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Flashcards by hannah ruskin, updated more than 1 year ago
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Created by hannah ruskin
over 8 years ago
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| Question | Answer |
| Give one reason why programmers often use hexadecimal, instead of binary, to represent numbers. | Hexadecimal is easier (for humans) to read (than binary) Hexadecimal is easier to convert (to binary) than denary Numbers are displayed in a more compact way (in hexadecimal than in binary) |
| The ASCII character set uses seven bits to encode every character. What is the total number of characters that can be encoded in ASCII? | 128 (characters) |
| Describe how a black and white image could be represented as a bitmap in binary. | The image is represented as a sequence of pixels. Each pixel/dot is represented by one bit: White is represented by a 0 Black is represented by a 1 White and black are represented using different bit patterns. The same bit pattern used for black and white Metadata about the image is also stored |
| Explain what is meant by the term volatile memory. | Memory content is lost when power is turned off |
| What is normally stored in the non-volatile part of a computer’s main memory? | The computers bootstrapping instructions |
| Explain why having cache memory can improve the performance of the Central Processing Unit | Frequently used data/instructions are stored in the cache meaning they don’t have to be fetched from main memory; Data/instructions stored in the cache memory can be accessed faster than data/instructions stored in the main memory |
| State two characteristics, other than the size of cache memory, that can improve the performance of CPUs | the number of cores/processors; the processing speed/clock speed/number of cycles (per second) of the processor; the bus width; the word size; |
| What is a computer network? | Two or more computers that have been connected together or that can communicate with/send messages to one another |
| State three other built-in physical devices that allow data to be input to a typical tablet computer. | Microphone Camera/Video camera GPS device Motion sensor |
| State and explain two differences, other than cost and storage capacity, that make solid state media a better choice than magnetic media for tablet computers. | Difference: No mechanical parts in solid state media Explanation: Magnetic media are often unsuitable for mobile use because the mechanical parts cannot function during movement Difference: Speed of read access higher in solid state drives. Explanation: Data can often be read more quickly from solid state media than magnetic media. |
| Explain how data is read from optical media such as a CD. | 1. The tracking mechanism moves the laser into the correct position over the CD 2. The CD is spun to ensure all data can be read 3. The CD spins slower when the laser/read-head is above the outer tracks 4. The laser is shone on to the disk 5. The laser is reflected 6. Bumps/pits are raised parts of the disk 7. Bumps/pits form a spiral from the centre to the outside of the disk 8. An opto-electric sensor detects changes in reflectivity; Bumps/pits and lands represent the two possible bit values |
| There are many tools that can help the programmer to reduce errors in their code when developing a computer program. State three tools that can help to identify errors or reduce the chance of there being errors when developing a program. | Watch/Variable table; Breakpoint; Step through; Use of an Integrated Development Environment/IDE; |
| The programmer uses unit testing as part of the development process. Compare unit testing with another type of testing that the programmer could use. In your answer you should also include a description of what unit testing is. | Unit tests or modular tests are performed by the programmer as they are developing the program. They test the correctness of small blocks of code in isolation. Integration testing is performed when all of the different parts of code, such as functions or modules, are complete. This tests whether the units of code work together correctly. System testing takes place after the code has been individually tested and is done without having to have any knowledge of the code itself (black box testing). This tests that the entire system functions correctly. |
| Discuss three advantages and/or disadvantages of using external code sources in a program. | Advantages: The programmer may not have the expertise to develop that particular piece of code themselves It could speed up the development of their own projects by reducing the amount of developing and testing that developers would have to complete. The libraries could be updated by an external body thereby increasing the efficiency of the developers’ own code. Disadvantages: Relying on the correctness of someone else’s program takes control away from the developer. You may need to become familiar with how to use the external code source. The external code source may not be well documented. The external code source may cost money to use. There is a risk of shoe-horning the project if the external code sources do not do exactly what the developer would like them to. |
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