ASCII vs UNICODE

ASCII

American Standard Code for Information Interchange

7 bit code is 128 characters

Extended 8 bit ascii -  256 characters

 

UNICODE

16 bit -  65,536 characters (2^16)

 

+ allows us to represent more world languages like Chinese, Japanese etc

 

-        It takes more memory per character

UNICODE has ASCII included in it at the exact same places i.e 65 in ASCII and 65 in UNICODE give A!!!!!

ASCII Vs UNICODE

Test

ASCII and UNICODE

Floating Point Posseeeee!

Floating Point Representation

Allows us to represent decimals (real numbers)

Mantissa represents the actual number

Exponent tells you how far to "slide/float" the decimal place (from the front)

NIGHTMARE!!!!

Mantissa affects the ACCURACY!!

Exponent affects the RANGE!!

Signed Bit Vs Two's Complement

Both of these allow us to represent negative (and positive numbers)

Signed bit uses the first "bit" to indicate positive or negative

i.e 1 0 0 0 0 0 0 1 = - 1 (we disregard the first bit after finding out its sign)


this gives us a few problems

first, we lose RANGE, for an 8 bit number we can only represent 2 ^ 7 numbers (because we chucked a bit away)

You may also have noticed that there are two zeros

1 0 0 0 0 0 0 0 = negative zero
0 0 0 0 0 0 0 0 = postitive zero


Two's Complement works similarly, the first digit tells you positive or negative.

If its a 1 (negative) we invert the number and add one
If its positive we treat it like a normal binary number

Why computers use the Binary Numbering System!

Computer Systems are two state ( ON and OFF)

Binary Numbering are also two state ( 0 and 1)
The two states can be represented by 1 and 0.

Disadvantages???
Difficult to understand, error check ..

Advantages???
+ Easy to store in Backing Storage
+ Not affected by voltage degredation
+ Less rules of addition (and multiplication etc)

Peripherals

Puppy Dogs Bite Very Hard

Functions of the Interface (The hardware and Software required to communicate between the Hardware (peripherals) and the processor

Protocol conversion (odd and even parity)
Data Format Conversion (Analogue to digital and visa versa)
Buffering (Temporary Data Storage)
Voltage Conversion (components of motherboard work at lower voltages to peripherals)
Handling of Status Signals (Ready, Out of Ink, Paper Jam)

Solid state storage devices have no moving parts, require less energy are more robust, are physically smaller and more robust.

Buffering - hardware solution, built into peripherals like printer
spooling (also temporary data storage) is the software solution that uses fast backing storage to send data to peripheral at rate it can cope with

Interface speeds are increasing USB 1 - 2 - 3 increased data transfer rates

Backing Storage devices

Smaller Physically, increased capacity, faster data transfer speeds and becoming cheaper per bit storage