Introducing block scheme programming

March 17

2

Algorithm / Flow chart An algorithm or a flowchart is a step-by-step procedure for

solving a particular problem, independently of the programming language.

A general plan for solving problems consist of Write the specification of the problem to be solved i.e. inputs,

outputs Draw flowchart or write algorithm Convert flowchart (algorithm) into program code Compile the program into object code Execute the program

3

Flow chart basic symbols

Computations

Input / Output

Decision

Start / stop

Connector

Flow of control

4

Adding the numbers

start

read A, B, C

S = A + B + C

output S

stop

5

Larger of two numbers

start

read X, Y

output X

stop

X > Y ?

output Y

stop

yes no

6

Larger of three numbers

start

read X, Y, Z

stop

X > Y ?

stop

yes no

max > Z ?

Output max Output z

yes no

Max = X Max = Y

7

start

read N

stop

Count > N ?

output sum

no yes

sum = sum + count * count

sum = 0count = 1

count = count + 1

Sum = 12 + 22 + 32 + … + N2

8

start

read N

stop

Count > N ?

output sum

no yes

sum = sum + count * (count + 1)

sum = 0count = 1

count = count + 1

sum = 1 * 2 + 2 * 3 + 3 * 4 + … + N* (N +1)

9

start

read N

stop

count > N ?

output sum

no yes

prod = prod * count

prod = 1count = 1

count = count + 1

Computing factorial

10

start

Read X, N

stop

count > N ?

output sum

noyes

sum = prod * countterm = term * X / count

term = 1prod = 1count = 1

count = count + 1

Computing ex series up to N terms

Use Taylor expansion to represent ex up to N terms.

11

start

Read X, N

stop

term < .0001 ?

output sum

noyes

sum = prod * countterm = term * X / count

term = 1prod = 1count = 1

count = count + 1

Computing ex series up to 4 decimal places

Use Taylor expansion to represent ex up to 4 decimal places.

12

Do you it yourself Draw a block scheme for the algorithm that finds roots of

quadratic equations ax2 + bx + c = 0

13

Homework Draw a flowchart for the following algorithms

1. Find whether a number is prime or not.2. Find sin(x), using the following series

Hint: see problem on slides 10 and 11

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