Chapter 1
Introduction to Computers and
C++ Programming
Copyright © 2020 Prof. Amr El-Kadi.
Overview
1.1 Computer Systems
1.2 Programming and Problem Solving
1.3 Introduction to C++
1.4 Testing and Debugging
1.1
Computer Systems
Copyright © 2020 Prof. Amr El-Kadi.
Computer Systems
A computer program is…
A set of instructions for a computer to follow
Computer software is …
The collection of programs used by a computer
Includes:
Editors
Translators
System Managers
Hardware
Three main classes of computers
PCs (Personal Computer)
Relatively small used by one person at a time
Workstation
Larger and more powerful than a PC
Mainframe
Still larger
Requires support staff
Shared by multiple users
Networks
A number of computers connected to
share resources
Share printers and other devices
Share information
Computer Organization
Five main components
Input devices
Allows communication to the computer
Output devices
Allows communication to the user
Processor (CPU)
Main memory
Memory locations containing the running program
Secondary memory
Permanent record of data often on a disk
Computer Organization (cont.)
Computer Memory
Main Memory
Long list of memory locations
Each contains zeros and ones
Can change during program execution
Binary Digit or Bit
A digit that can only be zero or one
Byte
Each memory location has eight bits
Address
Number that identifies a memory location
Larger Data Items
Some data is too large for a single byte
Most integers and real numbers are too large
Address refers to the first byte
Next few consecutive bytes can store the
additional bits for larger data
Computer Memory
Data or Code?
‘A’ may look like 01000001
65 may look like 01000001
An instruction may look like 01000001
How does the computer know the meaning
of 01000001?
Interpretation depends on the current instruction
Programmers rarely need to be concerned with
this problem.
Reason as if memory locations contain letters and
numbers rather than zeroes and ones
Secondary Memory
Main memory stores instructions and
data while a program is running.
Secondary memory
Stores instructions and data between sessions
A file stores data or instructions in
secondary memory
Secondary Memory Media
A computer might have any of these
types of secondary memory
Hard disk
Fast
Fixed in the computer and not normally removed
Floppy disk
Slow
Easily shared with other computers
Compact disk
Slower than hard disks
Easily shared with other computers
Can be read only or re-writable
Memory Access
Random Access
Usually called RAM
Computer can directly access any memory location
Sequential Access
Data is generally found by searching through
other items first
More common in secondary memory
The Processor
Typically called the CPU
Central Processing Unit
Follows program instructions
Typical capabilities of CPU include:
add
subtract
multiply
divide
move data from location to location
Computer Software
The operating system
Allows us to communicate with the computer
Is a program
Allocates the computer’s resources
Responds to user requests to run other
programs
Common operating systems include…
UNIX Linux DOS
Windows Macintosh VMS
Computer Input
Computer input consists of
A program
Some data
High-level Languages
Common programming languages include …
C C++ Java Pascal Visual Basic FORTRAN Perl
PHP Lisp Scheme Ada C# Python
These high – level languages
Resemble human languages
Are designed to be easy to read and write
Use more complicated instructions than
the CPU can follow
Must be translated to zeros and ones for the CPU
to execute a program
Low-level Languages
An assembly language command such as
ADD X Y Z
might mean add the values found at x and y
in memory, and store the result in location z.
Assembly language must be translated to
machine language (zeros and ones)
0110 1001 1010 1011
The CPU can follow machine language
Compilers
Translate high-level language to
machine language
Source code
The original program in a high level language
Object code
The translated version in machine language
Compilers
Linkers
Some programs we use are already compiled
Their object code is available for us to use
For example: Input and output routines
A Linker combines
The object code for the programs we write
and
The object code for the pre-compiled routines
into
The machine language program the CPU can
run
Linkers
History Note
First programmable computer
Designed by Charles Babbage
Began work in 1822
Not completed in Babbage’s life time
First programmer
Ada Augusta, Countess of Lovelace
Colleague of Babbage
Section 1.1 Conclusion
Can you…
List the five main components of a computer?
List the data for a program that adds two numbers?
Describe the work of a compiler?
Define source code? Define object code?
Describe the purpose of the operating system?
1.2
Programming and Problem-
Solving
Copyright © 2020 Prof. Amr El-Kadi.
Algorithms
Algorithm
A sequence of precise instructions that
leads to a solution
Program
An algorithm expressed in a language the
computer can understand
Algorithms
Program Design
Programming is a creative process
No complete set of rules for creating a program
Program Design Process
Problem Solving Phase
Result is an algorithm that solves the problem
Implementation Phase
Result is the algorithm translated into a
programming
language
Problem Solving Phase
Be certain the task is completely specified
What is the input?
What information is in the output?
How is the output organized?
Develop the algorithm before implementation
Experience shows this saves time in getting
your program to run.
