Instructions are translated to machine code. In some architecture, all machine code instructions are the same length i.e. fixed length.
In other architectures, different instructions may be translated into variable lengths in machine code. Complex Instruction Set Computer (CISC): If the control unit contains a number of micro-electronic circuitry to generate a set of control signals and each micro-circuitry is activated by a micro-code, this design approach is called CISC design.
In this Variable length instructions are commonly used and less space is required. Reduced Instruction Set Computer (RISC): To execute each instruction, if there is separate electronic circuitry in the control unit, which produces all the necessary signals, this approach of the design of the control section of the processor is called RISC design. In this Fixed length instructions are commonly used so job of fetching & decoding instructions is more efficient.
Chapter 3 Topic 19 Protocols: Protocols are software that performs a variety of actions necessary for data transmission between computers. Protocols are a set of rules for inter-computer communication that have been agreed upon and implemented by many vendors.
Network protocols which are essentially software are sets of rules forCommunicating timings, sequencing, formatting, and error checking for data transmission. Providing standards for data communication. A protocol defines the following three aspects of digital communication: Aspect Description Syntax Syntax means the format of data being exchanged.
It includes the character set used, type of encoding scheme, etc.
Semantics Semantics means the type and order of messages used to ensure reliable and errorfree information transfer.
Timing Timings define the rate of data transmission or the speed and the correct timing for data transfer. Different protocols cannot talk to each other hence standard protocols have been structured to resolve the problem.
Network transmission over internet is not actually continuous but is carried out in packets. The entire operation of data transmission over a network is broken down into several systematic steps.
Each step has its own rules or protocol. We are now discussing this process in brief.
When transmission begins, Protocol at the sending computer:
– Breaks the data into packets,
– Adds destination address (of the other computer/server) to the packet,
– Prepares and sends data for transmission through Network Interface Card (NIC).
After transmission from sending device, Protocol at the receiving computer–
– Takes data packets off the cable or other medium,
– Brings packets into computer through Network Interface Card (NIC),
– Strips the packets off any transmitting information like address,
– Copies data from packet to a buffer for reassembly,
– Passes the reassembled data to the application program say Internet Explorer.
TO FULL EBOOK CLICK BELOW DOWNLOAD LINK
CLICK HERE TO DOWNLOAD PDF FILE OF IPCC IT CHANGES