The document provides an introduction to the Bakery algorithm for solving critical sections in operating systems. It discusses: 1. The Bakery algorithm assigns each process a ticket number before entering the critical section, and the lowest number proceeds first. If numbers are equal, the lower process ID goes first. 2. It requires data structures to store choosing flags and ticket numbers for each process. Processes set their choosing flag, get the next highest ticket number, then enter the critical section. 3. An example shows two processes with different ticket numbers, and another with the same number where the lower ID process enters first.

1. Introduction to
Bakery Algorithm
In the name of God
University of UAJ&K
neelum campus
By:
Mehdi Hussain # 36
Khizar Hayyat # 25
Anees Mehdi # 35
Supervisor :
Prof. Sir.Saqib.Khushhal.
Spring 2017
Class presentation for the course: “ Operating System”
All the materials are copy rights of their respective authors as listed in references.

2. Contants:
 Critical Section
Hardware Requirements for Bakery Algorithm
Software Requirements for Bakery Algorithm
 Introduction to Bakery Algorithm
 Bakery Algorithm Notations
 Bakery Algorithm Data Structure
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3. CRITICAL SECTION :
 Critical section is a code segment that accesses
shared variables and has to be executed an
atomic action.
 Only one process must be executing its critical
section at a given time.
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4. CRITICAL SECTION Example :
Do
{
Entry section
Critical section
Exit section
Remainder-section
}
While (true)
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5. CRITICAL SECTION Solutions Criteria:
1.mutual exclusion:
Only one process should
execute in its critical section.
2.progress:
If no process is executing in its
critical section and some process wish to
enter the critical section. Then only those
processes that are not executing in its
remainder section can participate.
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6. CRITICAL SECTION Solutions Criteria:
3.Bounded waiting:
There is a limit on the
number of times that other process are
allowed to enter their critical section.
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7. Hardware Requirements for Bakery Algorithm
•Computers (Laptop ) recent version.
•Ram 4 GB require
•Hard Drive: 30 GB require
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8. Software Requirements for Bakery Algorithm
•Operating System : Unix/linux
•Front End: Vmware Workstaion
•Back End :Fedora
•Language : C/C++
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9. Introduction to Bakery Algorithm:
What is Bakery algorithm?
 Devised by “Leslie Lamport”
Before entering its critical section, process
receives a ticket number. Holder of the
smallest ticket number enters the critical
section.
If processes Pi and Pj receive the same
number, if i < j, then Pi is served first; else Pj
is served first.
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10. 10
Bakery Algorithm
 The ticket numbering scheme always generates numbers in the
increasing order of enumeration; i.e., 1, 2, 3, 4, 5 ..
Pi
Pj

11. 11
Bakery Algorithm
Notations (ticket #, process id #)
(a,b) < (c,d) if a < c or
if a == c and b < d
max (a0,…, an-1) is a number, k, such
that k ≥ ai for i = 0, …, n–1

12. 12
Bakery Algorithm
(Ticket # 25, p1) (Ticket # 24, p2)
in the above diagram we can see that there are two processes p1 and
p2.the process p2 will go to the critical section because it has lowest ticket
number.

13. 13
Bakery Algorithm
(Ticket # 24, p1) (Ticket # 24, p2)
In the above diagram we can see that there are two processes p1 and
p2.the process p1 & p2 have same ticket number .Then process ID will be
checked. P1 process has lowest ID and will go to critical section first

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Data Structures
boolean choosing[n];
int number[n];
These data structures are initialized
to false and 0, respectively
Bakery Algorithm

15. Bakery Algorithm
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do {
choosing[i] = true;
number[i] = max(number[0],
number[1], …,
number [n – 1]) + 1;
choosing[i] = false;
Structure of Pi

16. Bakery Algorithm
16
Critical Section
for (j = 0; j < n; j++) {
while (choosing[j]) ;
while ( (number[j] != 0) &&
((number[j], j) < (number[i], i)) ) ;
}

17. Bakery Algorithm
17
www.cisco.com
remainder section
} while (1);
number[i] = 0;

18. Bakery Algorithm
18
Process Number
P0 3
P1 0
P2 7
P3 4
P4 8

19. Bakery Algorithm
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P0 P2 P3 P4
(3,0) < (3,0) (3,0) < (7,2) (3,0) < (4,3) (3,0) < (8,4)
Number[1] = 0 Number[1] = 0 Number[1] = 0 Number[1] = 0
(7,2) < (3,0) (7,2) < (7,2) (7,2) < (4,3) (7,2) < (8,4)
(4,3) < (3,0) (4,3) < (7,2) (4,3) < (4,3) (4,3) < (8,4)
(8,4) < (3,0) (8,4) < (7,2) (8,4) < (4,3) (8,4) < (8,4)

20. Bakery Algorithm
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