Classification of computers Types of Computers Based on Generation Based on Size Based on Purpose
Computer Generations First Second Third Fourth Fifth Used vacuum tubes, were large, slow and produced a lot of heat, used machine key and punched cards for storage Used transistors, were smaller, faster and produced less heat, used high level language like Fortran and needed Magnetic tapes for storage Used integrated circuits, were smaller, more reliable, faster and cheaper, used high level languages like BASIC, Operating System introduced Computers of today, uses large scale integration circuits, GUI Uses Artificial Intelligence, accepts instructions or commands through voice and interprets the signal
Computer: Based on Size Mainframe Mini Micro Super Very big and expensive and are used in offices to store large amount of data and to do complex processing Mostly used as a server in a Network, developed to reduce the cost and size Small PCs, laptops, palmtops, uses silicon microprocessor Large computer, cluster of computers to perform complex, scientific calculations Activity Name some leading vendors who manufacture computers
Computer: Based on Purpose Analog Digital Hybrid These are used to work with changing physical quantities. Accepts data as input and records but does not perform any complex calculations on it Mostly used as a server in a Network, developed to reduce the cost and size Small PCs, laptops, palmtops, uses silicon microprocessor Pl tell where these are used? Thermometers, Speedometers, Wrist Watches etc Business applications, Military, Scientific areas etc Pl tell where these are used? Pl tell where these are used? Like ECG machine in a hospital
Computer: Based on Purpose EAI Analog Computer (1964)
Online processing is when processing on the computer takes place immediately as soon as the data is entered. Real time processing is online processing where the data is processed continuously and immediately after it has been captured. Output is immediate. Updation is also prompt. Example? Airways or Railway Reservation, Debit card
Offline processing is when processing on the computer takes place on stored data when required to get an output. Batch Processing is a type of offline processing where data is stored and processed at a later stage. Example? Generation of Electricity Bill
Understanding the Computer System User (HCI) Hardware Software / Instructions / Program Data / Information
Understanding the Computer System The main functions of a computer system are: Input data by user Data capture by the input devices Data processing by software and processor Output information by Output Devices Storage of data on Storage Devices for later use
Computer System User Data Information Software Hardware Input Devices Processor Output Devices Storage Devices
Bar Code Reader
CPU Chipset – CU, ALU, MU
Compact Disc (CD / DVD / VCD)
1. Input data 2. Data Capture 3. Data Processing 4. Outputting information to user 5. Storage of information on storage devices for later use
Translating programs Assembler Interpreter Compiler Helps to translate assembly language into machine language Helps to translate high level language into machine language, one line code at a time Helps to translate high level language into machine language, displays all the errors at one time
During normal operation, the power flows straight through the unit and hence only RFI filtering is usually provided. When the input voltage fails or fluctuates outside of a pre-set tolerance window, the UPS detects this and a relay will close, allowing the UPS to start feeding battery power via the inverter. The inverter is then switched on and either a square, step or sinewave form output is supplied. Upon the return of mains power, the output is switched back onto mains and the inverter is turned off. Typically there will be a break of between 4-10 ms during the transfer to and from the battery mode.
Advantages: Low cost Silent operation (when in standby) Efficient
Disadvantages: Minimal power protection – only protects against a small percentage of problems Poor output voltage regulation – fluctuations such as sags and surges will be passed straight to the load Break transfer to battery mode No failsafe – UPS will drop the load if there is a high start-up current, overload or inverter failure.
A line-interactive UPS operates in a very similar fashion to an offline UPS, except with the advantage of better filtering and output voltage boost/reduce features. Whilst not eliminating mains-borne interference, line-interactive technologies reduce the impact of spikes, surges and sags by ‘clipping’ the peaks and valleys, boosting power or switching to battery back-up. As with offline UPS, when the input voltage fails or fluctuates outside of a pre-set tolerance window, the UPS detects this and a relay will close allowing the UPS to start feeding battery power via the inverter. The inverter, in a good line-interactive UPS, will supply a sinewave output. Upon the return of mains power, the output is switched back onto mains and the inverter is turned off. As with offline UPS, typically there will be a break on the transfer to and from battery mode, though usually this will be shorter than with an offline UPS.
