BMS 201

Computer
programming
 Introduction
• Program - A precise sequence of steps that
computer obeys in order to solve a given
problem or perform a given task(s)
• Programming language – A special software
used to develop programs and applications
• Examples of programming languages - Basic,
COBOL, FORTRAN, C++, Java, Html, CSS
• Software – A collection of programs together
with their associated documentation
 DUTIES OF A COMPUTER PROGRAMMER

• Trains software users within an organization

• Advises the management about software-related
matters
• Maintains updated documentations and records
about the corporate software
• Evaluates and modifies the existing software
• Designs and develops computer programs in a
business organization
• Handle users problem relating to a particular
program – user support
 Generations of programming
languages
• First Generation – Machine Languages
• Second Generation – Assembly Languages
• Third Generation – Procedural or Problem
Oriented Languages
• Fourth Generation – Non Procedural
Language
• Fifth Generation – Natural Languages
First Generation – Machine Languages
• Used binary numbers to code programs
• 1100011001110011011100011001
• Programs were difficult to code and debug
• Programmers were required to memorize
memory codes
• 11001 11111 11110 – subtract - sub
• Executed directly without translation
• Programs were machine dependent
 Second Generation – Assembly
Languages
• Replaced binary numbers with mnemonics to
code programs
• Mnemonics are symbolic program codes for
e.g. SUB for subtract and ADD for Address
• Programmers were required to memorize
memory codes
• Assemblers translated the programs into
machine language
• Programs were machine dependent
 Third Generation – Procedural
Languages
• Greatly revolutionized programming
• Introduced English statements in
programming to make coding easy
• Programs were much easier to write and code
since programmers did not have to memorize
memory codes
• Programs were machine independent i.e.
could run on any type of computer
 Third Generation – Procedural
Languages
• Introduced library of in built programs so all
programs did not have to be written from
scratch
• Used compilers and interpreters to translate
the programs into machine code
• Were procedural requiring precise sequence
of steps to perform tasks
• Classified into business, scientific and
multipurpose languages
 Third Generation – Procedural
Languages
• Scientific languages - These are algebraic formula type
designed to meet typical scientific processing
requirement such as mathematical equations, iterative
processing, matrix manipulations etc. They include
FORTRAN – Formula Translator & APL -A programming
language.
• Business Oriented languages - are designed to be
effective tools for developing business information
systems. They include COBOL- Common business
oriented language & PG – report program generator.
• Multipurpose languages - are equally effective for
both scientific and business applications. They include
BASIC – Beginners All-purpose Symbolic Instruction
Code , Pascal – Named after a French mathematician
Blaise Pascal & C
 Fourth Generation – Non procedural
Languages
• Non procedural - Do not require specific
sequence of steps to perform a given task.
• They are optimized for database manipulation
by requiring programmers to only provide
what is to be done and not how to do it.
• These greatly simplify programming.
• They included languages such as structured
query language SQL, query by example QBE
Fifth Generation – Natural languages
• These are advanced programming languages
that are not constrained by syntax, keywords
or specific programming vocabulary.
• Programmers can develop codes as naturally
as instructing a fellow human being to
perform a given tasks.
• Examples include object oriented languages
such as prolog, Java, C++, Perl, Python
 Low level languages
• They are difficult to learn and to program in.
• They are far from human languages therefore
difficult to understand.
• They are fast in execution they need no or
minimum translation.
• They are difficult to modify, maintain and debug.
• They provide facility to write programs at
hardware level.
• They are machine dependent.
• They do not use library of built in codes
 High level languages
• High-level languages are easy to learn and program in.
• They are near to human languages hence easy to
understand.
• Programs in high-level languages are slow in execution
they have to be translated into machine language.
• They are easy to modify, maintain and debug.
• High-level languages do not provide much facility at
hardware level.
• These languages are normally used to write application
programs.
• Machine independent
• Incorporate library of inbuilt functions
 Types of Programming Languages
• C++
• COBOL
• JAVA
• CSS
• HTML
• VISUAL BASIC
• C
• PYTHON
 Choice of programming language
• Type of application - commercial or scientific.
• Facilities required in the application – e.g.
speed of execution
• Availability of the language
• Availability of programmers
• Development costs
• Compatibility of the language
• Maintenance costs
 STEPS IN PROGRAM DEVELOPMENT
• Generate program objectives/Problem Defn
• Design program / Algorithm Development
• Write the program Code/Coding
• Compile the code
• Execute or run the program
• Test and debug the program
• Maintenance and modification
• Documentation of Software
 FLOWCHART DEVELOPMENT
• Flowcharts are Pictorial representation of the
program logic
• They help analyze the problem in more
effective way.
• Program flowcharts serve as a good program
documentation.
• Act as a guide during the systems analysis and
program development phase.
• The flowchart helps in debugging process.
• Provides means of communication with others
about the program
 TYPES OF FLOW CHARTS
• Document flowcharts: showing a document
flow through a system
• Data flowcharts: showing data flows in a
system
• System flowcharts: showing controls at a
physical or resource level
• Program flowchart: showing the controls in a
program within a system
 FLOWCHART SYMBOLS

