1 1 14 Basics of a Typical C

2 1. 14 Basics of a Typical C++ Environment Phases of C++ Programs: 1. Edit 2. Preprocess 3. Compile Editor Preprocessor Compiler Linker 4. Link Loader 5. Load Disk 6. Execute Disk Program is created in the editor and stored on disk. Disk Preprocessor program processes the code. Disk Compiler creates object code and stores it on disk. Disk Primary Memory Loader puts program in memory. . . . Primary Memory CPU . . . 2003 Prentice Hall, Inc. All rights reserved. Linker links the object code with the libraries, creates a. out and stores it on disk CPU takes each instruction and executes it, possibly storing new data values as the program executes.

3 1. 14 Basics of a Typical C++ Environment • Input/output – cin • Standard input stream • Normally keyboard – cout • Standard output stream • Normally computer screen – cerr • Standard error stream • Display error messages 2003 Prentice Hall, Inc. All rights reserved.

1. 21 A Simple Program: Printing a Line of Text • Comments – – Document programs Improve program readability Ignored by compiler Single-line comment • Begin with // • Preprocessor directives – Processed by preprocessor before compiling – Begin with # 2003 Prentice Hall, Inc. All rights reserved. 4

1 2 3 // Fig. 1. 2: fig 01_02. cpp // A first program in C++. Function main returns an #include <iostream> 4 5 6 7 8 // function main int main() { std: : cout << "Welcome to C++!n"; 9 10 11 12 Outline Single-line comments. Preprocessor directive to integer value. Left brace { begins function include input/output stream begins execution Function main appears body. program Statements end with a header file <iostream>. exactly once in every C++ semicolon ; . program. . return 0; // } // end function Welcome to C++! Corresponding right brace } indicate that program ended successfully ends function body. Stream insertion operator. Name cout belongs to main namespace std. Keyword return is one of several means to exit function; value 0 indicates program terminated successfully. fig 01_02. cpp (1 of 1) fig 01_02. cpp output (1 of 1) 2003 Prentice Hall, Inc. All rights reserved. 5

1. 21 A Simple Program: Printing a Line of Text • Standard output stream object – std: : cout – “Connected” to screen – << • Stream insertion operator • Value to right (right operand) inserted into output stream • Namespace – std: : specifies using name that belongs to “namespace” std – std: : removed through use of using statements • Escape characters – – Indicates “special” character output 2003 Prentice Hall, Inc. All rights reserved. 6

1. 21 A Simple Program: Printing a Line of Text 2003 Prentice Hall, Inc.

1 2 3 // Fig. 1. 4: fig 01_04. cpp // Printing a line with multiple statements. #include <iostream> 4 5 6 7 8 9 // function main begins program execution int main() { std: : cout << "Welcome "; std: : cout << "to C++!n"; 10 11 12 13 return 0; Multiple stream insertion statements produce one line of output. // indicate that program ended successfully } // end function main Welcome to C++! Outline fig 01_04. cpp (1 of 1) fig 01_04. cpp output (1 of 1) 2003 Prentice Hall, Inc. All rights reserved. 8

1 2 3 // Fig. 1. 5: fig 01_05. cpp // Printing multiple lines with a single statement #include <iostream> 4 5 6 7 8 // function main begins program execution Using newline characters to print on multiple lines. int main() { std: : cout << "Welcomentonn. C++!n"; 9 10 11 12 return 0; // indicate that program ended successfully } // end function main Welcome to C++! Outline fig 01_05. cpp (1 of 1) fig 01_05. cpp output (1 of 1) 2003 Prentice Hall, Inc. All rights reserved. 9

1. 22 Another Simple Program: Adding Two Integers • Variables – Location in memory where value can be stored – Common data types • int - integer numbers • char - characters • double - floating point numbers – Declare variables with name and data type before use integer 1; integer 2; int sum; – Can declare several variables of same type in one declaration • Comma-separated list integer 1, integer 2, sum; 2003 Prentice Hall, Inc. All rights reserved. 10

1. 22 Another Simple Program: Adding Two Integers • Variables – Variable names • Valid identifier – Series of characters (letters, digits, underscores) – Cannot begin with digit – Case sensitive 2003 Prentice Hall, Inc. All rights reserved. 11

1. 22 Another Simple Program: Adding Two Integers • Input stream object – >> (stream extraction operator) • Used with std: : cin • Waits for user to input value, then press Enter (Return) key • Stores value in variable to right of operator – Converts value to variable data type • = (assignment operator) – Assigns value to variable – Binary operator (two operands) – Example: sum = variable 1 + variable 2; 2003 Prentice Hall, Inc. All rights reserved. 12