Some manufacturers will try to pass their line-interactive UPS off as online models by calling them ‘digital online’, ‘inline’ or ‘online interactive’ – make sure you know what technology the UPS you are buying actually uses.
Advantages: Lower cost than online Gives better protection than offline Silent operation when in standby Efficient
Disadvantages: Fluctuations, such as spikes, can still be passed straight to the load Break on transfer to battery mode. No failsafe – UPS will drop the load if there is a high start-up current, overload or inverter failure.
Uninterruptible power supplies (UPSs) are devices that maintain the supply of power to a load even when the AC input power is interrupted or disturbed. This is typically accomplished by drawing the necessary power from a stored energy source, such as a battery. UPSs may also convert unregulated input power to voltage and frequency-filtered AC power. Thus, the UPS will provide stable power and minimize the effects of electric power supply disturbances and variations.
UPSs are currently found in commercial, industrial, medical and residential markets. Applications include:
individual computers and computer systems
microprocessor- and microcontroller-based equipment
precision motor-speed applications
mission-critical fields such as telecommunications and Internet nodes
Regular computer cleaning is recommended to prevent overheating and glitches caused by dust inside your CPU. In addition to shorting out electronics, dust can act as an insulating blanket and prevent heat sinks and other componants from cooling off. A few minutes of careful cleaning will remove the computer killing dust from your CPU's fans, heat sinks, electronics and case, allowing the heat to dissipate and cool air to flow unimpeded throughout your system.
For a dust and grime-free CPU and tower we need some computer cleaning supplies: • Anti-static wrist strap or anti-static mat • Soft, lint-free cloth • Canned, compressed air • Mild detergent solution or spray • Q-tips, preferably foam • Computer vacuum (Optional) • CD Drive cleaner disk
How to clean your computer CPU in ten simple steps
STEP ONE - Shut down the CPU and remove the power cord from the electrical outlet.
STEP TWO - Remove the power cord and cables from the rear of your computer.
STEP THREE - Place your computer tower on a stable platform above the floor. A floor’s static charge may damage the computer, even a wood or vinyl floor. It is best to do the cleaning outside the building, or in a maintenance shop due to the air-borne dust created.
STEP FOUR – Clean the outside of the computer case by lightly dampening a cloth with a mild soap solution and wiping off the dust. Use a computer vacuum, if available to remove dust from the fans, air intake and exhaust areas at the rear of the computer.
STEP FIVE - Open the computer case, using a screwdriver if required. If it is unclear how to open it, carefully inspect the rear of the case for screws that may need to be removed. Or, as is the case of some recent Dell computers there are large buttons on the top and bottom of the case that must be depressed before the side of the case swings open (see right). Typically, the left or right side of the case will come off, it will swing open like a hinge, or the main case will lift off its base in a single piece. Consult your owners manual.
STEP SIX – Open the CD ROM drive tray and carefully blow air in, and around the tray to remove dust. Press a paper clip into the tiny hole beneath the CD tray to open it.
STEP SEVEN – Put on an antistatic wrist strap and attach it to an electrical ground, like a metal plumbing fixture or the metal frame of equipment you are servicing (see photo). This will ensure you do not damage sensitive electronics due to static discharge from your body. Alternatively, use an anti-static mat.
STEP EIGHT – Clean the computer inside as well as around fan air intakes and exhaust (see photo) by holding canned air or compressed air at a distance of at least two inches away and blowing away the dust. Clean fan blades, motherboard and other areas. If using canned air, use short puffs. Attack clumps of dirt from different angles to loosen. Take care not to touch anything inside of the case.
This is what the inside of a clean Dell computer looks like:
STEP TEN – Clean cables and power cords while they are disconnected. Lightly dampen a cloth with mild soap solution and gently pull the cables and cords through the cloth. Too tight a grip may damage the cables. Dry the cables and power cords with a dry cloth.