CPS120: Introduction to Computer Science

Introduction to C++

A Simple C++ Program

Comments // Simple C++ Program // // Purpose: To demonstrate the // parts of a simple C++ program

Compiler Directive #include <iostream.h>Main Function main ( )Braces {Statements cout << "This is a simple program ";

return 0;}

C++ and Blank Space

• C++ allows for great flexibility in the spacing and layout of code

• Use this feature to make it easier for you as a human being to read the code

Formatting in C++• Modern programming languages are free form with

delimiters instead of columns to determine the end of instructions

–The ; (semi-colon) is the delimiter used in C++

• Use tabs, indents, and blank lines in any manner that makes code easier to understand

• Many programming instructions become subordinate to other instructions due to scope and other restrictions. Formatting code to reflect this makes it easier to read

Uppercase or Lowercase

• Be careful to use the same combination of uppercase or lowercase lettering when you enter source code

• Commands and other reserved words are all lower case

Characteristics of a C++ Program

• Comments

• Compiler Directives

• Functions

• Braces

• Statements

Comments

• Explain the purpose of a program

• Keep notes regarding changes to source code

• Store details about the programmers for future reference

• Explain parts of the program

Comments

• Document what is happening, why it is happening and other issues

• Commentary is ignored by the compiler• C++ has inline, block and documentary comments

–Inline comments are within line of code• Use the // symbols

–Block comments are long comments delimited with /* and */

Sample CommentsAt the start of the program

/**************************************************

** Miles Per Gallon **

** Programmer: Paul J. Millis **

** Purpose: Calculate mile per gallon and price per mile **

** given miles, gallons and gas price **

*************************************************/Within specific lines of code

float PricePerMile = 0.00; //store the price per mile

float MilesPerGallon = 0.0; //stores the miler per gallon achieved

Compiler Directives

• Instructions to the compiler rather than part of the C++ language– Most common directive is #include

• For Example: #include <iostream.h>– A .h file is a header file. It serves as a link between

program code and standard C++ code needed to make programs run

Functions

• A function is a block of code that carries out a specific task

• Every C++ program has a main function that executes when a program initiates– Includes open parenthesis to designate a

function– Ends with a return 0; statement

Braces

• Mark the beginning and ending of blocks of related code– Every opening brace must have a closing brace

Statements

• Functions contain statements that consist of instructions or commands that make the program work

Semicolons

• There must be a semicolon after every statement– To tell the compiler that the statement is

complete– Function definitions and compiler directives are

exempt