Computer System Units and Data Encoding

System Unit Types

• Slate Tablet PC - A monitor attached to the system unit, lacking an integrated keyboard. Uses a mobile OS, accepts gesture input, and displays content primarily.
• Handheld Computer System Units - Include personal digital assistants (PDAs) and smartphones that contain electronic components, secondary storage, and input/output devices.
• Palm Computers - Contain a complete computer system.

Data Representation & Encoding

• Data and instructions are represented electronically using digital signals.
• Digital signals are electrical and have an on/off state, unlike analog signals, which are continuous.
• The Binary System uses 0 and 1 as digits. Each 0 or 1 is a bit (binary digit).
• Bytes are groups of eight bits and represent one character.

Character Coding Schemes

• ASCII (American Standard Code for Information Interchange) - A common coding scheme.
• EBCDIC (Extended Binary Coded Decimal Interchange Code) - Primarily used for mainframe and super computers.
• Unicode - Handles languages with a large number of characters.

System Board

• Also known as the main board or motherboard, it controls communication between components.
• Components connect to the system board.
• Data path - Traffic monitor.

System Board Components

• Sockets - Connection points for chips.
• Chips - Tiny circuit boards etched onto squares of silicon. Also known as silicon chips, semiconductors, or integrated circuits. They are mounted on carrier packages.
• Slots - Provide connection points for specialized cards or circuit boards.
• Bus lines - Pathways that support communication among electronic components.

Microprocessor

• The Central Processing Unit (CPU) is located on the microprocessor chip and acts as the brain of the computer.
• Two Basic Components
  • Control Unit - Directs program instructions, flow between memory and ALU, and flow between CPU and I/O devices.
  • Arithmetic-logic unit (ALU) - Performs arithmetic and logical operations. It also holds data, instructions, and information.

RAM

• Random Access Memory (RAM) holds programs and data being currently accessed by the CPU.
• Volatile - Data is emptied when power is shut off.
• Flash RAM - Can retain data even when power is disrupted and is used in high-end portable computers.
• Cache memory - Improves processing by acting as a temporary high-speed holding area between the memory and CPU. It holds frequently accessed information for faster processing.

RAM Types

• Flash memory - Retains data even if power is disrupted. It is the most expensive type of RAM and is used in digital telephones, digital video cameras, and portable computers.
• Virtual Memory - Large programs are divided into parts and stored on a secondary device (usually a hard disk).

Expansion Buses

• Connect the CPU to other components and slots on the system board.
• Universal Serial Bus (USB) - Connects external USB devices.
• FireWire - Similar to USB but more specialized, used with audio and video equipment.
• PCI Express (PCIe) - A dedicated path for each connected device.

Ports

• Sockets for connecting external devices.
• Ports can connect directly to the system board or connect to cards inserted into slots.

Types of Ports

• Standard Ports - Examples include VGA, DVI, USB, FireWire, and Ethernet.
• Specialized Ports - Examples include S/PDIF (Sony/Philips Digital Interconnect Format), HDMI (High Definition Multimedia Interface), and MIDI (Musical Instrument Digital Interface).
• Legacy Ports - Older types of ports, mostly replaced by faster, more flexible ports like USB. Examples include serial ports, parallel ports, keyboard and mouse ports, IrDA, and game ports.

Cables

• Connect external devices to the system unit through ports.
• One end connects to the device, and the other end has a connector that matches the port.

Power Supply

• Computers require direct current (DC).
• DC power is provided by converting alternating current (AC) from wall outlets or batteries.
• Desktop computers use power supply units.
• Notebooks and handhelds use AC adapters.