Dot Matrix Print Head

• Impact printer
• Print head strikes inked ribbon
• Line printers
• Band printers
• Speed measured in characters per second

Ink-jet printers

• Non-impact printer
• Inexpensive home printer
• Color output common using CMYK
• Cyan, magenta, yellow, black
• Sprays ink onto paper
• Speed measured in pages per minute
• Quality expressed as dots per

Definition of memory and its classification

Memory Hierarchies

Definition of memory and its

classification

Ø Memory

• When you launch a program, it is loaded into and run from memory

Ø Classification of Memory

Ø Internal Processor Memory

Ø Main Memory:

Example: RAM, ROM.

Ø Secondary Memory:

Example: CD, Floppy etc.

Memory Capacity

ü Bit

ü Byte: 1 byte= 8 bits

ü Kilobyte (K or KB): 1KB=1024 bytes

ü Megabyte (M or MB): 1MB=1048579 bytes

ü Gigabyte (G or GB): 1GB=1048876 byte

ü Terabyte

Memory Hierarchies

General Properties of Memory Devices

• Access Time: The average time required to read a fixed amount of information from the memory

• Cycle time: The minimum time between two consecutive memory access operations is called the cycle time.

• Data Transfer rate: The maximum amount of information that can be transferred to or from the memory every second is called the data transfer rate.

Main memory or Primary memory

Main memory or Primary memory

Ø Read only Memory

Ø Random Access Memory

Ø Cache Memory

Read only Memory (ROM)

• Read Only Memory.
• Used for storing programs & data permanently.
• User may read data from ROM but may not write on ROM.
• Permanent or Nonvolatile memory

Random Access Memory (RAM)

Ø Temporary storage that can be read from or written into by the user.

Ø Used primarily to store user programs and data.

Ø Temporary or Volatile memory.

Ø Determines a computer’s speed and power

Ø 2 types of RAM:

Static RAM

Dynamic RAM

Differences between SRAM and DRAM

SRAM	DRAM
High speed RAM	Relatively slower
SRAM is costly	Less costly
Does not require refreshing	Requires refreshing periodically
Generally used for cache	Used for main memory

Difference between RAM & ROM

RAM	ROM
Random Access Memory	Read Only memory
User can read & write into it	User can only read from it
For any type of processing, user must store program & data into RAM	Manufacturer stores instruction into ROM permanently
Temporary or volatile memory	Permanent or non-volatile memory