CS 2400 OHIO U Quiz 1 (1/29/21)

Include directives

#include <iostream> #include <cstdlib> • Tells the compiler to find information about certain items in your program

C++ Program Structure

#include <iostream> using namespace std; int main() { variable declaration Statement_1 Statement_2 ... Last statement return 0; // EXIT_SUCCESS // #include <cstdlib> }

compile-time error

A compile-time error is a violation of the programming language rules that is detected by the compiler.

C++

C developed by Dennis Ritchie at AT&T Bell Labs in the 1970s. - Used to maintain UNIX systems - Many commercial applications written in c • C++ developed by Bjarne Stroustrup at AT&T Bell Labs in the 1980s. - Overcame several shortcomings of C - Incorporated object-oriented programming - C remains a subset of C++

What output is generated by the statements below? cout << "C++"; cout << " is " << endl; cout << "fun";

C++ is fun

Editing Your Program

Create the program in a text file with any of the following extensions: cc, cpp, cxx

Which of the following programs are not typically written in C++?

Web applications

Swap Variable Content

int num1 = 5, num2 = 6;

Program Style

• A program written with attention to style - is easier to read - easier to debug - easier to maintain

Alternative Formatting Method

• Alternatively, we can use: - cout.setf(ios::fixed); - These flags can also be combined in one cout.setf statement ocout.setf(ios::left | ios::fixed);

Strings

• Strings (#include <string>) - string: A group of characters. - string constants are surrounded by double quotes: "Hello World"

Program Errors

• Syntax errors - Violation of the grammar rules of the language - Discovered by the compiler o Error messages may not always show correct location of errors • Run-time errors - Error conditions detected by the computer at runtime • Logic errors - Errors in the program's algorithm - Most difficult to diagnose - Computer does not recognize an error

Running Your Program

• To run the program - ./a.out (Mac, Linux) - ./a.exe (Windows)

Variable Naming Convention

• Use all small letters - first, second • Use one of the following naming conventions if the variable name has multiple words - firstBank, firstLocalBank - first_bank, first_local_bank

Namespace

• using namespace std; Interpret iostream in a standard way. Without this line you have to enter - std::cout

Hardware Components

- CPU (Central Processing Unit) - Main Memory - Secondary Memory - Input Devices - Output Devices

Introduction Cont. (Large amounts of memory is measured in)

- Kilobyte (KB) = 103 = 1,000 bytes - Megabyte (MB) = 106 = 1,000,000 bytes - Gigabyte (GB) = 109 = 1,000,000,000 bytes - Terabyte (TB) = 1012 = 1,000,000,000,000 bytes

Introduction Cont. (Memory)

- Measured in bytes - A byte is 8 bits - a bit is the smallest unit of storage. A bit represents the binary digits 0 and 1. - Each byte has an address (A sequence of bytes are identified by the address of the first byte.) - A word is 2, 4, or 8 bytes depending on the system

Software

- Operating System (Windows, Mac OS, Linux, iOS etc.) - Applications (Chrome, Office products, C++ Compiler, Spreadsheets, GNU C++)

Introduction Cont. (Example calculating 5+6)

- What is involved in calculation - input/output - How much memory is required? - Can it be done with one memory location? Why/Why not?

setw, Cont.

- cout << setw(9) << "Hello"; // prints ¨¨¨¨Hello - cout << setw(2) << "hello"; • If the width value specified is not big enough, it will be ignored

Mixing Expressions

- long double -> most dominant type - double - float - long long - long int - int - short - char -> least dominant type

Math Functions Examples

- root = sqrt(16); will assign 4.0 to the variable root. sqrt function returns a double value - result = pow(2, 3); returns 23 oassigns the double value 8.0 to result. - log(x) returns ln x - log10(x) returns log10 x - Trigonometric functions: sin, cos, tan, etc. - abs returns the absolute value of an integer - fabs returns the absolute value of a float

Documentations/Comments

/** * @file: introProgram.cpp * @author: Nasseef Abukamail * * @date: August 28, 2019 * @brief: * A program that reads two integers and does simple * arithmetic calculations. */ To comment a single line use //

Which of the following statements is true about a compiler?

A C++ programmer using a compiler doesn't need to know machine instructions.

run-time error

A run-time error causes a program to take an action that the programmer did not intend.

Which of the following is not an advantage of programming in a higher-level language instead of machine code?

Instructions do not need to be encoded before a program runs.

Which of the following statements is false?

The distinction between upper- and lowercase letters is unimportant in C++.

Type Casting (Conversion)

Used for explicit type conversion int iVar = 2; double dVar; dVar = static_cast (iVar); Converts iVar to double and assigns it to dVar char ch = 'B'; cout << static_cast (ch); Displays the ASCII value of ch (66)

Character Arithmetic

char ch = 'A'; // assigns 'A' to ch ch = ch + 2; // assigns 'C' to ch int distance = ch - 'A'; - How far is ch from the letter 'A' in the ASCII table?

