PRINCIPLES OF PROGRAMMING

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A Computer

A Computer

A useful tool for solving a great variety of problems.

To make a computer do anything (i.e. solve a problem), you have to write a computer program.

The computer program tells a computer, step by step, exactly what you want it to do.

The computer then executes the program, following each step mechanically, to accomplish the end goal.

Algorithms

The sequence of steps to be performed in order to solve a problem by the computer

Can be expressed as: Natural languages Pseudocode Flowcharts Programming Languages

Natural Language

Direct someone to the Library:1. Assume the person is at the main gate2. Take 35 steps to the fountain that overlooks

the main gate3. Walk past the fountain using the steps

either to the left or right of the fountain.4. Take 50 steps following the pavement after

the fountain.5. The building in front of you is the main

library

Natural Language Example 21. Check patient’s temperature2. Is the temperature less than or greater

than 37 degrees?3. If yes, give a warning4. If no, let the patient know their

temperature is normal

Pseudocode Example

Temp = t1 If (t1 <37)&(t1>37), Warning! Else Temp is Normal OR Temp = t1 If(t1 ≠37), Warning! Else

Temp is Normal

Flow Chart Example

No

Yes

START

Read t1

Is t1=37

?

Temp is Normal

Warning!

STOP

Programming Language

It expresses an algorithm in a way that can be executed by a computer

1. # include<iostream.h>2. using namespace std;3. int main()4. {5. int t1;//t1 is temperature6. cout<<“Enter temperature\n”;7. cin>>t1;8. if(t1!=37)9. cout<<“Warning!\n”;10. else11. cout<<“Your Temperature is normal\n”;12. return 0;13. }

Programming Language

Coded language used by programmers to write instructions that a computer can understand to do what the programmer (or the computer user) wants.Read more: http://www.businessdictionary.com/definition/programming-language.html

Typical C++ development Environment

Understand the C++ Language Errors Syntax Errors Runtime Errors Logical Errors

Printing out a line of text

1. # include <iostream.h>2. using namespace std;3. int main()4. {5. cout<<“Hello World!”;6. return 0;7. }

Escape Sequences

Escape Sequence Description

\n Newline. Position the screen cursor to the beginning of the next line.

\t Horizontal tab. Move the screen cursor to the next tab stop.

\r Carriage return. Position the screen cursor to the beginning of the current line; do not advance to the next line.

\a Alert. Sound the system bell.

\\ Backslash. Used to print a backslash character.

\" Double quote. Used to print a double quote character.

Example Program 2

# include<iostream.h> using namespace std; int main() { int x; int y; x=2; y=4; cout<<x<<“\t”<<y; return 0; }

# include<iostream.h>

using namespace std; int main() { int x, y; x=2; y=4; cout<<x<<“\t”<<y; return 0; }

Example Program 3

1. // Program to add two integers typed by user at keyboard

2. #include <iostream> 3. using namespace std;4. int main()5. {6. int a, b, total;7. cout << "Enter integers to be added:" << endl;8. cin >> a >> b;9. total = a + b; 10. cout << "The sum is " << total << endl;11. return 0;12. }

Definition of terms

Variables Use valid identifiers

Identifier Sequence of letters numbers/digits and

underscores Data type

int, Char, float, double, string Declarations

int x; Initialization

x = 0;

Comments

// this comment spans one line /* this kind of comment is used for more

than one line*/ Documentation For the person reading your code Not interpreted by the compiler

Good Programming practice

Computation statements separated from declaration

1. int a, b, total;2. cout << "Enter integers to be added:"

<< endl;3. cin >> a >> b;4. total = a + b; 5. cout << "The sum is " << total <<

endl; Do not use variables you have not

declared

Decision Making

If statements If – else statements Nested if statements Equality and Relational operators Switch

Repetition

Loops While loop Do- While loop For loop