Computer Science-I (CSIT121)

Dr. Junaid Ahmed Zubairi

SUNY College @ Fredonia

Room 210, Fenton

X-4694, zubairi@cs.fredonia.edu

Introduction In this course, we learn how to use

the computer effectively to solve problems

Let us go over the syllabus and then start the introductory topics.

Syllabus Textbook:

Programming and Problem Solving With C++, 2nd Edition, Nell Dale, Chip Weems and Mark Headington, Jones and Bartlett 2000

Grading System: Assigned Works 40% Exam-I 30% Exam-II 30%

Topics Introduction to Computers Overview of C++ Top Down Design Selection Repetition Function Arguments Formatting and Files Arrays and Structures User defined classes Recursion

Introducing Computers A computer is a device capable of

performing computations What is the difference between a

calculator and a computer? Answer: Taking Logical Decisions Example: if Result=0 then

R1 <= R2*R3-5; elseR1 <= R2

History of Computers 2000BC Abacus used for computations

1890 Hollerith designs electronic census reader and later founds IBM

1939 J. Atanasoff designs first electronic digital computer

1946 Von Neumann proposes stored program computer

1977 Apple Computer launched

1981 IBM PC launched

History of Computers 1970 UNIX first version released

1971 Pascal language developed

1972 C language developed

1973 Part of UNIX implemented in C

1985 C re-implemented as C++

1996 C++ standard released

Types of Computers Microcomputers (PDA, Lap-top,

Desk-top and Workstation computers)

Minicomputers and Mainframes

Supercomputers

Hardware of Computers Computers consist of

CPU Memory (Primary/Secondary) Input devices Output devices

What is a floppy drive? What is a SIMM? What is a modem?

Inside The Computer

INPUT OUTPUT

MEMORY

CPU

CPU Operation

CPU is the brain of the computer It coordinates all operations and

performs specified instructions It has to bring the instructions from

main memory (fetch) It executes the current instruction

as specified (execute) It stores the results in memory if

required

Memory Operation

Memory consists of storage cells that are numbered

Computer can store and retrieve values in memory by addressing the cells and setting bits

A cell may consist of 8 bits in which case it is called a Byte

A bit can only have value 0 or 1.

Types of Memory

Main Memory consists of RAM and ROM.

ROM stores permanent settings for the computer.

RAM stores user programs temporarily when the programs are being executed

A user program cannot run if it is not loaded into RAM

Types of Memory

Secondary Memory consists of Hard disks, floppy disks, CD-ROMS, DVD’s, and tapes etc.

Hard disks contain the operating system of the computer and the user programs and data files.

Floppy disks are removable Tapes are used for backup CD-ROMS distribute software

Input/Output Devices

A keyboard is the most important input device.

Can you identify the most important output device?

Some non-traditional computers require other I/O devices such as control panels, digital displays

What is a NIC?

Programming the Computer Computer speaks ‘1’ and ‘0’ Lowest level programming

language is the machine language it uses Hex or mnemonics to convey 1’s and 0’s to the computer

0x2004=0010 0000 0000 0100 A high-level language would

resemble human-language if price > my_limit then don’t_buy

High Level to Low Level Languages

C++ Program

My_var = this_data+next_data

Compilation and Linking

0001010100111111 //Load R5 from Memory 0001010000111110 //Load R4 from Memory0110011001010100 //Add R4,R5 & store result in R60011011000111101 //Store R6 into Memory

High Level languages

Some high level languages include FORTRAN (Engineering and Science), COBOL (Business), Pascal (Instructional), Lisp (AI), C++, Java (General).

Programs written in these languages are finally translated to ‘1’s and ‘0’s before being executed

A Program’s Stages From Source to Execute

Source File

Compiler Object File

Linker/Loader

ExecutableFile

Sections of Programs

A program running in the computer would have

data input instructions e.g. read (price, my_limit)

data manipulation instructions e.g. is price > my_limit?

data output instructions e.g. write (don’t_buy)

A Problem Solving Strategy Assume that you have a problem

to be solved on computer Think about the problem

specification and identify I/O Plan on program design with data

design and procedural design Implement the program Test and debug the program

NiMo’s varying rates

Example: Niagara Mohawk wants to apply different rates to its customers. If the customer burns more than 1000 units in a month, rate B is applied else rate A is applied. You need to develop a software function that can give the total charges as output given a customer’s consumption.

NiMo’s varying rates

You develop the data model for this problem

What is the input to your function? Answer: consumption, A, B What is the output? Answer: charges What formula to be used? Answer (A or B)*consumption

Top Down Design

If you are given a complex problem, you are better off dividing it into sub-problems

Target is to let each sub-problem deal with one aspect of the software

Thus you can rapidly develop the software to solve complex problems

NiMo’s varying rates

In our example, the program can be divided into three sections:

Answer: Input, processing, output Write a code segment to get the

rates Write a code segment to process

the charges Write a code segment to output the

charges

Algorithm Development

Once given a problem, you need to develop an algorithm to solve it

An algorithm is a series of steps needed in a certain order to solve a problem

Algorithm refinement is done to break it into smaller modules

Desk check is done to make sure it will indeed solve the problem

Software Testing

Once you have coded the program, you should test it to make sure it works

Testing is related to the requirements developed in problem analysis phase

Testing is exhaustive Testing is a specialized field

Documentation

When you develop a program, make sure that you document it properly

Documentation consists mainly of User Guide Administrator Guide Comments in the source code Description of strategy

Maintenance

A program being used requires maintenance over a period of time

What are the reasons for maintenance?

Answer: Bug discovery, finding out some limitations, future expansion of requirements

Example: yy or yyyy for year tracking

Structured Programming Structured programming calls for

Top Down modular design Each module can be refined further

until single-minded modules are achieved

Sharing of data among modules should be reduced to avoid confusion during debugging

Object Oriented Programming An object is a data and procedural

abstraction data represents attributes procedures represent behavior OOP hides attributes and behavior

in classes Classes are used as templates to

create objects

Think about Objects

We find objects everywhere!! A table is an object Table’s attributes include its height,

width, material used etc. Table’s behavior includes its

usage. For example, you can study on a table or eat on a table but you cannot travel on a table!!

Think about Objects

A car is an object The attributes of a car include its

make, model, color, number of seats etc.

The behavior of a car includes stopping on applying brake, accelerating on applying gas, turning, moving from a place to another place

Objects hide information

Objects hide the attributes and behavior from others

Information hiding means the details of implementation are hidden

Objects can communicate through interfaces

Do you need to know how car brakes or accelerator work?

Our Approach

In this course, we primarily focus on structured programming

A good structured programming background would help you a lot in object oriented programming

The behavior of objects will be ultimately built from structured programming constructs

Class Work

Finish the NiMo varying rates program and test it with two sample customers. One customer will have rate A applied and the other one will have rate B applied to the monthly bill.