Communication concepts
Serial transfer transmits data 1 bit at a time through a single line. Parallel transfer transmits more than one bit of data simultaneously using separate lines. Obviously parallel transfer is much quicker than serial transfer because it can send more than one bit at a time. However parallel transfer is only used for distances less than a few metres otherwise errors can occur in transmitting the data and the cabling is too expensive. Serial transmission can be either asynchronous or synchronous. In asynchronous transmission each byte is identified with special stop and start bits. This has become the standard for all personal computers. A party is used to check for errors in transmission requires all data to be sent at the same time
Communication within the computer
A bus is a pathway of wires and connectors that provides the link between the peripheral devices, input, storage, process and output devices. A bus can be though of as a highway on which data control within the computer. This size of the bus is called its width. There are 2 different types of buses:
A part is a socket to connect peripheral devices, it is usually located at the rear of the system unit. Parts are either parallel or serial.
- An internal bus is located on the motherboard and links the CPU and memory. These buses are photochemically edited layers of metal that create electrical channels
- An expansion bus connects peripheral devices to the CPU and memory. If the expansion bus connects directly to the CPU and bypasses RAM it is called a local bus. There are different types of buses, such as ISA, EISA, VESA AND PCI.
A part is a socket to connect peripheral devices, it is usually located at the rear of the system unit. Parts are either parallel or serial.
- Parallel parts transmit 8 bits(1 byte) at a time along an 8 parallel line. They are used to connect devices that send and receive large amounts of data such as printers and disk drives
- Serial parts transmit data one bit at a time using only one communication line. Serial parts are often called COM or communications parts and assigned a number such as COMI and CONZ. Serial parts connect any peripheral device, such as a mouse, keyboard, modem or plotter
modem
A modem is a device that enables data to be transmitted from one computer to another. The word modem stands for modulator/demodulator. A modem converts digital signals sent from a computer into analogue signals suitable for transmission along a telephone line. Analogues systems are pulses in the form of waves. Depending on the modem uses, they can be electrical pules or light pulses. When the signal is received by another modem, it reverses the process by converting the analogue signal into a digital signal suitable for the receiving computer
networks
When a number of computers(or terminals) and their peripheral devices are connected it is called a network. The devices used to send data to a computer system or receive data from a processor called terminals. Terminals can either be smart or intelligent or dumb
Local Area Networks(LAN'S) connect computers or terminals within a building or group of buildings on one site. There are 3 advantages of using a LAN.
Wide Area Networks(WAN's) connect computers over hundred or thousands of kilometres. WAN's rely on links such as coaxial cables, fibre optic cables and microwave devices
- Smart terminals can be done same low-level processing such as text editing
- Intelligent terminals have both memory and processing capabilities
- Dumb terminals do not contain a processor and consist of keyboards and monitors
Local Area Networks(LAN'S) connect computers or terminals within a building or group of buildings on one site. There are 3 advantages of using a LAN.
- They allow limited hardware resources such as printers, hard disks and modems to be shared
- They allow application software to be shared
- They improve communication among users on the network by allows messages to be sent and received
Wide Area Networks(WAN's) connect computers over hundred or thousands of kilometres. WAN's rely on links such as coaxial cables, fibre optic cables and microwave devices