lecture 1
TRANSCRIPT
PROGRAMMING
FUNDAMENTAL
Engr. Haseeb Ahmad Khan
Course Literature
Text book
Object-Oriented Programming in C++, 3rd Edition
by Robert
Reference
Problem Solving, Abstraction, and Design Using
C++ by Frank L. Friedman, Elliot b. Koffman
Computer Programming in C/C++ by
Muhammad Tariq Siddiqi
Let us C++ by Yashavant Kanetkar
Instructions
A large number of simple operations can do
complex things
Computers require very detailed instructions
High and Low Level Programming
Languages
Low-level language (assembly, machine code)
Makes all operations explicit
Can be executed by the CPU
E.g. “Lift this foot, put it down there, lift that foot,
etc…”
High-level language (C++, Java, C#, etc)
Abstract away details
Simplify common operations
E.g. “Walk from here to there.”
1-6
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
statements into machine instructions
d) Run linker to connect hardware-specific
library code to machine instructions,
producing an executable file
1-7
From a High-level Program to an
Executable File
Steps b)–d) are often performed by a single command or button click
Each step detects certain types of errors
Errors detected at any step will prevent
execution of the following steps
1-8
From a High-level Program to an
Executable File
Object Code
Linker
Executable Code
Source Code
Preprocessor
Modified Source Code
Compiler
1-9
Input, Processing, and Output
Three steps that many programs perform
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 or a printer
- write it to a file
Problem Solving
Programming is a process of problem solving
Good problem solving techniques need to be
followed to become a good programmer
One common problem-solving technique
includes:
Analyzing the problem
Outlining problem requirements
Designing steps to solve the problem
Algorithm
Algorithm
A step by step problem solving process in
which a solution is arrived at in a finite amount
of time
Let’s design an algorithm to find the perimeter
and area of a rectangle
What information do we need to calculate the
perimeter?
Length
Width
How do you calculate perimeter?
Perimeter = 2 x (length + width)
Algorithm
Algorithm to calculate the perimeter of
rectangle is:
Get the length of the rectangle
Get the width of the rectangle
Find the perimeter using the equation
Perimeter = 2 x (length + width)
Algorithms
Algorithm (or in short Algo) to calculate pay of a sales person at a store
Every sales person has a base salary. Every salesperson receive a bonus at the end of the month on the criteria:
If the salesperson has worked in store for less than 5 years, $10 is paid for every year salesperson has worked there
If the salesperson has worked in store for more than 5 years, $20 is paid for every year salesperson has worked here
Algorithm Continued
Salesperson can get additional bonus if:
The sales made are between $5000-$10000,
salesperson receives 3% commission on sale
The sales made are greater than $10000,
salesperson receives 6% commission on sale
Lets suppose:
baseSalary denotes the base salary
noOfServiceYears denotes the number of
years salespersons has worked in the store
totalSale denotes the total sales made by the
salesperson
additionalBonus denotes the additional bonus
Algorithm Continued
1. Get the baseSalary
2. Get noOfServiceYears
3. Calculate bonus using:
if (noOfServiceYears is less than or equal to 5
years)
bonus = 10 x noOfServiceYears
Otherwise
bonus = 20 x noOfServiceYears
4. Get totalSales
Algorithm Continued
5. Calculate addtionalBonus using:
If (total Sale is less than 5000)
additionalBonus = 0
Otherwise if (total sale is greater than or equal to
5000 but less than 10000)
additionalBonus = totalSale x 0.03
Otherwise
addtionalBonus = totalSale x 0.06
6. Calculate payCheck using:
payCheck = baseSalary + bonus +
additionalBonus
The Programming Process
1. Define what the program is to do
▫ Often in terms of inputs and outputs
2. Program design
▫ Break large problems into smaller sub-problems
▫ Design steps to solve those sub-problems
3. Write the program code and compile
▫ The compiler will detect syntax errors in the code
4. Run the program with test data for input
▫ Test data should validate whether the program does what it was designed to do
5. Repeat steps 2-4 until the program is successful
Getting Started
• C++ vs. English
• Syntax: rules about how tokens form statements
• Semantics: what the statements “mean” to the computer (what they instruct it to do)
C++ English
Token Word, punctuation
Statement Sentence
Block Paragraph
Getting Started
• Function: a named block
• By convention, every program must have a function named main
• The simplest C++ program: main()
{
}
• When the program runs, it executes the statements in the main function block
First C++ Program
/* My first simple C++ program */
main ()
{
cout<<“Welcome to C++!”<<endl;
}
Comments
Braces indicate start
and end of main
All C++ programs have a main function;
they also start at main
Function to print to screen
What to print
End of line
End of
statement
Building Statements
• Statements are made by combining tokens
according to the syntax rules
▫ C++ statements end with a ;
• There are several types of tokens
▫ Literals – piece of data
▫ Special symbols
▫ Keywords – reserved words
▫ Identifiers – variable identifiers
Literals
A piece of data
Integer 12
Floating-point Number 3.14
Character (surrounded by single quotes)
'A'
String (surrounded by double quotes) "Hello"
Print Statements
• Prints information on the computer screen
cout << "Hello there!";
cout << "Hello " << "there!";
cout << "Hello ";
cout << "there!";
• To get multiple lines of output on screen use endl
cout << "Hello, there!" << endl;
2-23
Print Statements
• Can print any literal
cout << 17 << “ desks”;
cout << “The letter” << „A‟;
cout << 178.33;
2-24
Comments
• Comments are for the reader, not the compiler
• Two types:
▫ Single line // This is a C++ program. It prints the sentence:
// Welcome to C++ Programming.
▫ Multiple line /*
You can include comments that can
occupy several lines.
*/
A C++ Program
#include <iostream.h>
#include <conio.h>
main()
{
cout << "My first C++ program." << endl;
cout << "The sum of 2 and 3 = " << 5 << endl;
cout << "7 + 8 = " << 7 + 8 << endl;
getch();
}
What do you think is
the output?
Sample C++ program
// This is a C++ Program
#include <iostream.h>
#include <conio.h>
main()
{
/* The output of this program is
just a stupid string
*/
cout << “Welcome to C++." << endl;
getch();
}
Every C++ program has a function called
main
Can you find 2 examples of
comments in the program?
Special Symbols
Special symbols
+
-
*
/
.
;
?
,
<=
!=
==
>=
Reserved Words (Keywords)
Reserved words, keywords, or word symbols
Include:
int
float
double
char
const
void
return
Identifiers
Consist of letters, digits, and the underscore
character (_)
Must begin with a letter or underscore
C++ is case sensitive
NUMBER is not the same as number
Two predefined identifiers are cout and cin
Unlike reserved words, predefined identifiers
may be redefined, but it is not a good idea
I hear and I forget,
I see and I remember,
I do and I understand
-Chinese Proverb