C++ Chapter 1 Introduction to Computers & Programming

Main Hardware Component Categories

1. Central Processing Unit (CPU) 2. Main Memory 3. Secondary Memory / Storage 4. Input Devices 5. Output Devices 6. Buses

The Programming Process

1. Clearly define what the program is to do 2. Visualize the program running on the computer 3. Use design tools such as a hierarchy chart, flowcharts, or psuedocode to create a model of the program. 4. Check the model for logical errors 5. Type the code, save it, and compile it 6. Correct any errors found during compilation. Repeat steps 5 & 6 as many times as necessary 7. Run the program with test data for input 8. Correct any errors found while running the program. Repeat steps 5 through 8 as many times as necessary. 9. Validate the results of the program.

1. Display a message on the screen asking "How many hours did you work?" 2. Wait for the user to enter the number of hours worked. Once the user enters a number, store it in memory. 3. Display a message on the screen asking "How much do you get paid per hour?" 4. Wait for the user to enter an hourly pay rate. Once the user enters a number, store it in memory. 5. Multiply the number of hours by the amount paid per hour, and store the result in memory. 6. Display a message on the screen that tells the amount of money earned. The message must include the result of the calculation performed in Step 5

1. Display a message on the screen asking "How many hours did you work?" (Input) 2. Wait for the user to enter the number of hours worked. Once the user enters a number, store it in memory. 3. Display a message on the screen asking "How much do you get paid per hour?" (Input) 4. Wait for the user to enter an hourly pay rate. Once the user enters a number, store it in memory. 5. Multiply the number of hours by the amount paid per hour, and store the result in memory. (Process) 6. Display a message on the screen that tells the amount of money earned. The message must include the result of the calculation performed in Step 5 (Output)

Central Processing Unit (CPU)

Comprised of: • Control Unit - Retrieves and decodes program instructions - Coordinates activities of all other parts of the computer • Arithmetic & Logic Unit - Hardware optimized for high-speed numeric calculation - Hardware designed for true/false, yes/no decisions

Input, Processing, and Output

Three steps that a program typically performs: 1) Gather input data: ▪ from keyboard ▪ from files on disk drives 2) Process the input data 3) Display the results as output: ▪ send it to the screen ▪ write to a file

From a High-Level Program to an Executable File

a) Create file containing the program with a text editor. b) Run preprocessor to convert source file directives to source code program statements. c) Run compiler to convert source program into machine instructions. d) Run linker to connect hardware-specific code to machine instructions, producing an executable file. • Steps b-d are often performed by a single command or button click. • Errors detected at any step will prevent execution of following steps.

program

instructions in computer memory to make it do something

programmer

person who writes instructions (programs) to make computer perform a task

computer

programmable machine designed to follow instructions

Programs and Programming Languages

• A program is a set of instructions that the computer follows to perform a task • We start with an algorithm, which is a set of well-defined steps. Types of languages: - Low-level: used for communication with computer hardware directly. Often written in binary machine code (0's/1's) directly. - High-level: closer to human language

Variables

• A variable is a named storage location in the computer's memory for holding a piece of data. • In Program 1-1 we used three variables: - The hours variable was used to hold the hours worked - The rate variable was used to hold the pay rate - The pay variable was used to hold the gross pay

Key Words

• Also known as reserved words • Have a special meaning in C++ • Can not be used for any other purpose • Keywords in the Program 1-1: using, namespace, int, double, and return

Machine Language

• Although the previous algorithm defines the steps for calculating the gross pay, it is not ready to be executed on the computer. • The computer only executes machine language instructions • Machine language instructions are binary numbers, such as 1011010000000101 • Rather than writing programs in machine language, programmers use programming languages.

Integrated Development Environments (IDEs)

• An integrated development environment, or IDE, combine all the tools needed to write, compile, and debug a program into a single software application. • Examples are Microsoft Visual C++, Turbo C++ Explorer, CodeWarrior, etc.

Software-Programs That Run on a Computer

• Categories of software: - System software: programs that manage the computer hardware and the programs that run on them. ▪ Examples: operating systems, utility programs, software development tools - Application software: programs that provide services to the user. ▪ Examples: word processing, games, programs to solve specific problems

Punctuation

• Characters that mark the end of a statement, or that separate items in a list • In Program 1-1: , and ;

What is a Program Made of?

• Common elements in programming languages: - Key Words - Programmer-Defined Identifiers - Operators - Punctuation - Syntax

Input Devices

• Devices that send information to the computer from outside • Many devices can provide input: - Keyboard, mouse, touchscreen, scanner, digital camera, microphone - Disk drives, CD drives, and DVD drives

Main Memory

• It is volatile. Main memory is erased when program terminates or computer is turned off • Also called Random Access Memory (RAM) • Organized as follows: - bit: smallest piece of memory. Has values 0 (off, false) or 1 (on, true) - smallest unit of information - byte: 8 consecutive bits. Bytes have addresses. smallest addressable unit of information • Addresses - Each byte in memory is identified by a unique number known as an address. • A variable name is a symbolic address.

Programmer-Defined Identifiers

• Names made up by the programmer • Not part of the C++ language • Used to represent various things: variables (memory locations), functions, etc. • In Program 1-1: hours, rate, and pay.

Secondary Storage

• Non-volatile: data retained when program is not running or computer is turned off • Comes in a variety of media: - magnetic: traditional hard drives that use a moveable mechanical arm to read/write - solid-state: data stored in chips, no moving parts - optical: CD-ROM, DVD - Flash drives, connected to the USB port

Output Devices

• Output is any data the computer sends to the outside world. • That data is displayed on devices known as output devices. • Common output devices: - Monitors - Printers - Speakers

Procedural and Object-Oriented Programming

• Procedural programming: focus is on the process. Procedures/functions are written to process data. • Object-Oriented programming: focus is on objects, which contain data and the means to manipulate the data. Messages sent to objects to perform operations.

Syntax

• The rules of grammar that must be followed when writing a program • Controls the use of key words, operators, programmer-defined symbols, and punctuation

Variable Definitions

• To create a variable in a program you must write a variable definition (also called a variable declaration) • Here is the statement from Program 1-1 that defines the variables: double hours, rate, pay; • There are many different types of data, which you will learn about in this course. • A variable holds a specific type of data. • The variable definition specifies the type of data a variable can hold, and the variable name. • Once again, line 7 from Program 1-1: double hours, rate, pay; • The word double specifies that the variables can hold double-precision floating point numbers. (You will learn more about that in Chapter 2)

Operators

• Used to perform operations on data • Many types of operators: - Arithmetic - ex: +,-,*,/ - Assignment - ex: = • Some operators in Program1-1: << >> = *