Revision for IS

Revision for IS

1. Algorithms

   • An algorithm is a set of instructions that describes how to solve a problem
   • Algorithms can be designed using pseudo-code and/or flowcharts. They are written using statements and expressions.

2. Pseudo code

   • Pseudo-code is a simple way of describing a set of instructions in a manner that resembles a programming language. In an algorithm, most processes fall into three main categories: inputs
     • inputs
     • Outputs
     • Processes

3. Protocols

   • Protocols are a set of rules for how computers should communicate across a network
   • Protocols are a set of rules for how data is sent and received on a network.

4. Binary Units

   • Bit
   • Byte
   • Kilobyte
   • Gigabyte
   • Megabyte
   • Terabyte
     • 2 steps higher than MB's
   • Nibble
   • 1000mb in 1 gb
   • 1000 gb in 1tb

5. RAM

   • RAM is quicker to access data compared to virtual memory.
   • Virtual memory is slower to access data compared to RAM.
     • Because the data has to go back to the RAM first
     • Moving data between RAM and virtual memory takes processor time.

6. Virtual memory

   • Virtual memory is used when RAM is full.
   • Part of the secondary storage is used as virtual memory (temporary RAM).
   • Data from RAM is moved to the secondary storage to make space in the RAM for new data.
   • When data in virtual memory is needed, it is moved back to the RAM.

7. Registers

   • Program Counter
     • Stores the address of the next instruction to be run.
   • Memory Address Register (MAR)
     • Stores the address where the data will be fetched/written.
   • Memory Data Register (MDR)
     • Stores the data or instruction which is being fetched/written from memory.
   • Accumulator
     • Stores the intermediate results of a calculation.
   • Not registers
     • ALU
     • Control Unit
     • Cache

8. Client server network

   • examples
     • The school network
     • Playstation Network
     • Any website which you login to
     • Large companies with many computers
   • Better than a peer to peer netwrok beavsue
     • Keep track of files as they will be stored centrally on the server
     • Perform backup as only the files on the server will need backing up
     • install and update software as the server will install these across every device / do not have to do individually
     • Manage network security / user access levels / anti malware software Making sure that only authorised users can use the network
   • All devices are managed/controlled by a server
   • Can install software across the network
   • Share printers with certain computers
   • Control the access of computers to the Internet.

9. Peer to peer network

   • All PCs have equal status (meaning there is no server managing or controlling the network)
   • They share resources with each other (they are all over the network and not in one central point