Chapter 8: Introduction to High-level Language Programming Invitation to Computer Science, C++...

Chapter 8: Introduction to High-level Language Programming

Invitation to Computer Science,

C++ Version, Third Edition

Invitation to Computer Science, C++ Version, Third Edition 2

Objectives

In this chapter, you will learn about:

High-level languages

Introduction to C++

Data types

Statement types

Putting the pieces together

Objectives

Managing complexity

Object-oriented programming

Graphical programming

The big picture: software engineering

Where Do We Stand?

Early days of computing

Programmers were satisfied with assembly language

Programs written by technically oriented people

Later decades

Programmers demanded a more comfortable programming environment

Programs could be written by “nontechie” people

High-level Languages

High-level programming languages

Called third-generation languages

Overcame deficiencies of assembly language

Programmer didn’t need to manage details of data storage or movement

Figure 8.1

Transitions of a High-level Language Program

Simple C++ Program/* Get a number input from the user and print it out */

#include <iostream>using std::cout;using std::cin

int main(){ // Prompt user, define a variable for num, input a value.cout << "Please input an integer: ";int num;cin >> num;

// Output resultcout << "The number you entered";cout << " is " << num << "\n";

return 0}

Overall Form of a Typical C++ Program prologue Comment (optional) include directives (optional) using directives (optional) functions (optional) main function{

declarations (optional)main function body

Introduction to C++

Some components of program in Figure 8.2

Comments

Give information to human readers of code

Include directive

The linker includes object code from a library

Using directive

Tells compiler to look in a namespace for definitions not mentioned in the program

Data Types

Identifiers: names in a programming language

Keywords: have special meanings in C++

C++: case-sensitive, free-format language

Data items can be constants or variables

Data Types (continued)

A declaration of a data item tells

Whether the item is a constant or a variable

The identifier used to name the item

The data type of the item

Data Types (continued)

Some of C++ standard data types

int a positive or negative integer

doublea real number( double precision )

float a real number ( single precision )

char a character ( single keyboard character like ‘t’

Data Types(continued)Data Declarations

double radius; Allocates space for a type double data item Associates the name radius with this item Associates a set of valid operations with this item

double circumference = 34.5; Same as above, plus? Gives it an initial value (initializes it)

See sample programs

Data Types(continued)

Data Declarations double radius, circumference, area;

Declares three separate data items of type double

const double PI = 3.1416; Allocates space for type double data item Associates the name PI with this item Associates a set of valid operations with this item Initializes the item with the value 3.1416 Cannot be changed. It is a constant.

Statement Types

Input/output statement

Input statement

Collects a specific value from the user for a variable within the program

Output statement

Writes a message or the value of a program variable to the user’s screen or to a file

Statement Types (continued)

Assignment statement

Assigns a value to a program variable

Control statement

Directs the flow of control

Can cause it to deviate from usual sequential flow

Input/Output Statements

Example Pseudocode

Get value for Radius C++

cin >> Radius;

cin: input stream Code for extraction operator (>>) and the

definition of the cin stream come from the iostream library and std namespace

/*circle01.cpp

Gets the radius of a circle*/

#include <iostream>using std::cin;using std::cout;

int main() { double radius = 0.0;

cout << "Please enter the radius " << '\n';

cin >> radius;

return 0;}

i/o example #1

cout – prompt user for data

<< (insertion operator)

cin – store data in a variable

>> (extraction operator)

Input/Output Statements (continued) Example

Pseudocode Print the value of Circumference

C++ cout << Circumference;

cout: output stream Code for the insertion operator (<<) and the

definition of the cout stream come from the iostream library and std namespace

/*circle02.cpp

Gets the radius of a circle*/

int main() { double radius = 0.0;

cout << "Please enter the radius " << '\n';

cin >> radius;

cout << “The radius you entered is “ << radius;

return 0;}

i/o example #2

cout – output data entered

The Assignment Statement

General form Pseudocode

Set the value of “variable” to “arithmetic expression” C++

variable = expression;

1. Expression on the right is evaluated

2. The result is written into the memory location named on the left

Expressions in C++

Operator Precedence Associativity

( ) 1 na

+, - , ++, -- , ! ( unary ) 2 L->R (+a, -a, ++a, --a, !a)R->L (a++, a--)

*, /, % 3 L->R

+, - 4 L->R

<, >, <=, >= 5 L->R

==, != 6 L->R

&& 7 L->R

|| 8 L->R

= 9 R->L

An expression in C++ is a sequence of operators and operands which adhere to the C++ syntax rules. The operators are grouped according to an order of precedence, and associativity

Expressions in C++

Example 1: a = b + c * d;

Example 2: a = b + c * d – e;

Example 3: a = (b + c) * (d-e);

Example 4: a = b / c;

Example 5: a = b % c;

Example 6: a = b = c – d;

Other: +=, -=, *= , /=, %= ???

