Logic Circuits

Logic Circuits 

What are logic gates?

Logic Gates are very small electronic decisions-making devices that are fed one or more inputs and give back one output. 

There are 3 basic logic gates:

• the NOT gate
• the AND gate 
• the OR gate

What are truth tables?

A truth table is used to define the output of a logic gate or a logic circuit for all possible combinations of inputs. 

The And,Or and Not Gate.

Not Gate

And Gate

Or Gate

Computer Logic (part.2)

Where we were last time :
So there is the BINARY and the DECIMAL
So lets say we want to convert from binary to decimal
and
from decimal to binary



Binary to Decimal

We have the number 1001 base 2

8 4 2 1
1 0 0 1
8+1=9
1001 base 2 - 9 base 10

Decimal to Binary

9 base 10

8 4 2 1
1 0 0 1
9 base 10 - 1001 base 2

There is hexadecimal too !
It's base is 16
It has 15 numbers but with a difference -
1
2
3
4
5
6
7
8
9
10-A
11-B
12-C
13-D
14-E
15-F

Convert Binary to Hexadecimal 


011010 base 2 - 1A base 16
8421  8421
0001  1010
1         8+2=10

Convert Hexadecimal to Binary 

1A base 16 - 00011010 base 2

1    A (10)           Working
0001 1010          8 4 2 1
                            0 0 0 1
                                     
                            8 4 2 1
                            1 0 1 0          


Convert Decimal to Hexadecimal

27 base 10 - 1B bas 16
Convert to Binary
16 8 4 2 1
1   1 0  1 1
Convert to hexadecimal 
8 4 2 1   8 4 2 1  
0 0 0 1   1 0 1 1
1             8+2+1=11


Convert Hexadecimal to Decimal

A1 base 16 - 10100001 base 10
Convert to Binary 
A        1
1010    0001
10100001 base 2
Convert to decimal
 128 64 32 16 8 4 2 1
  1     0   1   0  0  0 0 1

A. Converting BINARY TO DECIMAL 
B. Converting DECIMAL TO BINARY 
C.Converting BINARY TO HEXADECIMAL
D.Converting HEXADECIMAL TO BINARY
E.Converting DECIMAL TO HEXADECIMAL
F.Converting HEXADECIMAL TO DECIMAL

Representations of Characters 

Besides numbers, characters are also used in everyday life to express information. This means that characters also have to be represented in binary using a unique binary code. This is called the character code.

ASCII 
ASCII ( American Standard Code for Information Interchange) is an 8-bit code used to represent characters in binary.

Unicode 
Unicode by using 16 bits to represent each character. These 16 bit binary numbers allow 2 base 16 different combinations to be represented, which gives us a system that can encode up to 65,535 different characters. For the moment at least, this system should suit purposes.

Analogue and Digital data

Analogue - An analogue device is one in which data is represented by some quantity which is continuously changing.


Digital Data - Digital data is a device that shows data at discrete intervals.





Modem (MODulator - DEModulator)

To convert between the analogue signals used in telephone cables and digital signals used by a computer

Sound Card
A sound card is needed to output for music or speech from programs.

Network Card
A network card lets computer communicate with other computers that are networked together.

Computer Logic (part 1)

What is a 2-state device??

A  2-state device is like a switch on the wall, it can be only one of two possible states at any given time. i.e it may be either ON or OFF


Binary

Binary is a number system. It is the ideal number system to represent two-state device because it has only two digits : O ,  1 . It is imp. to notice that in the number system we use everyday life (called decimal system) ten digits are used: 0,1,2,3,4,5,6,7,8,9.

Binary, then, with its 0s and 1s, is a very convenient method of representing the two internal states of a computer's electronic components. Binary digits do not actually exist inside computers, only electrical charges. So, for example +5 volts can be represented by binary 1 and the absence of charge (zero volts) by binary 0.


