cisc 1110 introduction to computing using the c++ programming language

CISC 1110

Introduction to Computing

Using the C++ Programming Language

Why Program?

Computer – programmable machine designed to follow instructions

Program – instructions in computer memory to make it do something

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

SO, without programmers, no programs; without programs, the computer cannot do anything

1-2CISC 1110 Introduction to Computing with C++

von Neumann Architecture Although specific components may vary, virtually all modern computers

have the same underlying structure known as the von Neumann architecture named after computer pioneer, John von Neumann, who popularized the

design in the early 1950's The von Neumann architecture identifies 3 essential components

1. Input/Output Devices (I/O) allow the user to interact with the computer2. Memory stores information to be processed as well as programs

(instructions specifying the steps necessary to complete specific tasks)3. Central Processing Unit (CPU) carries out the instructions to process

information


Hardware: The CPUThe Central Processing Unit: (CPU)

Carries out the instructions of the programs.Moves data from one part of machine to another

part of the machine.Manipulates data (e.g., adds, compares, etc.).CPU cycle:

Fetch: get the next program instruction from main memory

Decode: interpret the instruction and generate a signal

Execute: route the signal to the appropriate component to perform an operation


Central Processing Unit (CPU) The CPU is the "brains" of the computer, responsible for controlling its

inner workings made of circuitry – electronic components wired together to control the flow of

electrical signals the circuitry is embedded in a small silicon chip, 1-2 inches square despite its small size, the CPU is the most complex part of a computer

(CPU circuitry can have 10's of millions of individual components) commercial examples: Intel Pentium 4, AMD Athlon, Motorola PowerPC G4


Hardware: Memory

Modern computers are digital devices, meaning they store and process information as binary digits (bits)bits are commonly represented as either 0

or 1bits are the building block of digital memory

by grouping bits together, large ranges of values can be represented


Memory Memory capacity is usually specified in bytes

a byte is a collection of 8 bits – so can represent a range of 28 = 256 values large collections of bytes can be specified using prefixes

Since a byte is sufficient to represent a single character, think of memory in terms of text a kilobyte can store a few paragraphs (roughly 1 thousand characters) a megabyte can store a book (roughly 1 million characters) a gigabyte can store a small library (roughly 1 billion characters) a terabyte can store a book repository (roughly 1 trillion characters)


MemoryInternal Memory

Used to store programs and data that are currently being processed by the CPU

RAM - Random Access MemoryROM - Read Only MemoryBit / Byte / Word

External Memory Used for long term and mass storage of programs

and data magnetic: floppy or hard disk drive, internal or externaloptical: CD or DVD drive flash: USB flash drive


Memory

Main (primary) memory)is fast and expensive memory is volatile – data is lost when the computer is

turned off External (secondary) memory is slower but cheaper

memory is permanent – useful for storing long-term data


Hardware: Input/Output Devices

Input Devices: used to input programs and data into the computer.

keyboard, mouse, microphone, scanner, digital camera, disk drive, CD/DVD drive, USB flash drive

Output Devices: used to receive output information from the computer.

Computer screen, printer, speakers, disk drive, CD/DVD recorder, USB flash drive


Software

Operating system software programs that manage the computer hardware and the

programs that run on the computer controls how the CPU, memory, and I/O devices work

together how many programs can run at once?

Single tasking - one program at a time (MS-DOS) Multitasking – multiple programs at a time (UNIX, Windows

XP/Vista/7) how many people can use computer at the same time?

Single user – MS-DOS, early versions of Windows Multiuser - UNIX

Application software programs that provide services to the user. Ex: word processing, games, programs to solve specific problems


Types of Computers Different types of computers have different characteristics

supercomputers: powerful but expensive; used for complex computations (e.g., weather forecasting, engineering design and modeling)

desktop computers: less powerful but affordable; used for a variety of user applications (e.g., email, Web browsing, document processing)

laptop computers: similar functionality to desktops, but mobile palmtop computers: portable, but limited applications and screen size


Common Desktop Hardware


Machine Languages

The first programming languages were known as machine languages a machine language consists of instructions that correspond directly to

the hardware operations of a particular machine i.e., instructions deal directly with the computer’s physical components including main

memory, registers, memory cells in CPU very low level of abstraction

machine language instructions are written in binary programming in machine language is tedious and error prone code is nearly impossible to understand and debug

excerpt from a machine language program


High-Level Languages In the early 1950’s, assembly languages evolved from machine

languages an assembly language substitutes words for binary codes much easier to remember and use words, but still a low level of abstraction

