Notes

Outline

The Elements of C++ Programs In C ++, all subprograms are called functions. Every C program must have a function named main. Other functions are called by main. Program execution returns to main when the callee function completes execution.

Example C++ Program #include <iostream> using namespace std; int Square(int); int Cube(int); int main() { cout << “The square of 27 is” << Square(27) << endl; cout << “and the cube of 27 is” << Cube(27) << endl; return 0; }

Example C++ Program (continued) int Square(int n) { return n*n; } int Cube(int n) { return n*n*n; } The left brace({) and right brace (}) mark the beginning and end of the statements to be executed.

Notes on Program Execution The first statement in main is cout << The square of 27 is” << Square(27) << endl; During the execution of this statement, Square is called, returning a value of 729, which is printed out, followed by a new line character. Then, the statement cout << “and the cube of 27 is” << Cube(27) << endl; is executed which includes a call of Cube. The value 19683 (the cube of 27) is displayed. Both Square and Cube are examples of value-returning functions, i.e. int Square(int n). main is also a value-returning function, 0 usually indicates normal (error-free) execution has occurred. main is called by the operating system.

Example C++ Program #include <iostream> using namespace std; int Square(int); int Cube(int); int main() { cout << “The square of 27 is” << Square(27) << endl; cout << “and the cube of 27 is” << Cube(27) << endl; return 0; }

Example C++ Program (continued) int Square(int n) { return n*n; } int Cube(int n) { return n*n*n; }

Example C++ Program #include <iostream> using namespace std; int Square(int); int Cube(int); int main() { cout << “The square of 27 is” << Square(27) << endl; cout << “and the cube of 27 is” << Cube(27) << endl; return 0; }

Example C++ Program (continued) int Square(int n) { return n*n; } int Cube(int n) { return n*n*n; }

Example C++ Program #include <iostream> using namespace std; int Square(int); int Cube(int); int main() { cout << “The square of 27 is” << Square(27) << endl; cout << “and the cube of 27 is” << Cube(27) << endl; return 0; }

Example C++ Program (continued) int Square(int n) { return n*n; } int Cube(int n) { return n*n*n; }

Example C++ Program #include <iostream> using namespace std; int Square(int); int Cube(int); int main() { cout << “The square of 27 is” << Square(27) << endl; cout << “and the cube of 27 is” << Cube(27) << endl; return 0; }

Example C++ Program (continued) int Square(int n) { return n*n; } int Cube(int n) { return n*n*n; }

Example C++ Program #include <iostream> using namespace std; int Square(int); int Cube(int); int main() { cout << “The square of 27 is” << Square(27) << endl; cout << “and the cube of 27 is” << Cube(27) << endl; return 0; }

Example C++ Program (continued) int Square(int n) { return n*n; } int Cube(int n) { return n*n*n; }

Example C++ Program #include <iostream> using namespace std; int Square(int); int Cube(int); int main() { cout << “The square of 27 is” << Square(27) << endl; cout << “and the cube of 27 is” << Cube(27) << endl; return 0; }

Example C++ Program (continued) int Square(int n) { return n*n; } int Cube(int n) { return n*n*n; }

Example C++ Program #include <iostream> using namespace std; int Square(int); int Cube(int); int main() { cout << “The square of 27 is” << Square(27) << endl; cout << “and the cube of 27 is” << Cube(27) << endl; return 0; }

Example C++ Program (continued) int Square(int n) { return n*n; } int Cube(int n) { return n*n*n; }

Example C++ Program #include <iostream> using namespace std; int Square(int); int Cube(int); int main() { cout << “The square of 27 is” << Square(27) << endl; cout << “and the cube of 27 is” << Cube(27) << endl; return 0; }

Example C++ Program (continued) int Square(int n) { return n*n; } int Cube(int n) { return n*n*n; }

Syntax and Semantics Syntax consists of the formal rules governing how valid instructions are written in a programming language. (grammar) Semantics consists of the set of rules that determines the meaning of instructions written in a programming language. (meaning) A metalanguage is a language that is used to write the syntax rules for another language. In this book, we write the syntax rules for C++ using a metalanguage called a syntax template.

Syntax Templates A syntax template is a generic example of the C++ construct being defined. Graphic conventions show which portions are optional and which can be repeated. A boldface word or symbol is a literal word or symbol in the  C++ language. A nonboldface word can be replaced by another template. A curly brace is used to indicate a list of items, from which one item can be chosen. Shading indicates an optional part of the definition.

Syntax Template Example Identifier Letter Digit

Naming Program Elements Identifiers are used in C++ to name things – identifiers are made up of letters, digits, and the underscore character (_), and must begin with a letter or an underscore. Valid identifiers Invalid identifiers sum_of_squares 40hours J9 Get Data box_22A box-22 GetData cost_in_$ Bin3D4 int count

Data and Data Types A data type is a specific set of data values, along with a set of operations on those values. Data is stored in the computer’s memory. Data is like post office boxes, some are larger than others. Two data types for now: The char Data Type – describes data consisting of one alphanumeric character. We enclose them in single quotation marks, e.g., ‘A’ ‘a’ ‘_’ ‘8’ The string Data Type – describes data consisting of a sequence of characters. We enclose them in double quotation marks, e.g., “Hello” “My name is Rhonda”

Naming Elements: Declaration A declaration tells the computer what an identifier represents. (object, function, or type) In C++, you must declare every identifier before it is used. A memory location which can change is known by a variable name. VariableDeclaration DataType Identifer , Identifier …; A memory location(s) whose value never changes is known by a constant name ConstantDeclaration const DataType Identifier = LiteralValue;

Declaration Examples Variables char letter, middleInitial, ch; float payRate; // Employee’s pay rate float hours; // Hours worked Constants const string STARS = “*********”; const char BLANK = ‘ ’; const string BOOK_TITLE = “Programming and Problem Solving with C++”; const string MESSAGE = “Error Condition”;

Matters of Style Warning: C++ is case-sensitive – Style and style are not the same Capitalization Conventions Identifiers representing variables begin with a lower-case letter and have each successive English word capitalized, e.g., lengthInYards Names of programmer-written functions and program-mer-defined data types begin with capital letters and have each successive English word capitalized, e.g., CalcPay(payRate, hours, wages) Identifiers representing constants are all capitals, with words separated by underscores, e.g., MAX_LENGTH

Executable Statements The value of a variable can be set or changed through an assignment statement, e.g., lastName = “Lincoln”; AssignmentStatement Variable = Expression; An expression is an arrangement of identifiers, literals, and operators that can be evaluated to compute a value of a given type.

Valid and Invalid Assignments Given the declarations string firstName; char middleInitial; string middleName; char letter; string lastName; string title; Valid Assignments Invalid Assignments firstName = “Abraham”; middleInitial = “A.”; middleName = firstName; letter = firstName; middleName = “ ”; firstName = Thomas; lastName = “Lincoln”; “Edison” = lastName; title = “President”; lastName = ; middleInitial = ‘ ’; letter = middleInitial;