HARDWARE & DATA TRANSMISSION

HARDWARE & DATA TRANSMISSION

1. HARDWARE ON A COMPUTER

   • Hard Drives Floppy Drive DVD / CD Rom Power Supply Memory (RAM) Motherboard Central Processing Unit (CPU)
     • WHATS (CPU)?
       • CENTRAL PROCCESING UNIT
         • Arithmetic LOGIC UNIT
           • ALU : Performs two sorts of operations on data 1) Arithmetic operations (addition, subtractions, multiplication, division) 2) Logical operations (comparing one data item to another, is it smaller, greater, equal to) 3) Acts as a conduit through which all I/O to computer is done (Gateway to the processor)
         • CONTROL UNIT
           • Control Unit : Co-ordinates and controls all the operations carried out by the computer. It operates by repeating three operations: 1) FETCH – causes the next instruction to be fetched from main memory 2) DECODE – produces signals which control the other parts of the computer such as the ALU. 3) EXECUTE – causes the instruction to be executed.
         • Program Counter : Holds the address of the next instruction to be executed. It is also known as the sequence control register (SCR) or the sequence register.
         • Memory Address Register : Holds the position / address in memory of the location containing either: The next piece of data to be read or The next instruction to be used
           • Accumulator : The accumulator or “General Purpose Registers” as they are often called are used for performing arithmetic functions.
         • Memory Data Register : The contents of the address specified in the MAR are copied to the MDR. This may be either: An instruction / operation or The data to be used (with an instruction) or Data to be copied to an address
         • Current Instruction Register : Holds the instruction while it is being decoded/executed. The contents of the MDR are copied to the CIR if it is an instruction. Contains the operator and the operand of the current instruction
         • Status Register : Contains “status” bits or flags that are set or cleared based on the result of an instruction.
     • MEMORY UNIT?
       • RAM
       • rom/read only memory
         • Non-volatile memory, its contents are permanently etched into the memory chip at the manufacturing stage.

2. BUSSES...

   • Buses: A bus is a set of parallel wires connecting two or more components of the computer.
     • ADDRESS
       • Address Bus: communicates the physical addresses of computer memory elements/locations that the requesting device wants to access (read/write).
     • CONTROL
       • Control Bus: the control bus carries command and control signals to and from every single connected device
     • DATA
       • Data Bus: this bus transport the actual physical data, the bits and bytes of information to and from the memory

3. DEVICE CONNECTIVITY

   • Device can be connected to a computer either by physical wiring “hard wire” (physical) or by some kind of remote connection “wireless” (non-physical).
     • so types of physical connections
       • twisted pair
       • fibre optic
       • copper coaxial

4. transmission

   • measured in bits per second
     • i.e 8mbps meaning 8 megabits per second

5. SECONDARY STORAGE MEDIA

   • Solid State : Data is recorded onto solid state memory chips. Very durable and fast, no mechanical moving parts needed.
   • Optical : Data is recorded onto optical disks. Lasers read and write data. Highly portable.
   • Magnetic : Data recorded onto magnetic disks. Mechanical parts move over the disks surface to read and write data.

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