Computer Programming Computer Programming

 Hardware: Electronic Devices
 Software: Instructions and Computer
Programs

 Input : Keyboard, Mouse
 System unit:
 Random Access Memory (RAM)
 Central Processing Unit (CPU)
 Output: Monitor, Printer
 Secondary Storage: Disk Drive

 Instructions for the hardware.
 Actions to be performed
 A set of instructions is called a program.
 Driving force behind the computer
 Without a program –What is a computer?
▪ Collection of Useless Hardware
 2 purposes:
 Tell the computer what to do
 Tell other people what we want the computer to
do.

 The central processing unit (CPU)
 The “brain” of a computer
 Retrieves instructions from memory and
executes them.

 Stores data and program instructions for CPU
to execute
 A program and its data must be brought to
memory before they can be executed
 Stores intermediate and final results of
processing.
 Volatile: Contents are erased when computer
is turned off or reset.

 A memory unit is an ordered sequence of
bytes, each holds eight bits.
 A byte is the minimum storage unit.
 No two data can share or split the same byte.
 Devices are Hard Drives, CDs/DVDs, Flash
Drives, etc.
 Non-Volatile or Permanent Storage
 Programs and data are permanently stored
on storage devices and are moved to memory
when the computer actually uses them.

 Core operational units of digital devices have
two stable states,
 which are referred to as zero and one by convention
 Combinations of different units with different
states are represented with the binary number
system
 0 and 1.
 A single digit (0 or 1) is called a bit, represents either
of binary states.

 Binary Language
 Data and instructions are encoded as binary
numbers - a series of bits
 one or more bytes made up of zeros and ones

 Encoding and decoding of data into binary is
performed automatically by the system
based on the encoding scheme
 Encoding schemes
 Numeric Data: Encoded as binary numbers
 Non-Numeric Data: Encoded as binary numbers
using representative code
▪ ASCII – 1 byte per character (character means symbol)
▪ Unicode – 2 bytes per character

 Base 10, ten digits (0-9)
 The position (place) values are integral powers of
10:
 100(ones), 101(tens), 102(hundreds), 103(thousands)…
 (372)10 = 3 × 102 + 7 × 101 + 2 × 100
= 3 × 100 + 7 × 10 + 2 × 1
= 300 + 70 + 2
 n decimal digits - 10n unique values

 Base 2, two digits (0-1)
 The position (place) values are integral powers of
2:
 20(1), 21(2), 22(4), 23(8), 24(16), 25(32), 26(64)…
 (101)2 = 1 × 22 + 0 × 21 + 1 × 20
= 1 × 4 + 0 × 2 + 1 × 1
= 4 + 0 + 1
= (5)10
 n binary digits - 2n unique values

 Computers can not use human languages,
 Programming in the binary language of
computers is a very difficult, tedious process
 Therefore, most programs are written using a
programming language
 are converted to the binary language used by the
computer

 Three major categories of programming
languages:
 Machine Language
 Assembly Language
 High level Language

 Natural language of a particular computer
 Primitive instructions built into every
computer
 The instructions are in the form of binary
code
 Any other types of languages must be
translated down to this level

 English-likeAbbreviations used for
operations (Load R1, R8)
 Assembly languages were developed to make
programming easier
 The computer cannot understand assembly
language
 - a program called assembler is used to convert
assembly language programs into machine code

 English-like and easy to learn and program
 Common mathematical notation
 area = radius * radius * 3.1415;
 Java, C, C++, FORTRAN,VISUAL BASIC,
PASCAL

A program written in a high-level language is called a
source program (or source code). Since a computer cannot
understand a source program. Program called a compiler is
used to translate the source program into a machine
language program called an object program.The object
program is often then linked with other supporting library
code before the object can be executed on the machine.
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Compiler
Source File Object File Linker Excutable File

 Programming – the creation of an ordered set of
instructions to solve a problem with a computer.
 Only about 100 instructions that the computer
understands - Different programs will just use
these instructions in different orders and
combinations.
 The most valuable part of learning to program is
learning how to think about arranging the
sequence of instructions to solve the problem or
carry out the task

 Sequential Processing
 A List of Instructions
 Conditional Execution
 if / else
 Repetition
 Looping / Repeating
 Stepwise Refinement /Top-Down Design
 BreakingThings into Smaller Pieces
 Calling Methods / Functions / Procedures / Subroutines
 Calling a segment of code located elsewhere
 Reuse of previously coded code segment

 Procedural
 Defining set of steps to transform inputs into outputs
 Translating steps into code
 Constructed as a set of procedures
 Each procedure is a set of instructions
 Object-Oriented
 Defining/utilizing objects to represent real-world entities that
work together to solve problem
 Basic O-O Programming Components
▪ Class
▪ Object/Instance
▪ Properties
▪ Methods

 The process of defining a problem, searching for
relevant information and resources about the
problem, and of discovering, designing, and
evaluating the solutions for further
opportunities. Includes:
 Finding an Answer to a Question
 Figuring out how to Perform aTask
 Figure out how to MakeThingsWork
 Not enough to know a particular programming
language… Must be able to problem solve…

