WJEC A2 Computing Unit 3.6->3.8 Cheat Sheet by Horatio

Voice input involves the computer "­lis­ten­ing­" for spoken words from the user.

1. This technology may be difficult to use due to the complexity of natural language
2. The computer may not understand all ways to phrase a single command.
3. The computer may not be able to understand different accents.
4. Background noise may render the user's voice uninte­lli­gible.

Opcode refers to the operative component of the machine code instru­ction. This might be ADD, where the data in this case would be the number to add(and would come after the opcode).

Assembly code is one-to-one with the mnemonic codes, but due to the existence of variables and labels transl­ation becomes more difficult.
1. Labels are converted to memory addresses and stored in a symbol table(not the same kind as in lexical analysis, though!).
2. After that, mnemonics are converted into their binary counte­rparts and are combined with binary repres­ent­ations of data.

The IDE may automa­tically highlight key words like "­if" or "­pri­nt", based on the language being used. Also, most IDEs will implement automatic line numbering.

Breakp­oints will make the program halt at a specific line of code.

This allows potent­ially proble­matic or otherwise unwanted changes to be rolled back, or to create stable builds at a specific point in time and still allow develo­pment to continue.

Systems Design Evaluation helps the company and client to determine whetherr the project was a success. This involves consid­ering many criteria:

Whether the program runs effici­ently and effect­ively.

Determine whether the system has cost more or less than expected.

This ensures that previously compiled libraries are loaded into a program at compil­e-time and the required links are created. The code from the libraries then becomes part of the final executable code.

A Translator is any piece of software which converts higher­-level source code into machine code. These are compilers, interp­reters or assemblers.

1. An interp­reters translates source code into machine code line-b­y-line, executing each line as it goes.
2. This means that source code only has to be written once to run on any machine that has an interp­reter for it.
3. It's easier to test single lines of code
4. Since the source code is compiled at run-time, this may slow down the system.
5. It's much easier for other people to view the source code, which may compromise intell­ectual property.

CASE stands for Computer-Aided Software Enginee­ring, and refers to a type of software which helps developers to create systems and programs. It may include any of the following:

Helps the developer to create data flow diagrams or flowcharts.

This might include schedu­ling, task assign­ment, etc.

This helps the developer to quickly create screen designs, menus, etc without having to explicitly program them.

This is also known as haptic feedback, and it refers to vibrations or other sensations that the computer may respond with once the user has performed an action­(i.e, pressing a key on a touchs­creen keyboard)

Systems Design Validation is the process of testing a system to ensure that the designed product meets the requir­ements.

1. This is generally carried out as early in the project as possible.
2. It often involves things like bringing in customers to get feedback on the user interface.
3. Methods such as Agile generally make use of multiple smaller design reviews than a single large one.

Allows the developer to easily create diagrams and flowcharts which represent the flow of data within the program.

Allows multiple developers to easily work on the same program at the same time without causing merge conflicts. This is included in most Lower CASE tools.

Allows bug reports to be filed, assigned and eventually marked as "­sol­ved­".

This involves "­taking over" the user's senses in order to make them feel as though they have entered an altern­ate(or virtual) reality.

1. This is usually done via goggles, contro­llers and earpieces.
2. Each eye piece in the goggles relays a slightly different image to give the impression of a 3D image
3. However, this may cause some users to feel nauseous

Interm­ediate code is code that is compiled but not read directly by the end user's CPU. It's interp­reted by an interm­ediate virtual machine which can then interact with the CPU.

1. This is generally faster than interp­reted languages, since the instru­ctions aren't being rapidly compiled to machine code but rather fed to an abstra­ct/­virtual CPU.
2. The code is cross-­pla­tform, as long as the same VM can be installed on many platforms.

1. Spaces, comments etc are removed.
2. All keywords, constants and identi­fiers are replaced with more space-­eff­icient tokens. This is known as tokeni­zation.
3. A symbol table is generated which holds the addresses of variables and functions.

1. Check for semantic errors, like ensure that all variables have been declared, types are used correc­tly(not multip­lying strings), etc.

1. Optimize the code by limiting the number of jumps it has to do, "­unr­oll­ing­" loops, etc.

Touch screens are screens that take in physical input from capacitive touch.

1. If selectable elements are too small or close together, it may be difficult to select with the average finger.
2. Touch screens are very intuitive, especially for small children.