• Fetch the instruction – the processor fetches the instruction from a memory address stored in a program counter and transfers the instruction, via a data bus, to an instruction register. At the end of the fetch operation, the counter points to the next instruction that will be read in the next cycle.
• Decode the instruction – the processor decodes the instruction stored in the instruction register, including getting any operands required to complete the instruction.
• Execute the instruction – the decoded instruction is executed.
• Store the result – the result generated by the execute phase is stored in the main memory, and/or sent to an output device. The program counter is updated with feedback from the arithmetic logic unit (ALU), to a different address from which the next instruction will be fetched.

• Hard disk drives are cheaper per gigabyte than solid state drives.
• Hard disks have a longer lifespan than solid state drives

Disadvantages of Hard Disk Drives

• Consumes more power than SDD
• They are noisy.
• They are slower than solid state drives.
• They are susceptible to wear and tear as they have movable parts.

Advantages of Solid State Drives

• Are faster than HDDs
• It is more durable as it does not have moving parts
• Consumes less power
• Are not noisy

Disadvantages of SDD

• It costs more than a conventional hard disk
• Have fewer write/erase cycles compared to a hard disk drive
• Lost data cannot not be recovered

• Only the changes need to be backed up
• The software/OS/settings are unlikely to have changed between backups
• Small number of files likely to be used/edited between backups
• Take less time to backup
• Each backup will take less memory space to store

Full:

• Backup all the data/files and software
• It might not take a significant time to back up entire system
• He might only have a small number of files to be backed up each time
• Safer as have more past versions to revert to
• User may have changed settings on computer
• Faster to restore the backup
• Needs to do a full before he can do an incremental

• Stores the address/location where data will be read/written/accessed/fetched
• stores address/location of data/instruction being processed
• stores address/location of data/instruction next to be processed

MDR or  memory data register

• Stores the data/instruction that is fetched/read from memory
• stores the data that is to be written to memory
• stores the data/instruction from the address in the MAR
• stores data/instruction next to be processed

 Program counter

• Stores the address/location of the next instruction to be run
• stores the address/location of the current instruction being run

Accumulator

• Stores the result of manipulation/process/calculation

RAM stores currently executing programs and data

Instructions

Parallel data transmission

• 8 bits/1 byte/multiple bits sent at a time  
• using many/multiple/8 wires/lines

Serial data transmission

• one bit sent at a time over a single wire

• -more accurate/fewer errors over a longer distance
• -less expensive wiring  
• less chance of data being skewed/out of synchronization/order

• sending data from a computer to a printer
•  internal data transfer (buses)

Serial

• connect a computer to a modem