Computer Systems I m ONLY a machine Standard Grade

Computer Systems I’m ONLY a machine! Standard Grade Revision

Hardware • Hardware refers to all the parts of the Computer System that we can touch. • An item of hardware is called a device. Microprocessor Main memory Input / Output Backing Storage

Central Processing Unit Input CPU RAM ROM Backing Storage Output

The Processor • Carries out the actual process • Follows a set of instructions called a program

Representing Graphics & Text • Bit-Mapped Graphics – Dots called pixels – Each pixels is either • On (1 – black) or Off (0 – white) • Text – ASCII standard file format – 01001101010100101010000001010000001001010010000001010101001 0010101010100 = MUJTABA BE QUIET

Units of Storage Binary Unit Value Bit 1 or 0 Byte 8 bits Kilobyte (KB) 1024 bytes Megabyte (MB) 1024 Kilobytes Gigabyte (GB) 1024 Megabytes Terabyte (TB) 1024 Gigabytes

Main Memory Input CPU RAM ROM Backing Storage Output

Main Memory • Where the computer stores programs & data • Types: – RAM • Random Access Memory – ROM • Read Only Memory

Main Memory • ROM Chip – Permanent storage – Data is safe when computer is switched off – Data can not be added to ROM – Some OS are stored on ROM Chips • RAM Chip – Temporary storage – Data is lost when computer switched off – Data can be written to RAM – Upgrading is easy with RAM Chips

Input CPU RAM ROM Backing Storage Output

Input Devices (Navigational) • Mouse • Trackball • Track pad • Touch Screen • Joystick • Smart. Board

Input Devices (Data Input) • • Keyboard Graphics Tablet Scanner Digital Still camera • Digital Video Camera • Webcam • Microphone

Backing Storage Input CPU RAM ROM Backing Storage Output

Backing Storage • Method used to physically store data. • Constantly increasing in capacity to meet demands. • Magnetic Storage – Floppy disc, Hard Disc, Magnetic Tape • Optical Storage – CD, DVD • Solid State – USB Flash Drive

Drive or Media Drive Media

Magnetic Storage • Hard Disk Drive – Usually main type of backing store – Non-removable media • Floppy Disk – Plastic disk with rectangular cover – Removable media • Magnetic Tape – Sequential Access – Think VHS tape – Removable media

Optical Storage

Optical Storage • CD-ROM – Read by a laser beam that reflects of surface “pits” and “lands” • DVD-ROM – Similar to CD but with larger capacity because of multiple layers • CD-Recordable (CD-R) / DVD-R – Write Once, Read Many • CD-Rewritable (CD-RW) / DVD-RW – Still uses a laser but contents can be changed

USB Flash Drive • Universal Serial Bus: – Computer interface used by different devices. • Solid State Memory – No moving parts • Advantages – Portable – Can have large memory (currently 8 GB)

Flash Memory Cards • Solid State Memory – No moving parts – Used in cameras and mobile phones • Advantages – Portable – Can have large memory (currently 8 GB) – Can be read by a card reader

Output Input CPU RAM ROM Backing Storage Output

Output Devices • Printer – Laser – Inkjet Comparison of Printers • Resolution – Dots Per Inch (DPI) • Speed – Pages Per Minute (PPM) • Cost – Capital Cost – Running Costs

Output Devices • Plotter • Monitor (VDU) • LCD – Liquid Crystal Display • TFT – Thin Film Transistor • Multimedia Projector • Speakers

Types of Computer • Desktop • Laptop/Notebook • Palmtop

Types of Computer • Mainframe