Fixed vs. Scientific "precision"

double value = 123456789.12345; cout << "Value without formatting: " << value << endl; cout << setprecision(4); cout << "Value after precision of 4: " << value << endl; cout << fixed << "Value in fixed notation: " << value << endl; Output: Value without formatting: 1.23457e+08 Value after precision of 4: 1.235e+08 Value in fixed notation: 123456789.1235

When writing a C++ program, you type your code into a(n) ___ window.

editor

Main function

int main() { //start here return 0; } • The main function of the program. This defines the entry point of the program.

Shortcut Assignment

number = number + 4; à number += 4; number = number - 6; à number -= 6; number = number % 3; à number %= 3; number = number * (3 + 4); à number *= 3 + 4; // tricky

Integer Remainders

• % operator gives the remainder from integer division int dividend, divisor,remainder; dividend = 23; divisor = 5; remainder = dividend % divisor; The value of remainder is 3

Increment/Decrement

• ++ increment operator - Adds 1 to the value of a variable number++; or ++number; is equivalent to number = number + 1; • -- decrement operator - Subtracts 1 from the value of a variable number--; or --number; is equivalent to number = number - 1;

Expressions

• A constant value (2, -3.4, 'A') • A variable • A combination of variables, constants, and operators (+, -, /, *, %) • May contain parenthesis ( )

Programming Style

• Add spaces around operators • Break long statements into either multiple statements or multiple lines • Indent blocks for if, while, etc. if (x == 0){ statements; } • Adding blank lines between logical groups of statements

Algorithm

• Algorithm - A set of well defined logical steps to perform a task (leads to a solution) • Computer Program - Set of instructions for a computer to follow written in a programming language such as C++.

Software Life Cycle

• Analysis and specification • Design of the software (program) - Writing an algorithm o Define the input o Define the process (calculations) o Define the output

Arithmetic

• Arithmetic is performed with operators - + for addition - - for subtraction - * for multiplication - / for division - % remainder of division of integers (mod operator) 11 May 2020 CS2

Division of Integers

• Be careful with the division operator! - int / int produces an integer result (true for variables or numeric constants) int dividend, divisor, quotient; dividend = 5; divisor = 3; quotient = dividend / divisor; - The value of quotient is 1, not 1.666... - Integer division does not round the result, the fractional part is discarded!

Variable Initializations

• Before use, variables must be declared. • Variables may be initialized at the declaration. Otherwise, they will contain garbage. - int rank = 3; - string name = "John Smith"; • Multiple variables can be declared and initialized in one declaration statement int first = 3, second, third = 8; char middle = 'A';

Testing and Debugging

• Bug - A mistake in a program • Debugging - Eliminating mistakes in programs - Term used when a moth caused a failed relay on the Harvard Mark II computer. Grace Hopper and other programmers taped the moth in logbook stating: "First actual case of a bug being found."

Math Functions

• Built-in functions in expressions • Must include the library - #include § sqrt(x), abs(x), fabs(x), sin(x), cos(x), exp(x), log(x), log10(x), pow(b, p) • These functions return the calculated value

Default Format for Double

• C++ default format for double values is to display up to 6 digits. The number will be rounded accordingly. • Examples: - 30000.123 displays as 30000.1 - 300000.567 displays as 300001 - 3.123456 displays as 3.12346 - 30000000 displays as 3e+07

Data Types, Cont. (Characters and Boolean)

• Characters - char 1 byte - characters are surrounded by single quotes: 'A','6', '?', ' ', • Boolean - bool 1 byte o Has values of true or false

ASCII/Unicode Characters

• Characters have standard codes • These codes are called ASCII (American Standard Code for the Information Interchange) codes • Each ASCII code is 8 bits, see Appendix C • Unicode characters use 16-bit codes • Some codes - 'A' is 65 in decimal, 01000001 in binary - '1' is 49 in decimal, 0011001 in binary

Software Life Cycle, Cont.

• Coding/Implementation - Writing the algorithm in C++ - Correct syntax errors • Testing - Correcting logic errors - Correcting run-time errors • Maintenance and evaluation

Compiling

• Compile and Link using the command - g++ -Wall first.cc oThis creates an executable file called • a.out (Mac and linux) • a.exe (Windows) - g++ -Wall first.cc -o first oThis creates the executable • first (Mac and linux) • first.exe (Windows)

Security Objectives CIA Triad

• Confidentiality (or secrecy) - Information cannot be accessed by people who are not authorized to view/use it • Integrity - Unauthorized users cannot alter data and make it unreliable • Availability - Authorized users can always access information

Division of Doubles

• Division with at least one operand of type double produces the expected results. double divisor, dividend, quotient; divisor = 3; dividend = 5; quotient = dividend / divisor; - quotient = 1.6666...

Program Style - Indenting

• Document all programs. Include: - Author name - Date created/modified § Description of the program - Add documentations throughout the program - Always prompt the user for the input • The program output should be readable and clearly labeled.