(instructions correspond to hardware operations)

In the late 1950's, high-level languages were introduced high-level languages allow the programmer to write code closer to the way

humans think (as opposed to mimicking hardware operations) a much more natural way to solve problems plus, programs are machine independent


High-Level Languages

Two high level languages that perform the same task (in JavaScript and C++)


Program TranslationUsing a high-level language, the programmer is able to reason at a high-level of abstraction

but programs must still be translated into machine language that the computer hardware can understand/execute

There are two standard approaches to program translation

Interpreters The interpreter reads one high-level statement at a time,

immediately translating and executing the statement before processing the next one

JavaScript is an interpreted languageCompilers


Compilers The compilation approach relies on a program known as a compiler to

translate the entire high-level language program into its equivalent machine-language instructions

the resulting machine-language program can be executed directly on the computer

most languages used for the development of commercial software employ the compilation technique (C, C++)


High-level Program to Executable


Interpreters and CompilersInterpreter

produces results almost immediately particularly useful for dynamic, interactive features of web

pages program executes more slowly (slight delay between the

execution of statements)Compiler

produces machine-language program that can run directly on the underlying hardware

program runs very fast after compilation must compile the entire program before execution used in large software applications when speed is of the

utmost importance1-20CISC 1110 Introduction to Computing with C++

Simple C++ Programs/* display a message on the monitor */

#include <iostream>

using namespace std;

int main()

{

cout << "Welcome to computer programming!” << endl;

return 0;

}

/* type in a number on the keyboard & echo it to the screen*/

#include <iostream>


int main()

{

int number;

cout << "Type in a number on the keyboard” << endl;

cin >> number;

cout << "The number is “ << number << endl;

return 0;

}

/* a program to do some addition */

#include <iostream>


int main()

{

int number;

cout << "Type in a number on the keyboard” << endl;

cin >> number;

number = number + 5;

cout << "The new number is “ << number << endl;

return 0;

}


The C++ Programming Language

Like any language, C++ has:A Lexicon (a dictionary):

A set of allowable basic elements.A Syntax (a grammar):

Rules for combining the basic elements into programs.

A Semantics (meaning):Rules for understanding what programs and

their parts cause the computer to do.


The Lexical Elements of C++

Keywords and Standard Identifiers:Keywords and Standard (Predeclared)

Identifiers that have special meaning in C++:main char cout for if switch int float cin

while else structCan not be used for another pruposeThe meaning of a keyword is reserved and

can not change.The meaning of a predeclared identifier

can be changed – but it is recommended that you do not.


The Lexical Elements of C++

Identifiers:Words that the writer of the program chooses

to name things (e.g., functions, variables, etc.).

Identifiers must start with a letter or an underbar. The remaining characters are any combination of letters, numerals, and underbars. (Note: upper and lower case are different.)number1 Number1 sum R2D2 Last_Name


The Lexical Elements of C++String Literal:

Anything that is written between double quotes."The final sum is " "hello!"

Numeric Constant:Numerals which express specific numeric

values.5 -227 33.676

Special Characters:Characters or groups of characters that have a

special meaning in C++ (e.g., operators) ; , { } < <= > >= == + - * % & && | ||


The Program Syntax of C++

The Structure of a Simple C++ Program:/* comment on purpose of program */ // comment#directives // compiler directivesusing namespace std; // allows .h header filesint main() // program header { // start of programdata_type list_of_identifiers; // variable declarations<data_type1> <list1>;<data_type2> <list2>;...action part of the program // do program's taskreturn 0;} // end of program


The Program Syntax of C++A variable is a part (location) of memory that is

capable of holding a piece of data that may change its value.

The 'variable declaration' Part of the Program: Indicates how much space in memory that the

action part of the program will need, and the identifiers that will be used to refer to those locations. These identifiers are called the variables of the program.

The Action Part of the Program:The series of C++ statements that accomplish the

program's task.1-27CISC 1110 Introduction to Computing with C++

The Statement Syntax of C++ Rules for combining lexical elements into C++ statements. The Declaration Statement Syntax:

data_type variable_1,...,variable_n; int number; int num1, num2, num3; integer number; // illegal ints num1, num2, num3; // illegal int switch; // illegal

C++ Expressions: an integer constant 3 an identifier x an identifier, an operator, an integer constant sum + 10 an integer constant, an operator, an identifier 10 * y an identifier, an operator, an identifier sum – num

The Assignment Statement Syntax: variable = expression;

z = 33; x = y; sum = number1 + number2 - 5; sqnumber = number * number;


The cout Stetement The cout Statement Syntax:

cout << item1 << item2 << ... << itemN; where << is the insertion operator and each item is either a string literal

or an expression or the stream manipulator

endl endl outs a newline character and flushes the output buffer.

