corrections: exam qs

• file size= bit rate(Hz) x length of sound (s) x sample size (BYTES)
• bits to bytes= divide by 8
• bit rate= sampling rate x sampling resolution
• the purpose of a buffer in a computer system is so act as a temporary storage to store data right before it is used by the receiving device, typically in the RAM. example: video buffer when streaming videos
• the feature that describes the relationship between data and its structure is logical schema
• the purpose of a query in a DBMS: allows the user to enter criteria, searches for the data that meets the entered criteria and organises the results to be displayed to the user
• the role of the MAR: holds data/instructions which has been read from or is to be written to the address in the MAR
• interrupts are detected after the completion of the execute stage in the F-E cycle
• the system clock synchronises operations by creating timing signals
• the purpose of relative addressing in assembly language program is to allow re-locatable code because all target addresses can be specified by the base address and offset
• instruction groups in assembly language: input and output of data, arithmetic operations, compare instructions, unconditional and conditional instructions
• advantage of satellites: not fixed in a single location and allows access in remote areas
• disadvantages of satellites: high latency, more expensive than wired methods, signal is affected by bad weather, the transmission speed is slower than fixed line broadband, direct line of sight needed
• benefits of dividing a network into subnetworks: improves security, reduces congestion, allows extension of the network, aids day-to-day management, improves performance
• how a programmer benefits from using commercial licensing: enables the program to be copyrighted, prevents illegal changes to the program, a fee can be charged for the program
• why some programs are distributed under open source license: to allow users to customize the code, allow errors to be reported, allow for collaboration and allow additional features to be added to the code
• characteristics of an embedded system: a combination of hardware and software designed for a specific function, must have a processor, memory and i/o, system is not easily changed by the user
• the role of the DNS

  1. Browser parses the URL to obtain the Domain Name

  2. Browser software passes the domain name to the nearest domain name server

  3. DNS stores a list of Domain Names and matching IP addresses

  4. DNS Name Resolver looks for the domain name in its database

  5. If found, the corresponding IP address is returned to the originator

  6. If not found, the request is forwarded to another high level DNS

  7. The original DNS adds the returned IP address to its cache

  8. The original DNS returns the IP address to the originator

  9. Browser uses the IP address to request the required web page from the web server

  10. Web server retrieves the page and delivers it to the originator

  11. Browser software interprets the script and displays the web page
• difference between vector graphics and bitmaps:
• bitmap is made up of pixels and vector graphics store a set of instructions about how to draw the shape
• bitmap files are usually bigger than vector graphic files hence take up more memory space
• enlarging bitmap can mean the image is pixelated while vector graphics can be enlarged without the image becoming pixelated
• bitmaps can be compressed with significant reduction in size while vector graphic images do not compress well
• bitmaps are suitable for photographs/ scanned images while vector graphics are suitable for geometric shapes
• bitmap graphics use less processing power than vector graphics
• bitmap headers store: confirmation that the file is a BMP, file size, location of image data within the file, color depth, type of compression used (if any)
• pixel density: number of pixels per unit measurement
• how RLE compresses an image: looks for runs of consecutive pixels of the same color, stores the color value once and the number of times it occurs, lossless method of compression
• URL is a reference address to a resource on the Internet. • The URL is passed to the nearest Domain Name Server (by browser software). • DNS server stores a database / list of URLs and matching IP addresses. • DNS (Name Resolver) looks for the URL in its database. • Finds the matching IP address and returns it to the originator. • Or if it cannot find it, it forwards to another Domain Name Server at a higher level. • (Original) DNS server adds the returned IP address to its cache.
• The file is made available from a web/email/FTP server Max 2 1 • The user’s browser is the client software • The client (software browser) requests the file from the server • The desired file is returned to the client computer
• The purpose of Ann IP address:Gives each device on a network an identifier //2 • Each address is unique within the network • Allows a device/gateway/node to send data to the correct destination /
• A bridge: Has the same functions as a router except connects two dissimilar networks // networks that use different protocols