 Read the Problem: Understand the
description of problem or scenario,
identifying the knowns and unkowns
 Decide how to go about solving the problem:
Determine what steps need to be taken to
reach the solution
 Solve the Problem: Write the solution
 Test the Answer: Make sure the answer is
correct

 In general, when we solve a computing
problem we are taking some inputs,
processing (performing some actions on) the
inputs, and then outputting the solution or
results.
 This is the classic view of computer
programming – computation as calculation
 Polya’s steps (UDIE) can be very effective
when applied to solving computing problems

 What is the Problem to be solved?What is the
unknown?What is the condition?What is the
data?What is needed to solve the problem?
What actions need to take place?
 Identify the inputs and outputs
 Identify the processes needed to produce the
outputs from the given inputs
 Draw a figure. Introduce suitable notation.
 Isolate Principle parts of the problem.

 Find connections between the knowns and
unknowns.
 Simplify: Break the problem into smaller sub-
problems
 Design a solution
 Make a plan or list of actions to implement
the solution
 Algorithm / Flowchart / Psuedocode

 Algorithm
 A FINITE set of clear, executable steps that will eventually
terminate to produce the desired outcome
 Logical design used to solve problems – usually a list of
actions required to perform task
 Pseudocode
 Written like program code but more “English Like” and
doesn’t have to conform to language syntax
 Flowchart
 Diagram that visually represents the steps to be performed
to arrive at solution.

 Implement in a Programming Language
 Carry out the plan checking the preliminary
results at each step.
 Code A LittleTest A lot

 Run the Code
 Check results repeatedly and thoroughly
 Use numerous test cases or data sets
 Use highly varied test case, including expected as
well as and unexpected cases
 Look for new solutions
 Is there a better, easier, or more efficient solution
 Can other problems be solved using these
techniques?

35
 Tools are used to convert algorithms into
computer programs:
 Flowchart - Graphically depicts the logical steps to
carry out a task and shows how the steps relate to
each other.
 Pseudocode - Uses English-like phrases with some
programming terms to outline the program.

36
 How many stamps do you use when mailing a
letter?
 One rule of thumb is to use one stamp for
every five sheets of paper or fraction thereof.

37
1. Request the number of sheets of paper; call it
Sheets. (input)
2. Divide Sheets by 5. (processing)
3. Round the quotient up to the next highest
whole number; call it Stamps. (processing)
4. Reply with the number Stamps. (output)

38
 Graphically depict the logical steps to carry
out a task and show how the steps relate to
each other.

42
 Uses English-like phrases to outline the
task.

43
Determine the proper number of stamps for a
letter
Read Sheets (input)
Set the number of stamps to Sheets / 5 (processing)
Round the number of stamps up to the next
whole number (processing)
Display the number of stamps (output)

44
 Used in problem solving – take a large
problem and break it into smaller problems
solving the small ones first
 Breaks a problem down into modules

45
 Sequence – follow instructions from one line to
the next without skipping over any lines
 Decision - if the answer to a question is “Yes”
then one group of instructions is executed. If
the answer is “No,” then another is executed
 Looping – a series of instructions are executed
over and over

49
 Problem: Given a street number of a one-way
street in NewYork City, decide the direction
of the street, either eastbound or westbound
 Discussion: in NewYork City even numbered
streets are Eastbound, odd numbered streets
areWestbound

51
Program: Determine the direction of a numbered NYC
street
Get street
If street is evenThen
Display Eastbound
Else
Display Westbound
End If

52
 Problem: Calculate and report the grade-point
average for a class
 Discussion: The average grade equals the sum of all
grades divided by the number of students
Output: Average grade
Input: Student grades
Processing: Find the sum of the grades; count the
number of students; calculate average

54
Program: Determine the average grade of a class
Initialize Counter and Sum to 0
DoWhile there are more data
Get the next Grade
Add the Grade to the Sum
Increment the Counter
Loop
ComputerAverage = Sum / Counter
Display Average

 U - Read the Problem Statement
 Identify the inputs, outputs, and processes
 D - Decide how to Solve the Problem
 Create an Algorithm / Flowchart / Psuedocode
 I - Program the Code
 Implement in Programming Language
 E -Test the Solution
 Run the Code using numerous, varied test cases

Using Polya’s first 2 steps, understand and devise a solution to the
following problem:
 Determine the week’s earnings for an employee
from the hourly pay rate and hours worked for the
week. Report the gross earnings (including
overtime earnings) for the week.
 Definitions:
 Overtime hours = hours over 40
 Overtime pay rate = 1.5 * reg pay rate

Using Polya’s first 2 steps, understand and devise a solution to the
following problem:
Determine the week’s earnings for an employee from
the hourly pay rate, total hours for the week and
tax rate. Report the number of reg hours, overtime
hours, gross reg earnings, gross overtime earnings,
tax witheld, and total net earnings for the week.
Definitions:
 Overtime hours = hours over 40
 Overtime pay rate = 1.5 * reg pay rate

 Write an algorithm to serve as how-to
instructions for some relatively simple task or
activity. You choose the task, should be 10-20
steps in length. Assume you are writing
instructions for someone who has never
performed task before.

Computer Programming Computer Programming

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