31 address binding, dynamic loading

1. 1
Address binding, Dynamic loading
Storage Management

2. 9CM402.31 2
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3. 3
Recap
In the last class, you have learnt
•Recovery from Deadlock

4. 4
Objectives
On completion of this period, you will be able to
Know about
•Storage management
•Address binding
•Dynamic loading

5. 5
Primary Memory
•Primary memory is of two types RAM and ROM
•RAM – Random Access Memory
– Volatile Memory
– Can be directly accessibly by the CPU
– Speed of RAM is compatible to Processor speed
– Capacity is in GB’s
•ROM – Read Only Memory
–Non Volatile

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Storage Management
•Memory is a large array of words or bytes with its
own addresses
•In Single user operating system entire memory
belongs to a single process
Ex. DOS
•In multi user operating system many processes
share the memory
Ex. UNIX, Windows NT, Windows 2003 server
etc.

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Storage Management
What is meant by storage management?
•Allocate memory to multiple processes and
prevents them from overlapping
•Memory is utilized in an efficient manner

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Instruction Execution Cycle
•Instruction is fetched from memory
•Decoded and may cause operands to be fetched
from memory
•After executing the instruction on the operands
the results are stored back in memory
Start Fetch Execute
Halt
Fig - 1

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Multistep Processing of User Program
Fig - 2

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Address Binding
•Program must be brought into memory and placed
with in a process for it to be run
•Collection of processes on the disk that are waiting
to be brought into memory for execution - Input
queue
•A user program will go through several steps before
being executed as shown in Fig - 2

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Address Binding
•Address is represented in different ways during this
steps
•Address in source program is symbolic (Ex. COUNT)
•Compiler bind these symbolic addresses to
relocatable addresses such as
–14 bytes from the beginning of this module

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Address Binding
•Relocatable means that the program image can
reside anywhere in physical memory
•A linkage editor or a loader bind relocatable
addresses to absolute addresses ( such as
74014 )
•Each binding is a mapping from one address
space to another

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Address Binding
•Binding of instruction and data to memory
address can be done at
–Compile time
–Load time
–Execution time

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Dynamic Loading
•Routine is not loaded until it is called
•All routines are kept on disk in a relocatable
load format
•Main program is loaded and executed
•A routine needs to call another routine

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Dynamic Loading
•The relocatable linking loader is called to load
the desired routine
•Control is passed to newly loaded routine
•Routine is called into memory only when it is
needed

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routine( )
{
------- ;
------- ;
------- ;
}
Memory
•main( )
{
---- ;
---- ;
routine( );
---- ;
}
// routine is called dynamically
Dynamic Loading - Example
Secondary storage

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Advantages
•Better memory utilization
•Unused routine is never loaded
•Useful when large amounts of code are needed
to handle infrequently occurring cases
–Ex. Error routines
–Although the total program size may be large, the
portion i.e., used is much smaller
Dynamic Loading

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•No special support from the operating
system is required
• Implemented through program design
•Operating system provides library
routines to implement dynamic loading
Dynamic Loading
Advantages

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Summary
In this class, you have learnt
• Storage Management
• Address binding
•Dynamic loading
•Advantages of dynamic loading

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Frequently Asked Questions
•What is address binding?
•What is meant by Dynamic loading?
•Explain the concepts of Dynamic loading
•What are the advantages of Dynamic loading?

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Quiz
1. Memory is a large array of
a) Words
b) Registers
c) Bits
d) None

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Quiz
2. Address in source program is address
a) Relocatable
b) Symbolic
c) Absolute
d)None

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Quiz
3. Compiler binds symbolic address to _________
address
a) Absolute
b) Symbolic
c) Relocatable
d) None

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Quiz
4. Loader binds relocatable address to ________
address
a) Absolute
b) Symbolic
c) Relocatable
d) None

29. 29
Quiz
5. All routines are kept on disk in a ______ load
format
a) Relocatable
b) Symbolic
c) Absolute
d) None

30. 30
Quiz
6. Special support from the operating system is
required
a) Yes
b) NO

31. Other subject materials
•Web designing
•Micro processors
•C++ tutorials
•java
home

32. 32
Quiz
7. Routine is not called until it is required in
dynamic loading
a) True
b) False