The document provides an introduction to flow charts and their symbols used for representing sequences of operations in computing. It explains different types of logic structures including sequential, conditional, and iterative flows, as well as the conversion of algorithms into machine language. Additionally, it discusses the importance of programming languages, particularly high-level languages like C, in making algorithms understandable and executable by computers.

1. Introduction to computers
and Computing

2. Flow Charts
A schematic representation of sequence of
operations to achieve a task.
 Also called “Flow Diagram” or “Flow
Sheet”
This helps us to show the flow of program
graphically.

3. How to represent using Flow Chart?
There are certain symbols that are connected together
to form a complete Flow Chart for a particular problem
These symbols represent:
1. Start/End
2. Read/Print (Input/Output)
3. Arithmetic operations
4. Conditions
5. Connectors
6. Flow line
of the program

4. How to represent using Flow Chart?
(Contd.)
 This sign represents a limitation.
 It shows where the program starts, and where it ends.
START END
The Oval.

5. How to represent using Flow Chart?
(Contd.)
A PARALLELOGRAM
This sign represents an Input or an Output.
READ PRINT

6. How to represent using Flow Chart?
(Contd.)
A RECTANGLE.
S = a + b
 This is where we want to show an arithmetic
function
(+,-,*,/,^), or to give a number or a string it's value.
NOTE: You must never write for example "a + b = s"

7. How to represent using Flow Chart?
(Contd.)
A Square
condition
yes
No
 This represents a condition.
 Inside we write the condition, and if that condition is true,
then the flow branches to “YES” else to “NO”.
NOTE: This sign must always have two exits: "YES", if the
condition is fulfilled and "NO", if the condition is not
fulfilled.

8. How to represent using Flow Chart?
(Contd.)
 These are the flow lines.
 They connect various blocks in a Flow Chart.

9. How to represent using Flow Chart?
(Contd.)
 These are the connectors.
 They connects portion of algorithm and inside
use of start and end symbols.
Module

10. Flow Chart
Algorithms are more easily understood if they mainly
use self-contained modules and
1-Sequence logic or Sequential flow
2-Selection logic or Conditional flow
3-Iterative logic or Repetitive flow

11. Sequence logic (Sequential flow)
Sequence logic are executed in the obvious
sequence. The sequence may be presented
explicitly, by means of numbered steps, or
implicitly , by the order in which the module are
written.
Module A
Module B
Module C

12. Selection Logic (Conditional Flow)
Selection logic employs a number of conditions which lead
to a selection of one out of several alternative
modules. The structures which implement this logic are
called selection structures.
These selection structures fall into three types.
 Single selection ( If structure )
 Double selection ( If/else structure)
 Multiple selection ( if/else if / else or Switch
structure )

13. Selection Logic (Conditional Flow)
Single selection:
The logic of this structure is, If the
condition holds, then Module A , which
may consist of one or more statements is
executed ; otherwise Module A is skipped
and control transfers to the next step of
the algorithm.

14. Selection Logic (Conditional Flow)
Single Selection:
Condition ?
Module A
Yes
No

15. Selection Logic (Conditional Flow)
Double selection:
Condition ?
Module A Module B
No
Yes

16. PSEUDOCODE – Execution of if-
then-else
Multiple selection :
F
T
Break
T
Break
T
Break
F
.
.
.
F

17. Iterative Logic (Repetitive Flow)
The third kind of logic refers to either of two
types of structures involving loops. Each
type begins with a repeat statement and is
followed by a module ,called the body of
the loop.
1-While structure
2-For Structure

18. Iterative Logic (Repetitive Flow)
While Structure :
Condition ?
Module
(body of loop)
No
Yes

19. Iterative Logic (Repetitive Flow)
For Structure :
KR
Is K > S ?
Module
(body of loop)
KK+T
No
Yes

20. Example – Add two numbers, calculate &
print the sum.
A Flow Chart
Start
End
READ a, b
S := a + b
Print S

21. Impact of the computer language
 An algorithm is expressed in abstract terms.
 To be intelligible to a computer, it needs to be
expressed in a language understood by it.
 The only language really understood by a
computer is its own machine language.
 Programs expressed in the machine language
are said to be executable.
 A program written in any other language needs
to be first translated to the machine language
before it can be executed.

22.  A machine language is far too cryptic to be
suitable for the direct use of
programmers.
 A further abstraction of this language is
the assembly language which provides
mnemonic names for the instructions and
a more intelligible notation for the data.
 An assembly language program is
translated to machine language by a
translator called an assembler

23.  Even assembly languages are difficult to work
with.
 High-level languages such as C provide a much
more convenient notation for implementing
algorithms.
 They liberate programmers from having to think
in very low-level terms, and help them to focus
on the algorithm instead.
 A program written in a high-level language is
translated to assembly language by a translator
called a compiler.
 The assembly code produced by the compiler is
then assembled to produce an executable
program.

24. A Simple C Program
 #include <iostream.h>
 int main (void)
 {
 printf("Hello Worldn“);
 }

25. Annotation for the simple c program
 This line uses the preprocessor
directive #include to include the contents
of the header file iostream.h in the
program. Iostream.h is a standard C++
header file and contains definitions for
input and output.

26. Cont…
 This line defines a function called main.
 A function may have zero or more parameters;
these always appear after the function name,
between a pair of brackets.
 The word void appearing between the brackets
indicates that main has no parameters.
 A function may also have a return type; this
always appears before the function name.
 The return type for main is int (i.e., an integer
number).
 All C++ programs must have exactly one main
function. Program execution always begins from
main.

27. Cont…
 This brace marks the beginning of the body of
main.
 This line is a statement.
 A statement is a computation step which may
produce a value.
 The end of a statement is always marked with a
semicolon (;).
 This statement causes the string "Hello Worldn"
to be sent to the printf output stream.
 A string is any sequence of characters enclosed
in double-quotes.
 The last character in this string (n) is a newline
character which is similar to a carriage return on
a type writer.

28.  This brace marks the end of the body of
main.

29. Variable
 A variable is a symbolic name for a memory
location in which data can be stored and
subsequently recalled.
 Variables are used for holding data values so that
they can be utilized in various computations in a
program.
 All variables have two important attributes:
 A type which is established when the variable is
defined (e.g., integer, real, character). Once defined, the
type of a C variable cannot be changed.
 A value which can be changed by assigning a new
value to the variable. The kind of values a variable can
assume depends on its type. For example, an integer
variable can only take integer values (e.g., 2, 100, -12).