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algorithms, compilers, bidmas, errors, it has most of what you need to revise for your test
naomi umoru
Flashcards by naomi umoru, updated more than 1 year ago
naomi umoru
Created by naomi umoru about 8 years ago
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high level languages high level languages are easy for the user to understand, and they contain English words. examples of high level languages include Java, python, C++ and ruby.
low level languages low level languages are the computers own language, they include binary zeroes and ones. examples include C, machine code and assembly language.
Trace tables A trace table, also called a trace matrix, can be used to record the outcomes of the test. The trace table for a very simple example, such as x=y+2, would look like this: y x 13 15 25 27 1200 1202
tests valid - the most obvious or common data that should work valid extreme - unusual, extreme or unexpected data, eg the highest and lowest (data that tests the limits but that should work) invalid - data that should definitely fail invalid extreme - data that is at the edge of failure and is nearly acceptable
erroneous data that is the wrong data type
Syntax errors This is an error in the spelling or grammar used when coding. Missing a letter, character or forgetting to include inverted commas/speech marks are common examples of syntax errors. A syntax error will be identified by the translation software as it will be unable to convert the source code into machine code.
execution error An execution error occurs when a program is asked to do something that it cannot, resulting in a ‘crash’. The widely used example of a run time error is asking a program to divide by 0. The code contains no syntax or logic errors but when it runs it can't perform the task that it has been programmed to carry out. Another example is where an attempt is made to access an item in an array which does not exist eg item 11 in an array size 10.
logical error An error in the logic of the code such as using ˂ instead of ˃ or AND instead of OR. The program will execute the code but will produce unexpected results. Logic errors are usually resolved by carrying out a dry run, using a trace table or setting breakpoints to help identify the section of code that contains the logic error.
algorithm decomposition advantages different people can work on different sub-problems disadvantages the solutions to the sub-problem tasks might not combine to solve the original problems. poorly understood problems are hard to decompose.
BIDMAS B- brackets I- indices D- division M- multiplication A- addition S- subtraction
unambiguous not open to more than one interpretation
interpreter using an interpreter, each line of source code will be translated to machine code one line at a time. The advantage of using an interpreter is that the execution will stop immediately if the interpreter translates a line of source code that results in an error. This makes an interpreter a useful tool to assist programmers as they attempt to identify and rectify errors. The interpreter cannot determine the actual error but can indicate the line that was not translated into executable machine code.
compiler A compiler will translate the source code into what is known as object code. The compiler is held in RAM only for the time that it takes to translate the source code into object code. Once object code has been created it is possible to run this code independently of the development environment and translator software. Using a compiler once to create object code makes run time more efficient but if the source code contains errors the programmer would need to re-compile to make use of the corrected object code.
input, process, output A computer receives an input, processes the information, then performs an output. For example, sending a text message from a mobile phone: input - type in the message and press send process - the phone's hardware and network process the message output - the message goes to the receiver
pseudo-code You can write algorithms in plain English before you decide which programming language you want to use. Writing algorithms this way is called pseudo-code.
Runtime errors Runtime errors are errors which will cause the program or computer to crash even if there appears to be nothing wrong with the program code. Running out of memory will often cause a runtime error. This could be because instructions have been written in the wrong order.
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