UNIT 2. Introduction to
Computer Programming
UNIT 2. Introduction to Computer
Programming
Algorithm & Flowcharting
COM E 211: Basic Computer Programming
Algorithm & Flowcharting
 Algorithm
 A list of instruction that carries out a process step by step
 Flowchart
 A diagram representing the logical sequence in which a
combination of steps or operations is to be performed
 Is usually a visual representation of an algorithm
 Types of Flowchart:
 Program Flowchart
• Describes graphically in detail the logical operations & steps within a
program
 System Flowchart
• A graphic representation of procedures involved in converting data or
input to data in output form.
COM E 211: Basic Computer Programming
 Advantages of Flowchart
 Language independent
 Enforces user to give attention to significant matters
 Provides an alternative to the usual narrative description
 Easier to understand
 Limitations
 Do not represent a programming language
 Can’t be viewed as a natural means of communication
 Certain details often require a long sequence of interconnected
symbols
 Does not convey why a given set of operations is made
 Do not highlight the important detail since each step receives as
much attention in a flowchart as any other.
COM E 211: Basic Computer Programming
Flowcharting Symbols
 Parallelogram
--- Input / Output
 Rectangle
--- Processing
 Diamond
--- Decision
 Small Circle
--- On-page Connector
 Pentagon
--- Off-page Connector
 Arrow Heads
--- Flow Direction Indicators
 Horizontal / Vertical Lines --- Flow Lines
 Oval
--- Terminal
COM E 211: Basic Computer Programming
Examples for Sequential
 The radius of a circle is equal to 1 unit. Make an
algorithm and draw a flowchart to compute the
corresponding area of the circle and print out the
value of the radius and the area.
 Given three(3) numbers A,B and C. Make an
algorithm and draw a flowchart to compute and
print out the sum, the average and the product of
these values.
COM E 211: Basic Computer Programming
Examples for Branching
 The ABC manufacturing company plans to give a yearend bonus to each of its employees. Make an algorithm
and draw a flowchart which will compute the bonus of an
employee. Consider the following criteria: If the
employee’s monthly salary is less than 1,000, the bonus
is 50% of the salary. If the salary is grater than 1,000, the
bonus is 1,000. Print out the name and corresponding
bonus of the employee.
 Given two (2) numbers, x and y. Make an algorithm and
draw a flowchart to determine the difference between x
and y. If x-y is negative, compute R=x+y; if x-y is zero,
compute R=2x+2y; and if x-y is positive, compute R=x*y.
Ptint out the values, x, y and R.
COM E 211: Basic Computer Programming
Loops and Counter
 Looping
 Used when it is desired to make the same calculation of more than one set of
data. It consists of repeating a program, or a section of program and substituting
new data for each repetition.
 Counter
 Is a setup in a program loop to keep track of a number of times the program
segment is repeated. The program can then be terminated after the completion
of a predetermined number of passes.
 Steps in Loop Control
 Initialization
 The value of counter is initially set equal to zero or one.
 Test for limit condition
 Before the logic flow gets out of a loop, a loop terminating condition must first be
satisfied.
 Incrementation
 Often each loop is executed, 1 is added to the counter. Thus counter reflects the
number of times the operation has been performed.
COM E 211: Basic Computer Programming
Examples for Looping
 The initial value of the radius of a circle is equal to one
unit and each succeeding radius is one unit greater than
the values before it. Make an algorithm and draw a
flowchart to compute the area of the circle starting with
R=1.0 up to R=5.0, then print out each radius and
corresponding area of the circle.
 Given a set of five (5) numbers that includes both
positive and negative data values. Make an algorithm
and draw a flowchart to read in these values one at a
time and count the number of positive values (including
zero value) and the number of negative values found in
the set. After the required values are determined, print
out these counted values.
COM E 211: Basic Computer Programming