Computer Science AS CIE
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data-representation as5 主题
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multimedia as3 主题
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compression as2 主题
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networks-and-the-internet as11 主题
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computers-and-components as5 主题
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logic-gates-and-logic-circuits as2 主题
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central-processing-unit-cpu-architecture as6 主题
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assembly-language- as4 主题
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bit-manipulation as1 主题
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operating-systems as3 主题
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language-translators as2 主题
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data-security as3 主题
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data-integrity as1 主题
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ethics-and-ownership as3 主题
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database-concepts as3 主题
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database-management-systems-dbms- as1 主题
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data-definition-language-ddl-and-data-manipulation-language-dml as1 主题
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computational-thinking-skills as1 主题
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algorithms as4 主题
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data-types-and-records as2 主题
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arrays as2 主题
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files as1 主题
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introduction-to-abstract-data-types-adt as1 主题
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programming-basics as1 主题
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constructs as2 主题
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structured-programming as1 主题
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program-development-life-cycle as1 主题
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program-design- as2 主题
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program-testing-and-maintenance as3 主题
program-libraries as
Exam code:9618
Program libraries
What is a program library?
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A program library is a collection of pre-written code (called library routines) that programmers can reuse in their own software
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These routines can perform common tasks such as:
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Sorting
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Displaying graphics
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Playing sounds
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Managing data
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Advantages of using program libraries includes:
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Advantage |
Explanation |
|---|---|
|
Saves development time |
Pre-written routines can be reused, so programmers don’t need to write common functions from scratch |
|
Promotes code reuse |
Well-tested routines can be used in multiple programs, reducing duplication |
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Improves reliability |
Library routines are usually thoroughly tested and debugged, reducing the chance of errors |
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Easier maintenance |
Updates to a library routine automatically benefit all programs that use it (especially with DLLs) |
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Efficient memory usage |
Dynamic link libraries (DLLs) are only loaded when needed at runtime, saving system resources |
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Standardisation |
Promotes consistency in how common tasks (e.g. file handling, sorting) are implemented |
What is a DLL?
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A Dynamic Link Library (DLL) is a file that contains pre-written code, such as functions or routines, that can be used by multiple programs at runtime
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Aspect |
Advantages |
Disadvantages |
|---|---|---|
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Program Size |
Reduces program size by keeping reusable code separate |
– |
|
Memory Usage |
Saves memory by sharing DLLs between programs |
– |
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Code Reuse |
Encourages reuse of common routines (e.g. sorting, sound) |
– |
|
Modularity |
Supports modular design for easier development and maintenance |
– |
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Ease of Updates |
Update a DLL once to improve all programs that use it |
Can cause version conflicts if newer DLLs aren’t compatible |
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Dependencies |
External DLLs can be reused by many applications |
Program may fail to run if a required DLL is missing |
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Security |
– |
Malicious or altered DLLs can pose security risks |
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Debugging |
– |
Errors in DLLs can be hard to trace across multiple programs |
Worked Example
Jennifer is writing a computer program for her A Level homework.
Jennifer uses a program library to help her write her computer program.
Describe how a program library can be used while writing a computer program. [2]
Answer
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Program libraries store pre-written functions and routines [1 mark]
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The program library can be referenced/imported [1 mark]
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The functions/routines can be called in her own program [1 mark]
Responses