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TOPIC 4: INSIDE THE COMPUTER - PROCESSING AND MEMORY - Coggle Diagram
TOPIC 4: INSIDE THE COMPUTER - PROCESSING AND MEMORY
Data Representation
How do Computers Represent Data?
Analog signals are continuous and vary in strength & quality.
Recognize only two discrete states: on or off (binary system)
Use number system with two unique digits: 0 and 1 called bits (short for binary digits)
Byte
Eight bits grouped together as a unit.
Provides enough different combinations of 0s and 1s to represent 256 individual characters, number, uppercase and lowercase letters, punctuation marks.
8-bit byte for the letter E: 0 1 0 0 0 1 0 1
8-bit byte for the symbol * : 0 0 1 0 1 0 1 0
8-bit byte for the number 6 : 0 0 1 1 0 1 1 0
3 Popular Coding Systems
ASCII American Standard Code for Information Interchange (most commonly used)
EBCDIS Extender Binary Coded Decimal Interchange Code
Unicode - coding scheme capable of representing all world's languages
Step 1:
The user presses the capital letter D (shift + D key) on keyboard.
Step 2:
An electronic signal for the capital letter D is sent to the system unit.
Step 3:
The signal for the capital letter D is converted to it ASCII binary code (01000100) and is store in memory for processing.
Step 4:
After processing, the binary code for the capital letter D is converted to an image, and displayed on the output device.
Memory
Electronic components (holding area) that store instructions, data and information.
Like motherboard, memory is contained on chips connected to the system board.
Memory consists of electronic components that store instructions waiting to be executed by the processor, data needed by those instructions and the results of processing the data.
Basic categories stored
the operating system and other programs
applications
data being processed and the result information
Types of memories
Volatile memory
loses its contents when power is turned off
example include Random Access Memory (RAM)
Nonvolatile memory
does not lose contents when power is removed
examples include Read Only Memory (ROM), flash memory and Complementary Metal Oxide Semiconductor (CMOS)
Each byte resides temporarily in a location in memory that has an
address
Memory size commonly is measured in gigabytes (GB)
Common types of RAM
Dynamic RAM (DRAM)
Synchronous DRAM
(SDRAM)
synchronized to the system clock
much faster than DRAM
DDR SDRAM (Double
Data Rate SDRAM)
transfer data twice, instead of once, for each clock cycle
faster than SDRAM
DDR2
second generation of DDR
faster than DDR
DDR3
designed for computers with multi-core processors
faster than DDR2
third generation of DDR
DDR4
fourth generation of DDR
faster than DDR 3
Rambus DRAM (RDRAM)
much faster than SDRAM
Static RAM (SRAM)
Memory (cont.)
Cache
Helps speed computer processes by storing frequently used instructions and data.
Memory cache speeds the processes of the computer because it stores used instructions and data.
How much RAM do you need?
Depends on type of applications you intend to run on your computer.
Flash memory can be erased
electronically and rewritten.
CMOS technology uses battery
power to retain information when the power to the computer is off.
Busses
Data bus
pass information in bi-directional
Address bus
transmits signals for locating a given address in primary storage, indicating where data should be placed.
Control bus
transmits signal specifying whether to read or write data to or from primary storage address, input device or input device.
Memory (cont.)
Access Time
Terminology
Millisecond (ms): One-thousandth of a second
Microsecond (µs): One-millionth of a second
Nanosecond (ns): One-billionth of a second
Picosecond (ps): One-trillionth of a second
RAM vs ROM
RAM
random access memory
volatile
can be written to and erased
SRAM-static RAM
DRAM-Dynamin RAM
SDRAM and RDRAM
comes on SIMMs and DIMMs
ROM
read only memory
permanently recorded data
things such as boot routine are stored in ROM
nonvolatile
some ROM chips, called PROM are programmable with a ROM burner