;

15. 4.4 Comments • Program statements alone are often not very readable • Often you wish to add some commentary to a program • Such comments give the reader additional information • There has to be a syntactic element in the language to permit this – see comment

16. + // Source file name: hello.c // A C++ program to print out a greeting message // Edit the lines indicated below // Include the information which defines the IO types #include <iostream.h> int main() { cout << "Hello "; cout << "Your name" // Edit to your name << endl; cout << "Welcome to MIS442" // Edit to your course << endl; return 0; } // end main() + + + 4.4 Comments

17. Chapter 4 Program Template Comments: Style Rules • A program without any comments is a bad program. • A comment should add something to the program. • And not just expand on the obvious. • Add comments while you are implementing your program. • Capture design abstractions as comments in the source code. • Use white space to improve their readability. • A source file should identify the name and purpose of the program, and its author and date. • Use a template for new programs.

18. 4.5 Systems /Software Development Life Cycle (SLC/ SDLC) • A method that provides information systems professionals with step-by-step procedures to develop their projects/systems. • SOFTWARE ENGINEERING ...

19. 1. (Problem) Conceptualization • Prepare a complete and unambiguous problem statement. • Users and analysts sign the requirements document.

20. 2. Analysis • Understand the problem: develop a system behavior model and determine problem input, output, and other relevant data elements. • Name each identified data element and develop a model of the essential characteristics (attributes and operations) for each element.

21. 3. Design • Using the system and data models developed during requirements analysis, perform a top-down design of the system. • For each system component, identify key data elements and subordinate functions using structure charts.

22. 4. Implementation • Write algorithms and pseudocode descriptions of individual functions. • Code the solution. • Debug the code.

23. 5. Testing and Verification • Test the code, verifying that it is correct. Each data modeling component should be tested separately, before all components are tested as an integrated whole. • Involve users and special testing teams in all system tests.

24. 6. Operation, Follow-up, and Maintenance • Run the completed system. • Evaluate its performance. • Remove new bugs as they are detected. • Make required changes to keep the system up to date. • Verify that changes are correct and that they do not adversely affect the system’s operation.

25. Summary Your first steps as a C++ programmer: • Use of syntax diagrams • Compile-time errors • Basic structure of simple C++ programs • Simple I/O in C++ • C++ comments Your first steps as a software engineer: • Program layout and white space • Style rules • Use of comments to capture the design • Constructing test programs to see what C++ features do

26. More C++ Examples • miles.cpp (p. 40) • Hello.cpp (p.55) • A Case Study: Finding The Value of A Coin Collection: Coins.cpp (p.82)

27. End

28. Sieve Program IMPLEMENTATION: Chapter 3 Sieve OUTPUT:

29. Summary • You now know about the importance of syntax and semantics • You know how to read syntax diagrams • You know about the basic features of programming languages • You should be able to recognize these features in many popular languages (especially C++) • But you don't know enough yet to be able to write programs ...

30. variable names #include <iostream.h> #include "Text.h" int main() { const double HOURS_YEAR = 365.0 * 24.0; int age; Text name; cout << "What is your first name? "; cin >> name; cout << "and what is your age in years? "; cin >> age; cout << "Welcome to " << name << " who claims to be " << (age * HOURS_YEAR) << " hours young" << endl; return 0; } constant declaration variable declarations expression input statements Age-In-Hours Program IMPLEMENTATION:

31. Age-In-Hours Program OUTPUT:

32. Drawing A Square Design and implement a program to draw a square. int main() { // Create window and sideLength // Input a value for sideLength // Move to starting position // Put the pen down // Draw line forward // Draw line up // Draw line back // Draw line down return 0; //exit the program } //end main() PROBLEM: DESIGN: IMPLEMENTATION: Lesson: A useful starting point is a set of comments expressing the design.