Truth tables are used to define the output of a logic gate or a logic circuit for all possible combinations of inputs.
The three basic logic gates are : 1) the not gate , 2) the and gate , 3) the or gate.
Monday, 15 April 2013
Logic Gates
Logic gates are very small electronic decision-making hardware devices that are fed one or more inputs and give back one output.
Truth tables are used to define the output of a logic gate or a logic circuit for all possible combinations of inputs.
The three basic logic gates are : 1) the not gate , 2) the and gate , 3) the or gate.
Truth tables are used to define the output of a logic gate or a logic circuit for all possible combinations of inputs.
The three basic logic gates are : 1) the not gate , 2) the and gate , 3) the or gate.
Wednesday, 12 December 2012
Output Devices
Output Devices
An output device has been processed and the computer is giving us feedback.Here is a list of output devices and their meaning.
1) Printer : Printer information is called hard copy. These are needed to compensate for the difference in speeds between the CPU and the printer.
Impact Printers: forms characters and graphics on a piece of paper.
Non-Impact Printers: forms characters on paper without striking the paper.
There are four types of printers : Dot-matrix , Ink-jet printer ,Laser printer and plotter printer.
2) Raster and Vector images : Raster images are not accurate ; they show dots and pixels on the picture. On the other hand vector images are more accurate.
For disabled persons there are braille printers and keyboards , special purpose keyboards , eye sensor readers and speech recognition.
An output device has been processed and the computer is giving us feedback.Here is a list of output devices and their meaning.
1) Printer : Printer information is called hard copy. These are needed to compensate for the difference in speeds between the CPU and the printer.
Impact Printers: forms characters and graphics on a piece of paper.
Non-Impact Printers: forms characters on paper without striking the paper.
There are four types of printers : Dot-matrix , Ink-jet printer ,Laser printer and plotter printer.
2) Raster and Vector images : Raster images are not accurate ; they show dots and pixels on the picture. On the other hand vector images are more accurate.
For disabled persons there are braille printers and keyboards , special purpose keyboards , eye sensor readers and speech recognition.
Input Devices
Input and Output Devices
Input is anything which you enter in the computer. Here is a list of input devices and their meaning :
1) keyboard : It can allow you to enter data in the computer system. Many desktop computers have a numeric keyboard at the side. A standard computer usually has a QWERTY keyboard.
2) mouse : This is a pointing device ; there are three types of a mouse : mechanical mouse , optical mouse and cordless mouse.
3) trackball : This is another pointing device with a ball - mechanism on its top.
4) Joystick : Another pointing device with a vertical leaver on the base.
5) Bar code reader : this uses laser beams to read bar codes.
6) Magnetic ink reader (MICR) : This can read text printed with magnetized ink.
7) Scanner : light-sensing device that converts printed text and graphics into a digital form. There are two types of scanners; a flatbed scanner and a handheld scanner.
8) optical character recognition (OCR) : this device works with word processors and distinguishes characters by the shape.
9) Graphics tablet : This is a flat electronic plastic board for writing or drawing.
10) Optical mark recognition (OCR) : this device can sense circles and rectangles.
11) Light pen : a pointing device that can detect the presence of light.
12) Digital camera : Takes pictures and stores them digitally.
13) handwriting recognition : when you write with your own handwriting on an interactive board and the computer digitally changes your writing to another font.
14) Electronic cards : Used to pay , they store money
Input is anything which you enter in the computer. Here is a list of input devices and their meaning :
1) keyboard : It can allow you to enter data in the computer system. Many desktop computers have a numeric keyboard at the side. A standard computer usually has a QWERTY keyboard.
2) mouse : This is a pointing device ; there are three types of a mouse : mechanical mouse , optical mouse and cordless mouse.
3) trackball : This is another pointing device with a ball - mechanism on its top.
4) Joystick : Another pointing device with a vertical leaver on the base.
5) Bar code reader : this uses laser beams to read bar codes.
6) Magnetic ink reader (MICR) : This can read text printed with magnetized ink.
7) Scanner : light-sensing device that converts printed text and graphics into a digital form. There are two types of scanners; a flatbed scanner and a handheld scanner.
8) optical character recognition (OCR) : this device works with word processors and distinguishes characters by the shape.
9) Graphics tablet : This is a flat electronic plastic board for writing or drawing.
10) Optical mark recognition (OCR) : this device can sense circles and rectangles.
11) Light pen : a pointing device that can detect the presence of light.
12) Digital camera : Takes pictures and stores them digitally.
13) handwriting recognition : when you write with your own handwriting on an interactive board and the computer digitally changes your writing to another font.
14) Electronic cards : Used to pay , they store money
Tuesday, 11 December 2012
Word Processing
Word Processing
Word Processing is used for the creation of text documents. We mainly use microsoft word or word perfect.
The functions of a word processor are :
Word Processing is used for the creation of text documents. We mainly use microsoft word or word perfect.
The functions of a word processor are :
- Text editing
- Word wrap and centering
- Search and replace , Move and copy
- Layout settings
- Headers, Footers and page numbers
- Style sheets
- Clip arts and pictures
- Preview , print and group print
- Footnotes and end notes
- Spelling checker and thesaurus
Style Sheets are the important so i'm going to tell you what their function is.
When you apply a style , you apply the whole group of formats in one simple task. For example instead of taking three steps you can only take 1 by using the Title style , heading 1 and heading 2 .....You can create or view these styles go to the styles and formatting task pane.
Advanced Functions
Mail merge : this is used by combining together a form of letter and a list of data , by that you will create a personalized letter.
Table of contents : This is a list of headings in a document. You can get an over-view of the topics in that particular document
Indexes : This is a list of the terms and topics discussed in a document with the pages they appear on.
*Important to note that both table of contents and indexes are updated automatically.
Monday, 10 December 2012
Computer Logic
Computer Logic
2-state devices also known as bistable devices are like a switch on a wall , it can be only one of two possible states : ON or OFF .
However,computers represent the letters of the alphabet by the binary system .Binary is only 2 numbers : 1 and 2 . With 3 bits we represent 8 characters and with 4 bits we represent 16 characters.
There are also number conversions . You do them by using the LSB ( least significant figure and the MSB ( most significant figure) . When studiying computer studies you should know how to convert these :
2-state devices also known as bistable devices are like a switch on a wall , it can be only one of two possible states : ON or OFF .
However,computers represent the letters of the alphabet by the binary system .Binary is only 2 numbers : 1 and 2 . With 3 bits we represent 8 characters and with 4 bits we represent 16 characters.
There are also number conversions . You do them by using the LSB ( least significant figure and the MSB ( most significant figure) . When studiying computer studies you should know how to convert these :
- converting binary to decimal
- converting decimal to binary
- converting binary to hexa decimal
- converting hexa decimal to binary
- converting decimal to hexa decimal
- converitng hexa decimal to decimal
In a computer we use the representation of characters by the ascii code and the unicode.The ascii code is an 8 bit device and can represent 256 characters. It also has it's limitations.
Ascii stands for : - American Standard Code for Information Interchange.
A bit = 0 or 1
Byte = 8 bits
Kilobyte = 1024 bytes
Megabyte = 1024 kilobytes
Gigabyte = 1024 megabytes
Terabyte = 1024 gigabytes
Analogue and Digital data
An analogue device is one which data is represented by some quantity which is continuously changing , Hence a digital device shows data at discrete intervals.
A modem ( MODulator & DEModulator ) = the purpose is to convert between the analogue signals and the telephone cables and the digital signals used by a computer.
Either than a modem ,network cards and sound cards can also be used.
From analogue to digital is <ADC> & from digital to analogue is <DAC>
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