Bit - stores 0 , 1
Byte - 8 bits = 1 character
Kilobyte-1024 byte
Megabyte- 1024 x 1024
Gigabyte - 1024 x 1024 x 1024
Terabyte - 1024 x 1024 x 1024 x 1024

So there is the BINARY the DECIMAL
So lets say we want to convert from binary to decimal
and
from decimal to binary


Continue in the next part..... :)

WordProcessing

Functions of a Word Processor

Columns

Columns are mainly used in newspapers and magazines. Column capability wraps words to the next line within each column. Magazine-style columns flow words from the bottom of one column to the top of the next.

Mail Merge

Mail merge is used to create personalised letters by combining together a form letter and a list of data ( that may include names, addresses etc.. )

Table of Contents

A table of contents is a list of the headings in a documents. You can use a table of contents to get an overview of the topics discussed in a document.

Indexes 

An index lists the terms and topics discussed in a document, along with the pages they appear on.

A few last things in Chapter 1

Main Components of a computer




The Central Processing Unit (CPU) and the Main Memory (RAM and ROM) are found in the system unit.

The CPU is the brain of the computer, it governs the overall speed of your computer.


The Main Memory is a part of a computer system where data instructions are held for use by the CPU and where the CPU puts results it generates.


There are three types of buses that are always going from the CPU to the Main Memory(RAM and ROM) These are :

1. Address Bus
2. Data Bus
3. Control Bus

 A bus is a set of parallel wires connecting two or more components of a computer.

Practical -Utilities

Formatting a Diskette 
When you format a disk, you divide the disk into areas tracks and sectors. 

How to format a disk?
- Insert the disk into the floppy drive
- Double click on My computer
- Right click on the drive you want to format
- Select format from the menu
- Choose full option. You may choose quick disk that has already been used, but it does not check the disk for errors and so is not generally recommend.
-Enter a label for your disk if you wish.
-If the disk will be used to boot you pc, check the box marked ' Copy system files' to format the disk as bootable.
- Click Start button.
- View the results to make sure the disk was properly formatted.

What do Scan disk do?
 Scan disk checks your disk for any errors of faults.

What is Defragmentation?
The Disk Defragmenter rearranges the files and free space on your disk so that files are opened more quickly because they are stored in adjacent (next to each other) units and free space is consolidated.

How to start a Defrag?  
- Click Start
-Point to Programs
- Point to Accessories
- Point to System Tools
- Click Disk Defragmenter

Win zip / Compressed Folders 
Folders that are compressed using the Compressed (zipped) Folders feature use less space and can be transferred to other computers more quickly. 

Virus and Antivirus 

What is a computer virus?
It is a program that disrupts the normal operation of a computer. It is created intentionally to cause harm.
What is an antivirus?
An antivirus software serves to protect your computer from viruses. However it always needs updates to protect your computer from the latests viruses.
 

The First Chapter

The Computer System 


Did you know that DATA+STRUCTURE=INFORMATION !


What is a computer ?

A computer is a device that accepts input, processes data, stores data and produces output .

What is an Input?
An Input is the process entering into the computer. The most common input is the keyboard.

What is Soft copy and Hard copy?
Soft copy-  It is the data displayed on a monitor screen.
Hard copy- The data printed on a paper.

What are supercomputers , Mainframe , Microcomputers , Desktop Computer , Portable Computers?

Supercomputers - Supercomputers are very powerful and have a lot of memory .... Infect NASA is  using Supercomputers.
Mainframe - They are less powerful than supercomputer but :
They are very fast
They have large-capacity
And also occupying specially wired and conditioned rooms.
Desktop Computers - They are the type of computers they usually we use at home... These machines run comparatively easy-to-use application software.
Portable Computers - Most known as laptops or net book, small enough and light enough to move easily from one place to another.

What is the difference between system software and application software?  
The system software is the operating system we are running on ex. Windows XP.
Application Software is the kind of software we use to preform a general-purpose task.