Computing Revision

Computing Revision

1. Algorithms and promming

   • Variables can change when the program is running, however constants cannot change. Constants can only be changed in the actual code.
   • sequence = A list of instructions.
   • selection = Decisions (IF, ELSE IF, ELSE).
   • iteration = Repeating code.
   • CRIBS
     • Character - A single character.
     • Real - Decimal numbers.
     • Integer - Whole numbers
     • Boolean - True/False
     • String - Any characters
   • SQL
     • This is a programming language used to manage and search databases. It is used a lot in web databases.

2. Binary

   • Bit, nibble, byte, kilobyte, megabyte, gigabyte, terabyte and petabyte.
   • Overflow errors can occur when you add 2 8 bit binary values together and the answer becomes 9 bits.
   • Hexadecimal is much easier to remember and write because each hexadecimal value is equivalent to 4 bits of binary. This also reduces the risk of errors.

3. System security

   • Threats posed to networks
     • data interception and theft
     • denial of service attacks
     • poor network policy
     • social engineering seeing people as the ‘weak point’ in secure systems
     • phishing
     • brute force attacks
     • malware
   • Ways to prevent particular threats to networks
     • penetration testing
     • anti-malware software
     • user access levels
     • passwords
     • firewall
     • network policies
     • encryption

4. software

   • proprietary software
     • is owned by an individual or a company usually the one that developed it there are almost always major restrictions on its use, and its source code is almost always kept secret
   • open source software
     • The term "open source" refers to something people can modify and share because its design is publicly accessible.
   • custom written software
     • software system which is developed specifically for a company or business.
   • off the shelf software
     • Short for commercial off-the-shelf, an adjective that describes software or hardware products that are ready-made and available for sale to the general public. For example, Microsoft Office

5. Wire and wireless networks

   • Networks allow you to communicate with other devices and share resources.
   • You can store all your files in one central location for all of the devices to access.

6. Translators and facilities of languages

   • Assembler Translates assembly language into low level code
   • Compiler Translates the source code into machine code all at once. It is used to make executable files which can be distributed.
   • Interpreter Translates the source code into machine code 1 line at a time. It is normally used to test programs in a run time environment. Therefore it is useful for debugging
   • High level language
     • Is portable on different machines
     • Python, Scratch and Javascript are all examples
     • One high level instruction is represents many low level instructions
     • Understood by humans
   • low-level language
     • Designed to be understood by the CPU
     • Only works on the CPU it is been designed for
     • Assembly language and machine code (binary) are both examples
   • run time environment
     • Allows you to run your code quickly. This is good when you are testing during the development of your program
   • Editor
     • Allows you to write and modify code. Has features such as auto-colour coding and auto indentation
   • Translator
     • I know the characteristics of high and low-level languages
   • Error diagnostics
     • Allows you to find and debug errors in your code. It will identify the line where the error is and may even suggest ways to fix it.