First C++ Program

• C++ facilitates a disciplined approach to program development.
• The programs process data and display results.

First C++ Program

• It prints a line of text.
• // indicates the remainder of each line is a comment, documenting the program for readability and understanding.
• Comments are ignored by the C++ compiler.
• Comments can either be initiated with // for a single-line comment or enclosed within /* and */ for multi-line comments.
• A preprocessing directive is a message to the C++ preprocessor.
• Lines starting with # are handled by the preprocessor before compilation.
• #include <iostream> directs the preprocessor to include the input/output stream header file <iostream>.
  • This header file is essential for programs that output data to the screen or receive input from the keyboard using C++ stream input/output.
• Blank lines, spaces, and tabs enhance program readability and are collectively known as white space.
  • The compiler generally ignores white-space characters.
• main is a fundamental part of every C++ program, serving as a program-building function.
• Programs consist of functions and classes, with the requirement of having one main function.
• Execution of C++ programs starts at the main function, irrespective of its position in the code.
• The keyword int preceding main specifies that main yields an integer value.
  • A keyword is a reserved term in C++ with a specific function.
• A left brace {marks the beginning of every function's body.
• A corresponding right brace } concludes its body.
• A statement is an instruction that directs the computer to perform an action.
• Combined quotation marks and the enclosed characters constitute a string, character string, or string literal.
• Characters within double quotation marks are considered strings.
  • White-space characters in strings are not filtered out by the compiler.
• Most C++ statements terminate with a semicolon ;, identified as the statement terminator.
  • Preprocessing directives like #include do not require a semicolon.
• Output and input operations leverage streams of data.
• A cout command directs a series of characters toward the standardized output pathway, std::cout, typically linked to the display screen.
• The specification of std:: before the cout command is necessary when utilizing components incorporated by preprocessing directive #include.
  • Notation of std::cout implies using an entity, cout, as an element of namespace std.
  • The names cin and cerr also are part of the "namespace" std.
• Escape sequences represent characters that are difficult or impossible to represent directly in code.
• The stream insertion operator, denoted as \<\<, is used in output statements to insert values into the output stream.
  • The value on the right side of the operator, known as the operand, is inserted into the output stream.
• The characters specified by \n do not appear on the screen directly; instead, they represent a newline.
• The backslash \ serves as an escape character, signaling that a special character is to be outputted.
  • When encountered within a character sequence, the backslash combines with the subsequent character to create an escape sequence.
• The escape sequence \n has a "newline" effect, advancing the cursor to the next line on the display.
• The return statement, when positioned at the conclusion of main, the value 0 signifies the program's successful completion.
• Omitting the return statement in the main function, the program assumes it terminated successfully.

Modifying the First C++ Program

• Printing "Welcome to C++!" can be achieved in various ways.
• A single command is capable of indicating different lines through the implementation of newline characters.
• The newline character \n encountered in the output stream shifts the screen cursor to the beginning of the subsequent line.
• Including two successive newline characters creates a blank line in the output.

Another C++ Program

• It adds Integers.
• Declarations introduce identifiers.
• The identifiers number1, number2 and sum are the names of variables.
• A variable is a location in the computer's memory where a value can be stored for use by a program.
• The variables such as number1, number2 and sum are data of int type in the memory.
  • It means that these variables will hold integers (whole numbers such as 7, -11, 0 and 31914).
• Lines 8-10 initialize each variable to 0 by placing a value in braces ({ and }) immediately following the variable's name
  • This initialization method is called list initialization, which was introduced in C++11.
• All variables must have a specified name and data type before utilization in a program.
• Multiple variable names can be declared in a single declaration separated by commas, termed a comma-separated list.
• double data type specifies numbers with decimal points.
• char data type specifies a single character data.
• Int, double and charare fundamental types.
• Variable names need to adhere to identifier naming protocols and cannot match any keyword.
• A variable name that qualifies as a valid identifier cannot be a keyword.
• Identifiers are sequences comprising letters, digits, and underscores (_), on the condition that they do not commence with a digit.
• C++ distinguishes between uppercase and lowercase letters.
  • Resulting in a1 and A1 being regarded as distinct variable identifiers.
• Variable declarations can be located anywhere within the scope of its program’s code.
  • However variables must be declared before their usage.
• A prompt is used to guide the user to do something in particular.
• A cin statement uses the input stream object cin which is of namespace std and stream extraction operator, >> to gather a value from the keyboard.