• First generation was Vacuum Tubes
• Transistors changed all that
• Transistors - are essentially a tiny electrically operated switch that can alternate between "on" and "off" many millions of times per second.
• Transistors make up logic gates
• Gates make up Circuits
• Circuits make up the CPU.

• CPU, stands for Central Processing Unit, the "BRAIN" of the computer
• Two parts of the CPU know what both of these do
• Control Unit
• ALU
• The CPU does the instructions the software tells it to do. In order for the CPU to receive the instructions from the programs the programs must me loaded into RAM.
• RAM is also called Main Memory, primary memory or internal memory.
• It's volital memory (short term memory.)

 

• Instruction set of any computer system.
• Registers
• Buses
• The Machine Cycle
• Instruction cycle
• Execution Cycle
• Clock
• Make sure you read about these things and understand what they mean.

• Binary system has two digits: 0 and 1.
• Bit is a Binary digit which is a 0 or a 1.
• The relationship between bit, byte, kilobyte, megabyte, etc. etc. has been talked about a bunch so far. Make sure you know the difference.

Representations

• In RAM (random-access memory) the presence of an electronic charge, or the lack thereof an; electronic charge stands for on or off.
• On disks such as your floppy disks, the states are made possible by the magnetic arrangement of the surface coating ..
• CD Roms are represented by pits, or knicks out of the surface of the disks.
• In fiber optic cable the binary data flows through as pulses of light.
• A very large costs for cable systems and phone companies to replace all there old analog lines with digital.
• So when you hit a key on a computer, inside the computer that keystroke is interpeted as a string of 1's and 0's (e.g. 0110010).

          Look at the figure 4.6 in the book. Those are the binary representations of numbers

• Encoding Systems - these systems combine the bits (0's and 1's) into letters, numbers, and any other special keyboard characters such as "@#$%^%".
• ASCII (AS-key) - American Standard Code for Informatin Interchange
• Based on 7 bits. (100 0001) or a total of seven 0's and 1's.
• It is the most popular encoding system for PC's and data communication.
• Alphanumeric characters - letters, numbers and the special keyboard characters.
• Panel 2.25
• The eighth bit is used for reprsent control characters, ASCII is based on the seven bits.
• ASCII can represent up to 128 characters, all of which are needed for the vast amounts  of "*&^%$#():"{+=-_ " -- those kind of things.
•  There is actually 256 possibilities, but ASCII only uses the 128 characters.
• Extended ASCII contains characters for foreign languages, some companies do have these interpetation capabilities.

• Unicode - 16 bit decoding system. This will be the uniform encoding technique in the future.
• Computers with different languages being typed on the keyboard will be able to communicate much more efficiently.
• There is some conversion problems.
• Space, memory management
• Programs have been written in the 8 bit code, you can't just shut down many programs and fix them then restart them

00000000 = 8 bits = one byte
each digit starting from right to left is equal to a number
The first digit is 2^0 (2 raised to the 0 exponent).
This means if this is the only digit that is represented by a 1 you get
00000001 which is equal to 1 because 2^0 = 1.
The second digit represents 2^1 so
00000010 = 2
The third digit represents 2^2
00000100 = 4
The fourth digit represents 2^3
The fifth digit represents 2^4
The sixth digit represents 2^5
The seventh digit represents 2^6
The last digit represents 2^7
1000000 = 128
1111111 = 128+64+32+16+8+4+2+1 = 255
0111111 = 64+32+16+8+4+2+1=127
127 is how you get 128 representations in ascii code (remember 0000000=0 so 127 and 0 makes
128). Because Ascii doesn't use the last digit.

Why won't word processing software that runs on an Apple Macintosh run on my IBM Compatible
computer?

Machine Language - different instruction sets

• is a binary type programming language that the computer can run directly.

• Incomprehensible to read by most people.

• Consists of 0's and 1's that are instructions unique to each computer architecture.
• Since they are unique to each architecture they won't run on any other architecture.
• The architecture is known as it's PLATFORM.
• If a program or application could run on Macs or Windows machines it would be platform independent.