Computing science

Computing science

1. networks

   • peer to peer
     • cheap to set up
     • hard to implement security
     • hard to back files up
   • client server
     • easy to implement security
     • very expensive to set up
     • easy to back files up

2. file size calculations for pictures

   • number of pixels high x number of pixels long x color depth
     • example
       • you have a picture 600 pixels by 600 pixels and have an 8 bit color depth what is its file size
         • 600 x 600 x 8 to show size in bits
           • 2880000 bits
             • divide by 8 to show bytes
               • 360000 bytes
                 • divide by 1024 to show kilobytes
                   • 351.5625 KB is the file size

3. memory

   • RAM
     • Random Access Memory
       • deleted when the PC is turned off
       • stores files temporarily
       • can be written to
   • ROM
     • Read Only Memory
       • is kept when the PC is turned off
       • cannot be easily written to

4. CPU

   • ALU
     • arithmetic and logic unit
       • does the calculations and logic descisions
   • REGISTER
     • temporarily stores the location to access files
   • CONTROL UNIT
     • tells everything what to do in the computer

5. types of validation

   • presence check
     • checks that a box has been filled with say an email
   • restricted choice
     • you can only put certain information in (countries name)
   • range check
     • checks the entered information is within a set range (Date of birth)
   • type check
     • checks the entered information is the right type (string, numerical, date/time, e.t.c)
   • length check
     • makes sure that the information entered is not longer than a set length and no shorter than a set length (name)
   • validation check
     • checks information entered is correct

6. databases

   • fields
     • they can include
       • I.D
         • field type is text
       • name
         • field type is text
       • date of birth
         • field type is date and time
   • records
     • within records there are files
       • files
         • within files there are fields

7. images

   • bitmap
     • bit mapped images are manipulated at a pixel level
     • the image becomes pixelated when enlarged
     • it is ideal for photos and realistic
   • vector
     • vector images are manipulated at an object level
     • typically the file size is small, it will increase as more objects are added
     • it can be enlarged without affecting quality