Type Compatibilities

• In general store values in variables of the same type - This is a type mismatch: int intVar; intVar = 2.99; - intVar will contain the value 2. - You may get a warning

Data Types

• Integers (whole numbers): -4, 0, 100, etc. - int 4 bytes - short 2 bytes - long At least 4 bytes, 8 on 64-bit systems - long long At least 8 bytes - unsigned qualifier is used for positive integers only - Overflow/underflow

Programming Languages

• Machine Language - The only language the computer understands - Consists of series of binary codes - Difficult to program - 00100010111010001 • Assembly Language - ADD EAX, EBX • High level languages - C++, C, Java, Swift, .. - English-like - Easy to program - value = 5 + 6

Formatting Output

• Must #include • Specifying the width of the next output field - cout << setw(5) << 3; // prints ¨¨¨¨3 // 4 spaces followed by 3 - cout << setw(5) << 34; // prints ¨¨¨34

ASCII Codes Cont.

• Organization of the ASCII codes - All Capital letters are in sequence - All the small letters are in sequence - All the digits are in sequence - letters o A -- 65 a -- 97 0 -- 48 o B -- 66 b -- 98 1 -- 49 o .. .. .. o Z - 90 z - 122 9 -- 57

Other Formatting Flags

• Other flags - cout << left; // left-justify - cout << right; // right-justify (default) - cout << scientific; //scientific notation (default) - cout << setfill('*'); //use * as a fill character instead of space cout << setfill('*') << setw(5) << 3; //outputs ****3

Data Types, Cont.

• Real numbers - Numbers with a fractional part: 3.45, 3, - 3.4, 4.5e3, -45.67e-3 (scientific notation) - float 4 bytes, Å}1.18Å~10−38 to Å}3.4Å~1038 - double 8 bytes, ±2.23Å~10−308 to ±1.80Å~10308 - long double 10/16 bytes, 10-4932 to 104932 - double and long double provide more accurate floating point data

High Level Languages

• Require a compiler and a linker - Compiler o Translates a high-level language into machine language (creates the object code) o Finds parse/syntax errors: errors that violate the rules/grammar of the language - Linker o Links translated code with other built-in code and creates an executable file

First Bug

• September 9, 1947 • First Instance of Actual Computer Bug Being Found • At 3:45 p.m., Grace Murray Hopper records the first computer bug in her logbook as she worked on the Harvard Mark II. The problem was traced to a moth stuck between a relay in the machine, which Hopper duly taped into the Mark II's logbook with the explanation: "First actual case of bug being found."

Formatting, Cont

• Setting the precision - cout << setprecision(p); //p specifies the number of decimal places to show on the screen Example: double value = 123.23456; cout << setprecision(3) << fixed; cout << "Value = " << value; //displays Value = 123.235

Precision

• Setting the precision behaves differently for fixed and scientific (default) notation • For fixed: It specifies the number of digits to display after the decimal point • For scientific: It specifies the number of meaningful digits (before and after the decimal point)

Assignment Statement

• Syntax: <variable> = <exp> ; • Examples: length = 5; width = length; length = width = 6; //both length and width are assigned 6 salary = salary + 100; //salary will be the previous salary plus 100

Formatting, Cont.

• The flags settings are in effect until they are changed • Example: to display dollar amounts using a decimal point along with two decimal places cout << fixed << setprecision(2); cout << "The amount is $" << dollars;

Identifier naming style

• Use meaningful identifier (variable) names • Use lower case letters and one the following two styles: - Style 1 (camel case): salary, facultySalary - Style 2: salary, faculty_salary. • Use constant declaration whenever possible. Use all uppercase for constant names. - const double TAX_RATE = 0.25;

Constants

• Using the const qualifier - const double PI = 3.14; - const double TAX_RATE = 25.0; • Mistyping a number is a lot easier than mistyping a constant name

bool Expressions

• Values of type bool are treated like int expressions • true is stored as non-zero usually 1 • false is stored as 0

Main Program

• Variable Declaration - Identify a type, name, and an optional initial value. - Variable name is an identifier. - Naming an identifier must follow the following rules 1. Must start with a letter or an underscore '_' 2. Can only contain letters, digits, and underscores 3. Must not be a reserved word such as int, double, etc. - Choose an identifier name that is meaningful (describes its content)

Expressions Cont.

• What are the values of the following expressions? 3 + 2 * 6 3 / 4 * 2 3 * (3 + 4) // * is required here 3 + 19 % 5 3 * 6 % 25 6 + 3 % 7

Integer Overflow

• What happens when an integer reaches its maximum value? • Try it: short num = 32767; //max value num = num + 1; cout << num; num = -32768; //min value num = num - 1; cout << num;

Variable Declaration

• int first, second; - Define integer variable used to store values in memory locations. • int first = 3, second = 7; - Defines integer variables and initialize them.

string Type

• string is a class, different from the primitive data types discussed so far - Use double quotes around the text to store into the string variable - Requires the following #include directive #include <string> • To declare a variable of type string: string name = "John"; name = name + " Smith"; //concatenation

string Functions

• string name = "Bob Smith"; • name.length() - Returns the length of the string (9). • name.substr(pos, len) - returns the substring of length len starting at position pos. - If len is omitted, then the rest of the string is returned. - Examples: o cout << name.substr(0, 3); ///outputs Bob o cout << s.substr(4); ///outputs Smith