• Start / Stop Symbol: this is depicted

using an elliptical or a rectangle with
rounded corners symbol. Shows the
beginning and end of the flowchart
• Diagram
 FLOWCHART SYMBOLS
• Process / Computational Symbol:
This is represented using a
rectangular symbol; and the type of
the process or computation is
written inside the symbol
• Diagram
 FLOWCHART SYMBOLS
• Input / Output Symbol: This is
depicted by a parallelogram-like
symbol as shown below. Captures
input and output into the flowchart
• Diagram
 FLOWCHART SYMBOLS
• Decision Symbol: A decision –
making point is represented using a
diamond symbol. Used for making
selection or taking alternatives in
decision making
• Diagram
 FLOWCHART SYMBOLS
• Connector Symbol: This is
represented with a circular symbol,
in which two parts of a program
flowchart join or connect.
• Diagram
 FLOWCHART SYMBOLS
• Flow line: This is depicted by using a
straight line with an arrow at the
end. It shows the direction of flow in
a program.
• Diagram
 FLOWCHART SYMBOLS
• Off – Page Connector: This symbol
enables a programmer to connect to
a flowchart that is continued into a
second or another page, and is
shown using a trapezium
• Diagram
 GUIDELINES FOR DRAWING A
FLOWCHART
• In drawing a proper flowchart, all necessary
requirements should be listed out in logical
order.
• The flowchart should be clear, neat and easy
to follow. There should not be any room for
ambiguity in understanding the flowchart.
• The usual direction of the flow of a procedure
or system is from left to right or top to
bottom.
 GUIDELINES FOR DRAWING A
FLOWCHART
• Only one flow line should come out from a
process symbol
• Only one flow line should enter a decision
symbol, but two or three flow lines, one for
each possible answer, should leave the
decision symbol.
• Only one flow line is used in conjunction with
terminal symbol.
1. Start
2. Product = 1
3. Count = 0
4. Input number Num
5. Sum = Sum + Num
6. Count = Count + 1
7. If Count < 35 then
8. Go to step 4
9. Else
10.Print Sum
11.End if
12.End
 GUIDELINES FOR DRAWING A
FLOWCHART
• Write within standard symbols briefly.
• For complex flowchart use connector symbols
to reduce the number of flow lines.
• Avoid the intersection of flow lines
• Ensure that the flowchart has a logical start
and end.
• It is useful to test the validity of the flowchart
by passing through it with a simple test data.
Dry Running
 FLOWCHARTING EXAMPLES
• Example 1
• Write an algorithm that can be used in
calculating and outputting the sum of the first
35 natural numbers
• Convert the algorithm mentioned in (a) above
into a flowchart
• Draw a flowchart to find the largest of three
numbers A, B and C.
1. Start
2. Sum = 0
3. Count = 0
4. Input number Num
5. Sum = Sum + Num
6. Count = Count + 1
7. If Count < 3 then
8. Go to step 4
9. Else
10.Print sum
11.End if
12.End
 LIMITATIONS OF USING
FLOWCHARTS
• Complex logic: The program logic can be quite
complicated making the flowchart complex
and clumsy.
• Modifications: if alterations are required the
flowchart may require re-drawing completely.
• Reliability: the essentials of what is done can
easily be lost in the technical details of how it
is done.
 Flowchart Exercises
• As a programmer, you are told to write a
program for computing the sum of the first 20
positive integers. The program is supposed to
output the sum after computing
• Write an algorithm for performing the above
task
• Rewrite the above algorithm using the
flowchart method
 ALGORITHM
1. Start
2. Num = 0
3. Sum = 0
4. Sum = sum + num
5. Num = num + 1
6. If num <= 20 then
7. Go to step 4
8. Else
9. Print sum
10. Stop
 Flow Chart Exercises
• A supermarket is planning to give discounts to its
customers based on the total costs of purchases made
by the customer. Discounts are given as follows:
• Total sales exceeding 5000/=, discount is 8%
• Sales greater than 3000/= and less than 5000/=,
discount is 5%
• Sales greater than or equal to 1500/= and less than
3000/=, discount is 2%
• Sales less than 1500/=, no discount
• Required: Develop an algorithm and draw up a
flowchart for a program that can be used to control this
process
 ALGORITHM
1. Begin
2. Get Totsale (Total Sales)
3. If Totsale > 5000 then
4. Discount = 8% * Totsale
5. Elseif Totsale >=3000 and Totsale < 5000 then
6. Discount = 5% * Totsale
7. Elseif Totsale >=1500 and Totsale < 3000 then
8. Discount = 2% *Totsale
9. Else
10.Discount =0
11.Print Totsales
12.Print Discount
13.End