computer science revision

computer science revision

1. Parts of the CPU

   • The ALU is the part of the CPU that performs simple calculations such as True of False statements
     • ALU
   • The CU stands for the Control Unit. This is a place where instructions are carried out in the Fetch, Decode and Execute Cycle.
   • The Registers:
     • The registers hold tiny bits of data that are needed by the CPU.
   • Accumulator

2. RAM , ROM and Virtual Networks

   • ROM
     • The ROM contains non volatile memory. This is a read only memory and cannot be written to.
     • ROM comes in tiny microchips that are built into the motherboard of the system.
     • The ROM contains all the start-up information a computer needs to work.
   • RAM
     • If a computer has insufficient RAM, the computer may run slowly. This is because of the amount of virtual memory used.
     • The more RAM a computer has, the more applications you can run at any one time.
     • The RAM stores running programs and stores them in the background.
   • Virtual Memory
     • Created when RAM is too slow of poor in performance.

3. Types of storage

   • Optical
     • Cheap
     • Reliable
     • Examples include CD's , and Blu-ray discs.
     • Can hold up to 25GB depending on the type of disc.
     • Less popular today
     • Not in phones
     • Easily sracthed
   • Flash
     • Used by ROM chips
     • Types of flash memory
       • USB pen drives
       • Much slower than SSD's
       • SD's cards
     • Common type of non volatile memory.
   • Magnetic
     • High capacity
     • Very reliable storage
     • Traditional internal storage for PC's
     • A hard disk is made of several metal disks and can spin at lot of revolutions a minute which is called RPM for short.
     • Data is stored in stored in areas called sectors.

4. Network Layers

   • Data link layer: Passes data over the physical data layer.
   • Network layer: passes packets over local and wide area networks
   • application layer: Turns data into weskits and applications. e.g http
   • Transport layers: Controlling the efficient flow of data across the TCP
   • self contained rules called protocols which are used to transport data across networks.
   • SMPT: To send emails

5. Which is the fastest?

   • 1: Fastest : Registers
     • 3:RAM
     • 6:BluRay
     • 7: Slowest : CD
   • 2: Cache
   • 4:SSD
   • 5:HDD

6. Full and Partial mesh topologies

   • Partial mesh topologies connect to most of the computers on a network.
   • A disadvantage is that the caballing
     • Full mesh topologies connect to all computers and contain more than ones route to a computer in case one fails.

7. How URL's get converted into a IP address

   • When we type an address into a server, the domain name is check in the DNS server and matches the IP address to the domain name
   • domain name: A name of a website

8. Over a network, you can share data, share peripheral devices, and this is a benefit. All the computers can access a shared area and if one computer goes down, the user can log on to another computer and the data would still be there.