Assume b = 5, c = 3, d = 4, e = 2

/*circle03.cpp Gets the radius of a circle, calculates

it’s circumference and prints out the result*/

int main() { const double PI = 3.14159; double radius = 0.0, circumference = 0.0;

cout << "Please enter the radius " << '\n'; cin >> radius; circumference = 2 * PI * radius;

cout << “The circumference is: “ ; cout << circumference << “.\n”;

return 0;}

i/o example #3

cout – output data entered

Control Statements

Types of control mechanisms Sequential

Instructions are executed in order

Conditional Choice of which instructions to execute next

depends on some condition

Looping Group of instructions may be executed many times

Control Statements (continued) Default mode of execution: sequential

Conditional flow of control

Evaluation of a Boolean condition (also called a Boolean expression)

Which programming statement to execute next is decided based on the value of the Boolean condition (true or false)

Control Statements (continued) Conditional flow of control (continued)

if-else statementif (Boolean condition)

S2; if variation of the if-else statement

if (Boolean condition)

Figure 8.12

Conditional Flow of Control

(If-Else)

Figure 8.13

If-Else with Empty Else

Control Statements (continued) Looping (iteration)

The loop body may be executed repeatedly based on the value of the Boolean condition

while statement

while (Boolean condition)

Figure 8.14

While Loop

Data Types Revisited

How to declare a data item which is a group of integers, doubles, chars…

int Hits[12]; // web page hits Allocates space for group of 12 integers Associates the name Hits with this group of integers Associates a set of valid operations with Hits

Each integer in Hits has it’s own ‘name’ The first integer is Hits[0]… the last is Hits[11]

Data Types Revisited

An array Groups together a collection of memory locations,

all storing data of the same type

Figure 8.6

A 12-Element Array Hits

Data Types Revisited(continued)

Declaring a group of arrays ( i.e. a table )

double WaterReadings [2] [3] Allocates space for two arrays of three real numbers

6 total numbers Associates the name WaterReadings with this ‘table’ Associates set of valid operations with this ‘table’

Each element in WaterReadings has it’s own name The number at row 1, column 2 is WaterReadings[1][2] The number at row 0, column 0 is WaterReadings[0][0]

Data Types Revisited(continued) Initializing an array

Int Hits[12] = {3,6,7,22,25,12,34, 9, 3,17,15,2}; Int Hits[ ] = {3,6,7,22,25,12,34, 9, 3,17,15,2};

Same as above

Int Hits[12] = {3,6,7,22}; Initializes first 4 as specified Last 12 get 0

double WaterReadings [2][3] = { {14.3, 15.2, 16.4}, {13.9, 14.2, 12.7} };

int myValue[2][3] = { {0}, {0} }; // ?

Intro to C++

Let’s look at some programs using arrays

Putting the Pieces Together

At this point, we can: Perform input and output

Assign values to variables

Direct the flow of control using conditional statements or looping

For a complete program, we need to: Assemble the statements in the correct order

Fill in the missing pieces

High-level Languages Revisited Expectations of a high-level language program

Programmer can take a macroscopic view of tasks; “primitive operations” can be larger

Programs will be portable

Code will be closer to standard English and use standard mathematical notation

High-level Languages Revisited Consider equation: ax2 + bx + c = 0 The roots are x = ( –b sqrt(b2 – 4ac) ) / 2a Using a high level language we could write:

discrim = b*b – 4*a*c;

root1 = (-b + sqrt(discrim)) / (2*a);

root2 = (-b – sqrt(discrim)) / (2*a);

This closely resembles the way we look at the problemmathematically

Virtual Data Storage

Programs dealing with ‘circles’ might deal with: Circle as geometric shape Circular garden, pool, tile…

Properties of circle Circumference, radius, diameter, area

Relationships among properties Circumference = d = 2 r Area = r2

Virtual Data Storage (continued) Possible Data Items For ‘Circle’ Programs

Radius, Circumference, Diameter, Area and PI

To deal with actual problems what kind of data items should these be?

Numbers with fractional parts double (in C++)

PI never changes const (in C++)

Virtual Data Storage (continued) What if we want to deal with a group of things

that are all the same kind? For Example: a list numbers

Monthly sales figures ( Jan thru Dec ) Midterm exam grades ( 35 of them ) Electoral college votes by state ( 50 of them ) Website hits per month ( Jan thru Dec )

We can declare a group of like data items.

Virtual Data Storage (continued) How to represent a table of the same kind of data items?

