S2 Computer Literacy Computer Hardware Overview of Computer Hardware Motherboard CPU RAM Harddisk CD-ROM Floppy Disk Display Card Sound Card LAN Card Motherboard It is the main circuit board that links all the hardware components together. There are many chips or IC (Integrated Circuit) on the motherboard which contains millions of transistors. CPU (Central Processing Unit) It interprets and performs instructions of a computer program. The most determining factor in how powerful a computer is. A CPU in a common PC system is known as the microprocessor. A model of Computer CPU A CPU consists of two parts, the ALU and the CU. Both the ALU and the CU contains registers, which are high-speed memory temporarily hold data and instructions during processing. Different kind of CPU Intel Celeron Pentium 4 Xeon AMD Duron Athlon XP Sempron Athlon 64 Common features Clock rate > 2GHz Differences Word Size Cache Memory Size Front Side Bus No. of transistors RAM RAM – Random Access Memory RAM is volatile data is lost when the power to the computer is turned off The instructions and data for the job performing are written to RAM and read from it as needed. Secondary Storage CPU can only process data in RAM But RAM is volatile, processed data cannot be stored in RAM Secondary Storage device is needed It is a non-volatile storage media which has a big storage size. Secondary Storage Magnetic Media - Floppy Floppy 1.44 MB Plastic disk with magnetic coating Reading and writing speed is slow Data easily lost Some new kind of floppy called SuperDisk and ZipDisk have larger capacity, but need special drives to read the disk Magnetic Media – Hard disk Hard disk Huge storage capacity A set of circular metal plates with magnetic coating Read/write head inside Rotate at a very high speed for faster data access Magnetic Media – Hard disk Inside the Hard disk Optical Media - CD CD – Compact Disk, using laser technology Normally it can store 640MB data. It is cheap and durable. Data is stored by "burning" pits and lands on the metal coating. A laser beam is projected to the disc surface and the reflection will be read to detect the patterns of pits and lands. Optical Media - CD The way CD read data The way CD drive rotate the disc Optical Media – CD-R/CD-RW CD-R (CD Recordable) and CD-RW (CD Rewriteable) Both of them allow users to write data onto a CD-R or CD-RW disc. CD-R can be written only once CD-RW can be write and overwritten for many times. Optical Media – DVD-ROM It is similar to CD-ROM but its capacity varied from 4.7GB to 17GB. A DVD-ROM drive is needed to read data from a DVD-ROM. As its capacity is large, film companies use them to publish high quality film. Optical Media – DVD R/DVD RW It is similar to CD-R and CD-RW, but has a much higher capacity. There are different standard DVD+R, DVD-R DVD+RW, DVD-RW DVD-RAM Different disc drives and different discs are not compatible Most DVD writers support RW standard DVD-R, DVD-RW seems to be the most popular standard Semi-conducting Media It is sometimes called flash memory, where it uses semi-conductor chips to store data. No mechanical movement involved in data transfer, so it is: Quiet in operation Not easy to be damaged Used in portable devices such as: PDA (Personal Digital Assistant) MP3 player Digital camera Semi-conduction Media CF card Flash Thumb Drive SD card Card Reader Memory Stick Measuring Secondary Storage device Access time The average time it takes the device to locate data on the storage medium and read it. Lower access time indicates higher speed. The unit is usually in ms. Measuring Secondary Storage device Data Transfer Rate The amount of data that a storage device can move from the storage medium to the computer per second. Higher data transfer rate indicates higher speed. The unit is usually measured in MB/s. Measuring Secondary Storage device Storage Capacity It is the maximum amount of data that can be stored on a storage medium. The unit is usually measured in KB, MB, and GB. Measuring Secondary Storage device Input Device An input device is any hardware that allows a user to enter data and commands into a computer. Input Device – Touch Screen A pressure sensitive display that allows users to select options with fingers or stylus. Not designed for inputting large amount of text. It is often used in information kiosk, PDA and tablet PC. Scanner Just like a photocopier, it sends bright light on the document and detects the light reflected from the source document. The data detected are converted into a digital graphics. Barcode Reader Books in library and goods in supermarket are given a unique bar code. A bar code reader will be used for check out. It is highly accurate and fast. Voice Input A user can use a microphone to input sound into a computer. A technology called voice recognition can be applied to analyze the speech into text. Output Device An output device is a hardware that presents digital information in a form that human being can understand. Output Device – CRT Monitor It is heavy and occupies a lot of desk space. Output Device – LCD Monitor LCD monitors are thinner in size but more expensive than CRT monitor. Notebook computer, tablet PC have an integrated LCD monitor. Output Device – Inkjet Printer It sprays tiny ink drops onto paper from an ink-filled print cartridge. It can produce low-cost colour printout. Output – Laser Printer a laser beam to produce an electronicallycharged image on a drum, causing toner to stick to the drum whether the laser hits. toner is transferred to the paper as the drum presses against it and a heating process follows which fixes the toner onto the paper. This technology is similar to that used in a photocopying machine.