Computer science

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  • Created by: jp3louis
  • Created on: 31-05-16 18:21
State the denary representation of the binary number 10010111
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State the hexadecimal representation of denary number 125.
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Give 3 reasons why programmers use hexadecimal rather than binary?
easier for humans to read, numbers are displayed in a more compact way, quicker to type, more accurate, less mistakes
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What is the total number of characters that can be encoded in ASCII?
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Whats the correct order for converting sound into a digital form>
Microphon picks up sound waves, it is converted into an electrical analogue signal, the value is read and rounded and then the binary representation is stored.
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Describe how a black and white image could be stored as a bitmap in binary?
White = 0 black = 1. Each pixel and dot are represented as one bit. The image is represented as a series of pixels.q
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What is volatile memory?
Memory content is lost when power is turned off.
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What is stored in the non-volatile part of the memory?
The computers instructions and operating systems.
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Why would have a cache memory improve the peformance of the CPU?
Frequently used data is stored in the catch so it doesn't need to be fetched from the main memory this means it can be accessed quicker.
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Give 3 things that can improve the performance of CPU's
Number of cores or processors, type of cache memory and the speed.
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How many parameters does the function FindHighest have? (refer to picture 1 off the 2014 paper)
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The function uses iteration. What number does it start on?
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This function also uses selection. What number does it start on?
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It also uses the variable assignment. Give the line number where it is first used.
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The variable i only has scope between lines 3 and 7. Explain with reference to variable i what scope means.
Variable i is not defined outside those lines.
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What is a computer network?
A computer network is where two or more computers are connected that can communicate with eachother,
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Would displaying a HTML page occur at the client, server end or both?
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Would receiving messages happen at the client, server end or both?
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Would starting the handshaking process happen at the client, server end or both?
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State 4 built in physical devices that allow data to be input into a typical computer?
Touch screen, gps, microphone, camera,motion snesor.
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State 2 differences that makes solid state media better than magnetic media.
Solid state is silent, Less heat generated, more compact, no mechanical parts in solid state.
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Explain how data is read from optical media such as a cd
A cd is spun and a laser is shone onto the disc. The laser is reflected and any bumps form a spiral from the centre to the outside of the disc. The bumps represent two possible bit values
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What is a row of data within a table called?
A record.
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What is it called when something uniquely identifies a row of data
Primary key.
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What is it called when things are linked between tables?
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What is used to speed up searches?
An index.
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Name 4 ways we can identify errors in programs.
Syntax colouring, automated testing, breakpoint, variable tables and code completion.
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Give different types of testing and what they do.
Unit tests - performed by the programmer as they are making the program. They test the correctness of small blocks of code. Integration- done when all functions and moduels are complete and this tests if they all work together.
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Give some advantages of using external code sources in a program.
They might not know how to do it so by getting it elsewhere, they can do it. Speed up the development of programs and finally libraries could be updated so it is more efficent.
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Give some disadvantages of using external code.
Relying on someone else, have to learn how to use the external code, may cost, security risks.
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What is a dedicated computer?
A computer that has been designed for a specific purpose.
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What is a general purpose computer?
Don't have one main function.
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Give the some inputs.
Keyboard, mouse, cashless reader, keypad, microphone
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Give some outputs.
Printer, monitor or screen, projector and speakers, gps.
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Give the input, process and output of a cash machine.
Input: user puts in their pin. Process: System checks to see if it was valid. Output: Option on screen such as cash release.
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Once software engineers are happy with their code, what happens next in testing?
It is sent to beta testers who can see if any errors were over looked.
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In the context of computing, what does redundancy mean?
Spare, excess or additional - so if a computer has redundant storage, it means it is has over two hard drives.
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Why do we use redundancy in computing?
So if something fails, we have something to fall back on. Like social media uses two hard drives so if one stops working, the other one will still work.
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What is 8 bits?
1 byte.
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What is a disaster recovery plan?
A plan of what to do if the computer system goes down.
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What are proprietary standards?
They are owned and controlled by companies like Microsoft ( .docx)
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What are industry standards?
Common agreed standards in industry like UBS to connect devices to computers.`
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What are de jure standards?
HTML - the only way to write and read webpages.
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What are open standards?
Publicly available so everyone can benefit from the code and updates.
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Give the name of 3 laws.
Data protection act, computer misue act, copyright and patents act.
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What is the waterfall model?
It is a system lifecycle which does each step at a time and each step has an output. It can go back on itself but this means all the steps it has gone through needs to be redone.
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What is the spiral model?