Test the algorithm for correctness
Implementation Phase
Translate the algorithm into a programming
language
Easier as you gain experience with the language
Compile the source code
Locates errors in using the programming language
Run the program on sample data
Verify correctness of results
Results may require modification of
the algorithm and program
Implementation Phase
Object Oriented Programming
Abbreviated OOP
Used for many modern programs
Program is viewed as interacting objects
Each object contains algorithms to describe
its behavior
Program design phase involves designing
objects and their algorithms
OOP Characteristics
Encapsulation
Information hiding
Objects contain their own data and algorithms
Inheritance
Writing reusable code
Objects can inherit characteristics from other objects
Polymorphism
A single name can have multiple meanings depending
on its context
Software Life Cycle
Analysis and specification of the task
(problem definition)
Design of the software
(object and algorithm design)
Implementation (coding)
Maintenance and evolution of the system
Obsolescence
Section 1.2 Conclusion
Can you…
Describe the first step to take when creating
a program?
List the two main phases of the program
design process?
Explain the importance of the problem-solving phase?
List the steps in the software life cycle?
1.3
Introduction to C++
Copyright © 2020 Prof. Amr El-Kadi.
Introduction to C++
Where did C++ come from?
Derived from the C language
C was derived from the B language
B was derived from the BCPL language
Why the ‘++’?
++ is an operator in C++ and results in a cute pun
C++ History
C developed by Dennis Ritchie at AT&T
Bell Labs in the 1970s.
Used to maintain UNIX systems
Many commercial applications written in c
C++ developed by Bjarne Stroustrup at AT&T
Bell Labs in the 1980s.
Overcame several shortcomings of C
Incorporated object oriented programming
C remains a subset of C++
A Sample C++ Program
A simple C++ program begins this way
#include <iostream>
using namespace std;
int main()
{
And ends this way
return 0;
}
A Sample C++
Program
Explanation of code (1/5)
Variable declaration line
int number_of_pods, peas_per_pod, total_peas;
Identifies names of three variables to name numbers
int means that the variables represent integers
Explanation of code (2/5)
Program statement
cout << “Press return after entering a number.\n”;
cout (see-out) used for output to the monitor
“<<“ inserts “Press…a number.\n” in the data
bound for the monitor
Think of cout as a name for the monitor
“<<“ points to where the data is to end up
‘\n’ causes a new line to be started on the monitor
Explanation of code (3/5)
Program statement
cin >> number_of_pods;
cin (see-in) used for input from the keyboard
“>>” extracts data from the keyboard
Think of cin as a name for the keyboard
“>>” points from the keyboard to a variable where the data
is stored
Explanation of code (4/5)
Program statement
total_peas = number_of_pods * peas_per_pod;
Performs a computation
‘*’ is used for multiplication
‘=‘ causes total_peas to get a new value based on
the calculation shown on the right of the equal sign
Explanation of code (5/5)
Program statement
cout << number_of_pods;
Sends the value of variable number_of_pods
to the monitor
Program Layout
Program Layout (1/3)
Compiler accepts almost any pattern of line
breaks and indentation
Programmers format programs so they
are easy to read
Place opening brace ‘{‘ and closing brace ‘}’
on a line by themselves
Indent statements
Use only one statement per line
Program Layout (2/3)
Variables are declared before they are used
Typically variables are declared at the beginning of
the program
Statements (not always lines) end with a semi-colon
Include Directives
#include <iostream>
Tells compiler where to find information about items
used in the program
iostream is a library containing definitions of cin and
cout
Program Layout (3/3)
using namespace std;
Tells the compiler to use names in iostream in
a “standard” way
To begin the main function of the program
int main()
{
To end the main function
return 0;
}
Main function ends with a return statement
Running a C++ Program
C++ source code is written with a text
editor
The compiler on your system converts
source code to object code.
The linker combines all the object code
into an executable program.
C++11
C++11 (formerly known as C++0x) is the most recent
version of the standard of the C++ programming
language.
Approved on August 12, 2011 by the International
Organization for Standardization.
C++11 language features are not supported by older
compilers
Check the documentation with your compiler to determine
if special steps are needed to compile C++11 programs
e.g. with g++, use extra flags of –std=c++11
Run a Program
Obtain code in Display 1.10
Compile the code
Fix any errors the compiler indicates and
re-compile the code
Run the program
Now you know how to run a program on
your system
Run a Program
Section 1.3 Conclusion
Can you…
Describe the output of this line?
cout << “C++ is easy to understand.”;
Explain what this line does?
cin >> peas_per_pod;
Explain this? #include <iostream>
1.4
Testing and Debugging
Copyright © 2020 Prof. Amr El-Kadi.
Testing and Debugging
Bug
A mistake in a program
Debugging
Eliminating mistakes in programs
Term used when a moth caused a failed relay
on the Harvard Mark 1 computer. Grace Hopper
and other programmers taped the moth in logbook
stating:
“First actual case of a bug being found.”
Program Errors
Syntax errors
Violation of the grammar rules of the language
Discovered by the compiler
Error messages may not always show correct location of
errors
Run-time errors
Error conditions detected by the computer at run-time
Logic errors
Errors in the program’s algorithm
Most difficult to diagnose
Computer does not recognize an error
Section 1-4 Conclusion
Can you…
Describe the three kinds of program errors?
Tell what kind of errors the compiler catches?
What kind of error is produced if you forget a
punctuation symbol such as a semi-colon?
Tell what type of error is produced when a program
runs but produces incorrect results?