1 2 3 // Fig. 1. 6: fig 01_06. cpp // Addition program. #include <iostream> 4 5 6 7 8 9 10 // function main begins program execution int main() Declare integer variables. { integer 1; // first number to be input by user integer 2; // second number to be input by user Use stream extraction operator int sum; // variable in which sum will be stored Outline with standard input stream to obtain user input. integern"; // prompt 11 12 13 std: : cout << "Enter first std: : cin >> integer 1; 14 15 16 std: : cout << "Enter second integern" ; // prompt std: : cin >> integer 2; // read an integer Calculations can be performed in output statements: alternative for // read an integer 17 18 sum = integer 1 + integer 2; 19 20 std: : cout << "Sum is " << sum << std: : endl; // print 21 22 return 0; 23 24 lines 18 and 20: // assign result to sum fig 01_06. cpp (1 of 1) Stream manipulator std: : endl outputs a newline, then “flushes output integer 1 + integer 2 << std: : endl; sum buffer. ” // indicate that program ended successfully } // end function main Concatenating, chaining or cascading stream insertion operations. 2003 Prentice Hall, Inc. All rights reserved. 13

Enter first integer 45 Enter second integer 72 Sum is 117 Outline fig 01_06.

15 1. 23 Memory Concepts • Variable names – Correspond to actual locations in computer's memory – Every variable has name, type, size and value – When new value placed into variable, overwrites previous value – Reading variables from memory nondestructive 2003 Prentice Hall, Inc. All rights reserved.

16 1. 23 Memory Concepts std: : cin >> integer 1; integer 1 45 std: : cin >> integer 2; integer 1 45 – Assume user entered 72 integer 2 72 integer 1 45 integer 2 72 – Assume user entered 45 sum = integer 1 + integer 2; sum 2003 Prentice Hall, Inc. All rights reserved. 117

17 1. 24 Arithmetic • Arithmetic calculations – * • Multiplication – / • Division • Integer division truncates remainder – 7 / 5 evaluates to 1 – % • Modulus operator returns remainder – 7 % 5 evaluates to 2 2003 Prentice Hall, Inc. All rights reserved.

18 1. 24 Arithmetic • Rules of operator precedence – Operators in parentheses evaluated first • Nested/embedded parentheses – Operators in innermost pair first – Multiplication, division, modulus applied next • Operators applied from left to right – Addition, subtraction applied last • Operators applied from left to right 2003 Prentice Hall, Inc. All rights reserved.

1. 25 Decision Making: Equality and Relational Operators • if structure – Make decision based on truth or falsity of condition • If condition met, body executed • Else, body not executed • Equality and relational operators – Equality operators • Same level of precedence – Relational operators • Same level of precedence – Associate left to right 2003 Prentice Hall, Inc. All rights reserved. 19

1. 25 Decision Making: Equality and Relational Operators 2003 Prentice Hall, Inc. All rights

1. 25 Decision Making: Equality and Relational Operators • using statements – Eliminate use

1 2 3 4 // Fig. 1. 14: fig 01_14. cpp // Using if statements, relational // operators, and equality operators. #include <iostream> 5 6 7 8 using std: : cout; using std: : cin; using std: : endl; 9 10 11 12 13 14 // function main begins program. Declare variables. execution int main() { Can write cout and cin int num 1; // first number to be read from user without std: : prefix. int num 2; // second number to be read from user // program uses cout // program uses cin // program uses endl Outline using statements eliminate need for std: : prefix. 15 16 17 18 cout << "Enter two integers, and I will tell youn" if structure compares values << "the relationships they satisfy: " ; of num 1 and num 2 to test for If condition is true (i. e. , values cin >> num 1 >> num 2; // read two integers 19 20 21 if ( num 1 == num 2 ) cout << num 1 << " is 22 23 24 if ( num 1 != num 2 ) cout << num 1 << " is not equal to " << num 2 << endl; fig 01_14. cpp (1 of 2) equality. are equal), execute this if structure compares values statement. of num 1 and num 2 to test for If condition is true (i. e. , values equal to " << num 2 << endl; are not equal), execute this inequality. statement. 25 2003 Prentice Hall, Inc. All rights reserved. 22

26 27 if ( num 1 < num 2 ) cout << num 1 << " is less than " << num 2 << endl; 28 29 30 if ( num 1 > num 2 ) cout << num 1 << " is greater than " << num 2 << endl; 31 32 33 34 if ( num 1 <= num 2 ) cout << num 1 << " is less than or equal to " << num 2 << endl; 35 36 37 38 if ( num 1 >= num 2 ) cout << num 1 << " is greater than or equal to " << num 2 << endl; fig 01_14. cpp (2 of 2) 39 40 return 0; fig 01_14. cpp output (1 of 2) 41 42 // indicate that program ended successfully Outline 23 Statements may be split over several lines. } // end function main Enter two integers, and I will tell you the relationships they satisfy: 22 12 22 is not equal to 12 22 is greater than or equal to 12 2003 Prentice Hall, Inc. All rights reserved.

Enter two integers, and I will tell you the relationships they satisfy: 7 7 7 is equal to 7 7 is less than or equal to 7 7 is greater than or equal to 7 Outline fig 01_14. cpp output (2 of 2) 2003 Prentice Hall, Inc. All rights reserved. 24