1. Flowcharts

2. Problem Solving using computers
Problem Solving using computers. Flowcharts: A language for expressing ‘Algorithms’

3. Flowcharts A pictorial representation of algorithms;
Flowcharts are not a programming language, rather it is an algorithm specification language;
In an algorithm we specify the computation operations (arithmetic, logical, data input, data output) to be done, and their sequence;
Each type of computation operation is denoted by a special symbol in the flowchart language;
Symbols are connected by arrows to represent the order of the operations (sequence);
Flowchart are useful during algorithm design;
A flowchart can be relatively easily translated to a C++ program.

4. Flowcharts Symbols Calculation (square or rectangle)
You use it to specify a calculation, e.g. arithmetic expression.
Examples:
x = z+y;
a = pi * r*r;
z = z + 1 (add one to the current value of z and make that the new value of z);
c = SQRT(x*x+y*y);
x, z, y, a, c, pi, r are called variables.
z = z +1
c = SQRT(x*x +y*y)

5. Flowcharts Symbols Data Input/Output (parallelogram)
Use it to specify an input or an output operation;
By an input operation we mean a read operation of data from a peripheral device to Main Memory (e.g. user typing on a keyboard );
By an output operation we mean a write operation of data to a peripheral device from Main Memory (e.g. data displayed on the monitor, or sent to the printer);
Examples:
Read a value for the radius r from the keyboard; print value of the area a on the screen.
input a
print a

6. Flowcharts Symbols Decision or condition Testing (Diamond)
Use it to specify a condition to be tested. Based on the condition being true or false the next operation will be determined.
Examples
If (Adjusted Gross Income) > then
taxRate = 0.31
else
taxRate = 0.28 or
if(r < 0 ) then
print “invalid value for the radius”
continue. no
AGI>40000 ?
TR = 0.28
yes
TR = 0.31
You do it as an exercise

7. Flowcharts Symbols Decision or condition Testing cnt’d
A decision is composed of :
A condition;
An operation to be done if condition is true;
An operation to be done if condition is false;
We use decisions to enable repeating a set of operations multiple times; we call this construct a loop.
An example of a loop is
let sum = 0;
do {
input a;
sum = sum+a;
} until (a <0);
sum = 0
input a
sum = sum +a no
a < 0 ?
yes

8. Flowcharts Symbols Start/End
Every algorithm starts somewhere, and terminates somewhere;
Every flowchart must have one start symbol and one or more end symbols;
A start symbol denotes the start of the algorithm;
When an end symbol is encountered this indicates the algorithm has terminated.
start
sum = 0
input a
sum = sum +a
a < 0 ? no
yes
print sum
stop

9. Flowcharts Exercise
Let’s Develop the flow chart for the algorithm that computes the circumference of a circle whose radius r is given as input.
Don’t forget to check if the radius is positive number!
Fig.2