Site 1 Site 2 Site 3

FinalReading

14.3 15.2 16.4

InitialReading

13.9 14.2 12.7

Group of arrays?

int Hits1 [12]; int Hits2 [12] = {0}; int Hits3 [12] = {0,1,2,3}; int Hits4 [12] = {0,1,2,3,4,5,6,7,8,9,10,11};

double WaterReadings1 [2][3]; double WaterReadings2 [2][3] = {{0}}; double WaterReadings3 [2][3] = {{14.3,15.2,16.4}}; double WaterReadings4 [2][3] = {{14.3,15.2,16.4},{13.9,14.2,12.7}};

Virtual Data Storage (continued)

Assume these array declarations in C++

Hits1 - elements 0 - 3

-1219546216 134521764 -1073757288 134514065

0 0 0 0 0 0 0 0 0 0 0 0

0 1 2 3 0 0 0 0 0 0 0 0

0 1 2 3 4 5 6 7 8 9 10 11

Virtual Data Storage (continued)

Virtual Data Storage (continued)WaterReadings1 3.76654e-313 -5.74686e-42 -5.74962e-42 -5.64181e-42 -3.24569e-42 4.94066e-324

WaterReadings2 0 0 0 0 0 0

WaterReadings3 14.3 15.2 16.4 0 0 0

WaterReadings4 14.3 15.2 16.4 13.9 14.2 12.7

Meeting Expectations

C++ meets the four expectations for a high-level programming language

Expectations

Programmer need not manage details of the movement of data items within memory, nor pay any attention to where they are stored

Meeting Expectations (continued) Expectations (continued)

Programmer can take a macroscopic view of tasks, thinking at a higher level of problem-solving

Programs written in high-level languages will be portable rather than machine-specific

Programming statements in a high-level language

Will be closer to standard English

Will use standard mathematical notation

Managing Complexity: Divide and Conquer Divide and conquer

To solve a problem, divide it into smaller pieces

In a computer program

Divide the code into modules (subprograms), each doing a part of the overall task

Empower these modules to work together to solve the original problem

Figure 8.19

A Structure Chart

Figure 8.20

A More Detailed Structure Chart

Using Functions

Function

A module of code in C++

Named using ordinary C++ identifiers

Subtask functions: optional

The main function: mandatory

Using Functions (continued)

To invoke a subtask function, the main function gives

Name of the function

Argument list for the function

Argument list: list of identifiers for variables that concern that function

Any function can have its own constant and variable declarations

Writing Functions

A function header consists of:

Return indicator: classifies a function as a void or a nonvoid function

Function identifier

Parameter list

By default, arguments in C++ are passed by value

Figure 8.24

The Outline for a C++ Function

Figure 8.29

Some C++ Terminology

Object-Oriented Programming Object-oriented programming (OOP)

A program is a simulation of some part of the world that is the domain of interest

Each object is an example drawn from a class of similar objects

Key elements of OOP Encapsulation

A class consists of its subtask modules and its properties

Both are “encapsulated” in the class

Object-Oriented Programming (continued) Key elements of OOP (continued)

Inheritance

Once a class A of objects is defined, a class B of objects can be defined as a “subclass” of A

Polymorphism

One name, the name of the service to be performed, has several meanings, depending on the class of the object providing the service

What Have We Gained?

Two major advantages of OOP

Software reuse

A more natural “world view”

Graphical Programming: Graphics Primitives Bitmapped display

The screen is made up of thousands of pixels, laid out in a two-dimensional grid

Frame buffer

Memory that stores the actual screen image

The terminal hardware displays on the screen the frame buffer value of every individual pixel

Figure 8.34

Pixel Numbering System in a Bitmapped Display

Graphics Primitives (continued) Graphics library

Software containing a collection of functions that control the setting and clearing of pixels

Virtually all modern programming languages come with a graphics library

The Big Picture: Software Engineering Software life cycle

Overall sequence of steps needed to complete a large-scale software project

Implementation represents a relatively small part of the cycle

Figure 8.37

Steps in the Software Development Life Cycle

Scaling Up

Programs written by students No longer than a few hundred lines

Real-world programs 2, 3, or 4 orders of magnitude larger

Large-scale software development Extensive planning and design needed

A team of programmers needed

“Software engineering”

The Software Life Cycle

Each step in the software development life cycle

Has a specific purpose and activities

Should result in a written document

The feasibility study

Problem specification

Program design

The Software Life Cycle (continued) Algorithm selection or development, and

analysis

Coding

Debugging

Testing, verification, and benchmarking

Documentation

Maintenance

Modern Environments

Integrated Development Environment (IDE) speeds development by providing

A text editor

A file manager

A compiler

A linker and loader

Tools for debugging

Summary

In a high-level language, the programmer:

Need not manage storage

Can think about the problem at a higher level

Can use more powerful and more natural-language-like program instructions

Can write a much more portable program

Summary

C++ is an object-oriented, high-level programming language

if-else statement creates a conditional flow of control

while loop can be used for iteration

Software life cycle: overall sequence of steps needed to complete a large-scale software project

Chapter 8: Introduction to High-level Language Programming Invitation to Computer Science, C++...

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