A system lifecycle which develops the software in repeating stages. After each run a prototype is made and this is used for larger projects
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Give the advantages of using the waterfall model.
Easy to managed as it is one step at a time, defined processes and outputs.
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Give the disadvantages of using the waterfall model.
If you want to go back, you have to redo steps that have already been completed. Can be costly and timely.
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Give some advantages of the spiral model.
Well defined steps, highlights issues quickly due to prototypes.
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Give some disadvantages of the spiral model.
Takes time to build prototypes so it takes longer for the customer to see the product. Longer to make so costs more.
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What is a database?
A persistent store of related data that is organised so it is useful.
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What is a field?
A column in a database that holds data.
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What is the foreign key?
The context of relational databases. It is a field in one table that links to other tables.
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What is an index?
Used in a database to speed up searches.
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What is the primary key?
Uniquely identifies a row of data
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what is a record?
A row of data within a table.
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What is structural testing?
You write the tests bases on the code. It should have test coverage which means every line should be run during testing.
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What is functional testing?
Testing against the users needs. You don't look at the code while writing test cases and instead you look at what it should do.
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What are unit and modular tests?
Performed by the programmer as they make the code. They test small blocks of code one bit at a time.
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What is system testing?
Takes place after the code has been individually tested and is done without any knowledge of the code itself (also called black box testing).
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What are some advantages of ring networks?
Very fast and all data occurs in the same direction so there are no data collisions.
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What are some disadvantages of ring networks?
If a single machine is switched off, then the network does not work. If a cable it breaks then it also doesnt work.
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What is a network?
When two or more computers are joined together in order to exchange information.
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What is it called when a computer is not in a computer network?
Stand alone computers.
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Give an advantage of star networks.
Reliable as if one connection fails it does not affect the others. Good performance as fewer data collisions happen as they all have their own line. Good security as they all have to go through the server before interacting.
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Give a disadvantage of star networks.
Expensive to instal - alot of cables needed. Extra hardware needed like hubs, switches and wiring centres. Installing it needs a professional.
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Give an advantage of a bus network.
Cheap and easy to instal.
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Give a disadvantage of a bus network.
If there's a problem with the cable, they all stop working. Many workstations can lead it to run slowly.
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Give some advantages of networks (general)
Backup is easier, communications, security
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Give some disadvantages of networks (general)
Costs, staffing, viruses, file access as anyone can get to them.
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Using 2 bits per pxiel, we get how many colours in a picture?
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Using 3 bits per pixel, we get how many colours?
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What is resolution measured in?
Pixels per inch. (dpi) The more pixels per inch, the higher the resolution of the picture.
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A higher sample rate - give an advantage and disadvanatge.
ADV: Produces better quality sound. DIS: Takes more space.
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Sound waves are what?
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Why is it bad that sound waves are analogue and not digital?
Analogue waves change alot and do not have a specific measurable value however a computer needs to have specific measurable values to work. This means it must be changed to digital.
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What does ROM do?
Read only memory stores the boot sequence and this checks that all of the hardware is present and connected.
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ROM is volitile or non volitile?
Non volitile so data is stored when it is turned off.
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A single processor can run how many instructions at one time?
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Why do we uses quads or duals?
Runs more processes at one time.
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Is RAM volitile or non volitile?
Volitile so it will not saved when it is shut down.
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Give some examples of utilities.
Anti virus software, firewall, disk management and backup software are examples.
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What is GUI?
Graphical user interface and this is used to manipulate windows, click on buttons and scroll through menus.
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What does an OS do?
An operating system controls the systems hardware.
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What is an open source?
A source that is available and shared by programmers. It is not owned by anyone.
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What are proprietary?
A program that is developed commercially to make money. It is sold with a license.
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How many numbers are in denary?
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What is hexadecimal?
A mixture of letters and numbers. 0-9.
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What is the definition of data?
Consists of facts and statistics out of context and these are processed by a computer.
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What is the definition of information?
A sentence or sequence in which it has been put into context and this gives the data meaning.
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What is a variable?
Data entities whose values CAN be changed.
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What is a constant?
A data entities whose vales CANNOT be changed.
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What is an integer?
A whole number (it is a data type)
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What is a float?
A number that is not whole (it is a data type)
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What is a real?
Numeric data in decimal form. It is used when we need more accurate data
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What is a string?
A set of characters put together
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What is the primitive data type of a boolean?
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What is a boolean?