Example:number = 4;sqnumber = number * number;cout<<"The square of “<<number<<“is “<<sqnumber<<endl;

The above code prints:The square of 4 is 16

Another Example: cout << number+1 << endl;


C++ Statement Types C++ statements can be simple or compound. Simple Statement (Examples):

cout << "hello! << endl; x = 25;

Compound Statement:{ statement-list}

Statement-List: A list of C++ statements. Each statement may be simple or compound.

statement; x=3;statement; y=x*2 -3;...statement; cout<<“x= “<<x<<“ y= “<<y<<endl;statement;


Arithmetic Operations Addition:

a + b Subtraction:

a - b Multiplication:

a * b Division:

a / b a % b (yields remainder (or modulus) of integer division)

Examples:int number,sqnumber;int num1,num2;int quotient,remainder;

number = 4;sqnumber = number * number; //sqnumber is assigned 16

num1 = 5;num2 = 37;quotient = num2 / num1; //quotient is assigned 7remainder = num2 % num1; //remainder is assigned 2


Conditions A C++ condition is a Boolean expression of the form:

expression_1 relational_operator expression_2 which takes on the value of either TRUE or FALSE.

Relational Operators:< less than<= less than or equal to== equal to!= not equal to> greater than>= greater than or equal to

Example:Let: n = 15; sum = 11

Then:sum < n TRUEn <= 0 FALSEn > 0 TRUEn >= sum - 1 TRUEn == n + 1 FALSEn + 2 != 17 FALSE


A Complete C++ ProgramProblem: Write a C++ program to compute and print the squares of the integers from 4 to 8.

Program:/* program to print the number from 4 to 8 and their squares */

#include <iostream>


int main()

{

int number,sqnum;

number = 4;

sqnum = number * number;

cout<<"number = “<<number<<“ sqnum = “<<sqnum<<endl;

number = 5;



number = 6;



number = 7;



number = 8;



return 0;

}

Output of the Program:number = 4 sqnum = 16

number = 5 sqnum = 25





Iteration Repeating a Series of Instructions:

number = 4;sqnum = number * number;cout<<"number = “<<number<<“ sqnum = “<<sqnum<<endl;number = 5;sqnum = number * number;cout<<"number = “<<number<<“ sqnum = “<<sqnum<<endl;number = 6;sqnum = number * number;cout<<"number = “<<number<<“ sqnum = “<<sqnum<<endl;

The for statement (or for loop) repeats a group of statements while a control-variable is between its initial and final values.

for (part1; part2; part3) body (statement) of the loop;

wherepart1 - (control variable) initialization statement(s),part2 - a relational test (a boolean expression),part3 - (control variable) update statement(s).body of loop can be either a simple statement or a compound statement enclosed with braces.


Iteration - Examplesfor (j = 1; j <= 10; j = j+1)

cout << j <<endl;

for (number = 8; number >= 4; number = number-1)

{



}

for (number = 4; number <= 6; number = number+1)

{



}


Revised Program with Iteration

Revised Program:

Write a C++ program to compute and print the squares of the integers from 4 to 8.

/* program to print the number from 4 to 8 and their squares */

#include <iostream>


int main()

{

int number,sqnum;

for (number = 4; number <= 8; number=number+1)

{


cout << "number = “ << number<< “ sqnum = “ << sqnum<< endl;

}

return 0;

}

Trace of the Program







Shorthand for Increments and Decrements

Because increments and decrements are so common, C++ has a shorthand notation for these operations:j = j + 1; can be replaced by j++; i = i - 1; can be replaced by i--;

Example: Use in for loopsfor (number = 4; number <= 8; number++){ sqnum = number * number; cout<<"number = “<<number<<“ sqnum = “<<sqnum<<endl;}

Example:for (number = 8; number >= 4; number--){ sqnum = number * number; cout<<"number = “<<number<<“ sqnum = “<<sqnum<<endl;}

Examplefor (i = 1, j = 7; i < j; i=i+3, j++)cout << i <<“,”<< j << endl;

Output:1, 74, 87, 9

Note: ++j will also increment (can be different than j++)Note: --i will also decrement (can be different than i--)


cisc 1110 introduction to computing using the c++ programming language

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