1. Introduction to Computers

2. M. Tawfiqul Islam, Lecturer, CSE, DU
Books
Introduction to Computer
Peter Norton
2. Computer Fundamentals
Dr. M Lutfar Rahman
3. Computer Fundamentals
Pradeep K. Sinha
M. Tawfiqul Islam, Lecturer, CSE, DU

3. Memory Unit

4. M. Tawfiqul Islam, Lecturer, CSE, DU
Memory
Memory:
One or more set of chips that stores data or programmed instructions either temporarily or permanently.
Classification of memory:
Primary memory
Secondary memory
M. Tawfiqul Islam, Lecturer, CSE, DU

5. Location of different memories
ALU
MAIN MEMORY OR
RESISTERS
CONTROL
UNIT
INPUT
OUTPUT
SECONDARY MEMORY
M. Tawfiqul Islam, Lecturer, CSE, DU

6. Calculations of storage capacity
01 BYTE (B)
08 bit
01KB
1024 B
01 MB B
01 GB B
01 TB B

7. M. Tawfiqul Islam, Lecturer, CSE, DU
Memory Terminologies
Memory Address:
Memory locations are identified by numbers
100 B X Y A
0000
0001
0002
FFFD
FFFE
FFFF
M. Tawfiqul Islam, Lecturer, CSE, DU

8. M. Tawfiqul Islam, Lecturer, CSE, DU
Memory Terminologies
Memory Word:
When memory is read or written, a block of bit is read or written instead of a single bit.
The block is considered to be a unit of operation/processing
A set of bit with which read/write operation is done in a certain storage device is called memory word
Example: 08 bits or 01 Byte memory word clearly (08 bits) represents 64 and its character here, this digital 08 bits in combine known as a memory word
100 B X Y A
0000
0001
0002
FFFD
FFFE
FFFF
M. Tawfiqul Islam, Lecturer, CSE, DU

9. M. Tawfiqul Islam, Lecturer, CSE, DU
Memory Terminologies
Destructive:
composed of capacitors, data disappears when read operation is done, needs re-write operation to retain data
Non-destructive:
reverse nature
Example: semiconductor, switch, flash memory, pen drive
M. Tawfiqul Islam, Lecturer, CSE, DU

10. M. Tawfiqul Islam, Lecturer, CSE, DU
Memory Terminologies
Volatile:
Type of memory where data remains only when the power supply is on.
Ex-RAM
Non-volatile:
here content remains even the power is turned off
Example: hard disk, floppy disk, flash drive etc
M. Tawfiqul Islam, Lecturer, CSE, DU

11. Memory Terminologies: Memory operation
Memory store/write:
The process of storing or writing data at the specific location of the memory
Data is stored as bits
Ex- CD writing operation
M. Tawfiqul Islam, Lecturer, CSE, DU

12. Memory Terminologies: Memory operation
Memory read:
Also called ‘fetch operation’
To read stored data or to process that stored data
A binary word is selected from a specific address of memory and this is transferred to another device
Example: To hear a song from CD or any drive
M. Tawfiqul Islam, Lecturer, CSE, DU

13. Memory Terminologies: Memory access
Random access:
Any location of storage can be accessed at any moment
Does not matter whether the desired access location is too close or a far away
Consumes almost same amount of time
Found in primary and secondary memory
M. Tawfiqul Islam, Lecturer, CSE, DU

14. Memory Terminologies: Memory access
Sequential:
accessing a bit of information in a serial order, one after another
Access time depends on the last order/information execution time
Example: Off line storage such as playing a song from magnetic tape
M. Tawfiqul Islam, Lecturer, CSE, DU

15. M. Tawfiqul Islam, Lecturer, CSE, DU
Primary memory
Includes RAM & ROM
CPU access directly on this memory
Normally volatile in nature
M. Tawfiqul Islam, Lecturer, CSE, DU

16. M. Tawfiqul Islam, Lecturer, CSE, DU
Primary memory: RAM
Central storage unit
Volatile
Temporary in nature
Holds operating systems, application programme, data in current use
Other name is (Read/Write) memory
M. Tawfiqul Islam, Lecturer, CSE, DU

17. M. Tawfiqul Islam, Lecturer, CSE, DU
Different types of RAM
S RAM- Exhibits data remanance but still volatile as data dissolves when turn off
D RAM- Data disappears after a certain period automatically if it is not refreshed. This type of RAM needs periodically re-read or re-written. Ex- Z-RAM, TT-RAM, A-RAM
M. Tawfiqul Islam, Lecturer, CSE, DU

18. M. Tawfiqul Islam, Lecturer, CSE, DU
Primary memory: ROM
Proportionally read operation is more than write operation
Contains user programmed instructions like Bootstrap loader
Non-volatile
permanent
M. Tawfiqul Islam, Lecturer, CSE, DU

19. M. Tawfiqul Islam, Lecturer, CSE, DU
Different types of ROM
ROM
Mask ROM
PROM
EPROM
EEPROM
M. Tawfiqul Islam, Lecturer, CSE, DU

20. M. Tawfiqul Islam, Lecturer, CSE, DU
Secondary memory
Auxiliary unit
Storing capacity is huge
Normally non-volatile
Normally two types-
Magnetic
Optical
M. Tawfiqul Islam, Lecturer, CSE, DU

21. Secondary memory: Magnetic
Variation of ‘Magnet polarity’ determines whether the bit will be 0 or 1
Data write process is done by electromagnetic head
Ex- hard disk, floppy disk, magnetic tape
M. Tawfiqul Islam, Lecturer, CSE, DU

22. Secondary memory: Optical
Variation of light reflection determines the nature of bits
Data is written with the help of LASER or UV rays
Ex-CD-R/RW, DVD-R/RW, BD-R
M. Tawfiqul Islam, Lecturer, CSE, DU

23. M. Tawfiqul Islam, Lecturer, CSE, DU
Memory address:
It is a number or a set of digital number (bit/Bytes) in the memory
This address specially represented by binary numbers
Decimal, Octal, Hex-decimal numbers are also used for addressing
M. Tawfiqul Islam, Lecturer, CSE, DU

24. M. Tawfiqul Islam, Lecturer, CSE, DU
Virtual memory:
When secondary memory is used as primary memory then this is called virtual
Provide assistance to the RAM, by creating space for the great amount of data
When RAM finishes it’s access, virtual memory vanishes
Virtual memory can be selected by user
M. Tawfiqul Islam, Lecturer, CSE, DU

25. M. Tawfiqul Islam, Lecturer, CSE, DU
Cache memory:
Small memory chip is attached between CPU & main memory
Give the assistance to the resisters
Speed up the data process
Three types of cache memory is found e.g. L1(CPU resident), L2 & L3 (mother board)
M. Tawfiqul Islam, Lecturer, CSE, DU

26. M. Tawfiqul Islam, Lecturer, CSE, DU
Resisters
They are not the part of main memory but store data and pass as directed by CPU
The size of the resisters which is sometimes called the word size,indicates the amount of data with which CPU can work/access.
Ex- 32 bits processor means, 04 bytes data processing capability
M. Tawfiqul Islam, Lecturer, CSE, DU

27. Question...???