It represents the values of true and false. You can have AND, OR, NOT.
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What is the operator?
Less than.
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What is the operator?
Less than or equal to
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What is the operator? ==
Equal to.
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What is the operator? !=
Not equal to.
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What is the operator? >=
Greater than or equal to.
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What is the operator? >
Greater than.
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What are arrays and linked lists used for?
Both designed to store multiple elements, most often of the same type.
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What is an array?
An ordered arrangement of data elements that are accessed by their referencing their location within the array.
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What is a one dimensional array?
Is a structured collection of components that can be accessed individually by putting in things to get a single element out of the array with an index value.
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What is a two dimensional array?
Where there are arrays all over like one array will be in one row and another array will be in the next.
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What is the study of data structures?
Organising data so it is suitable for computer processing.
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Why would a programmer want to use integers rather than a real?
Real takes up more storage, calculations take longer as it is decimals also mistakes could happen more.
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Write the following sentence as a boolean: when the door is open and it is cold outside I have to wear my coat.
If (''door is open'') AND (''it's cold outside'') then wear 'coat'.
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The primary purpose of software is to turn data into what?
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Explain the term concurrent
When something is happen at the same time as something else.
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Explain, using an example, what the term one dimensional array is.
A one dimensional array is a list of variables. To create an array you need to define an array variable of the desired type. A python example could be: carMakers = [''ford'', ''Land rover'', ''vauxhall''
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What is iteration?
where a statement is executed in a loop until the program reaches a certain state. An example of this could be while statements as they keep going until it is gone.
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What is a procedure?
A block of code that performs a task without returning a value.
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What is a function?
A block of code that performs a task and returns a value.
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What are the two types of function and what do they do?
User - defined and this is created by the user for their program. Built in functions are part of the programming language.
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What are built in functions also called?
Library functions
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Why is it good to have built in functions?
They are always avaliable for the program and they save a lot of effort in writting code as this saves time.
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What is a parameter?
A special sort of variable that is used in a subroutine to refer one of the pieces of data provided as an input to the subroutine. Thjis allows the passing of values to the procedure or function for use inside of it.
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What is the purpose of using procedures and functions in programming languages?
They allow the repetition of certain sections of the code. They also allow themselves to be called at any point.
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What is the main difference between a procedure and a function?
A function carries out actions and returns a value where as procedures don't return values.
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What is a procedure scope?
when a variable can be read and modified only from within the procedure in which it is declared.
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What is a module scope?
When a variable is declared before and outside of any procedure within a regular program module.
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What is a project scope?
It is declared when someone uses a public command keyword. Variables in a project scope can be read and modified from any procedure contained within any module within the program or project.
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What is a global scope?
Where variables have the capability of being accessed from anywhere within the project that contains their declaration as well as from other projects that refer to the initial point.
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What are the three types of errors?
Syntax, run-time and logic.
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Describe what a syntax error is.
They occur when the programmer fails to obey one of the grammar rules. This might be wrong punctuation or a misspelled word.
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Describe what a run-time error is
They occur when the program instructs the computer to carry out an operation that is either not designed to do or slow to do.
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Describe what a logic error is.
These errors are hard to find as there is no obvious indication of where it is. The program runs well but not in the way the programmer intends it to do so. The most common reasons for this happening is that the programmer was careless.
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What is dry run testing?
It is carried out on the algorithm which is written in pseudo code or flowchart. This testing is done prior to the code being made. An advantage of this is that it spots problems before development stage.
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The process of testing a program for errors during its execution is a cyclic activity called what?
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What two things are needed to debug code effectively?
The ability to test each of the instructions provided by a program. The capability to retrieve the information about the results on instructions, changes in the program, error conditions and what it was doing when it found a problem.
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Why do we use trace tables?
To test algorithms to see if any logic errors occur while the algorithm is being processed.
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State what happens when programming statements are written in the wrong order and the state the name for this type of error.
Run time error and this happens when the program tells the computer to do something but it goes to slow and crashes it.
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Why do we use SQL?
To communicate with a database.
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State 4 essential parts of a computer system.
Input, output, storage, process.
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Card 2


State the hexadecimal representation of denary number 125.



Card 3


Give 3 reasons why programmers use hexadecimal rather than binary?


Preview of the front of card 3

Card 4


What is the total number of characters that can be encoded in ASCII?


Preview of the front of card 4

Card 5


Whats the correct order for converting sound into a digital form>


Preview of the front of card 5
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