Computer-science_A-level_Cie
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computers-and-components6 主题
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logic-gates-and-logic-circuits2 主题
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central-processing-unit-cpu-architecture6 主题
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assembly-language-4 主题
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bit-manipulation1 主题
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operating-systems3 主题
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language-translators2 主题
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data-security3 主题
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data-integrity1 主题
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ethics-and-ownership3 主题
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database-concepts3 主题
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database-management-systems-dbms-1 主题
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data-definition-language-ddl-and-data-manipulation-language-dml1 主题
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computational-thinking-skills1 主题
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algorithms14 主题
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data-types-and-records2 主题
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arrays2 主题
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files1 主题
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introduction-to-abstract-data-types-adt1 主题
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programming-basics1 主题
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constructs2 主题
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structured-programming1 主题
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program-development-life-cycle2 主题
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program-design-2 主题
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program-testing-and-maintenance3 主题
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user-defined-data-types1 主题
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file-organisation-and-access-3 主题
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floating-point-numbers-representation-and-manipulation3 主题
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protocols2 主题
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circuit-switching-packet-switching1 主题
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processors-parallel-processing-and-virtual-machines5 主题
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boolean-algebra-and-logic-circuits4 主题
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purposes-of-an-operating-system-os3 主题
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translation-software3 主题
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encryption-encryption-protocols-and-digital-certificates3 主题
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artificial-intelligence-ai4 主题
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recursion1 主题
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programming-paradigms4 主题
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object-oriented-programming7 主题
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file-processing-and-exception-handling2 主题
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data-representation5 主题
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multimedia3 主题
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compression2 主题
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networks-and-the-internet11 主题
program-libraries
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:
|
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 |
|
Improves reliability |
Library routines are usually thoroughly tested and debugged, reducing the chance of errors |
|
Easier maintenance |
Updates to a library routine automatically benefit all programs that use it (especially with DLLs) |
|
Efficient memory usage |
Dynamic link libraries (DLLs) are only loaded when needed at runtime, saving system resources |
|
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
|
Aspect |
Advantages |
Disadvantages |
|---|---|---|
|
Program Size |
Reduces program size by keeping reusable code separate |
– |
|
Memory Usage |
Saves memory by sharing DLLs between programs |
– |
|
Code Reuse |
Encourages reuse of common routines (e.g. sorting, sound) |
– |
|
Modularity |
Supports modular design for easier development and maintenance |
– |
|
Ease of Updates |
Update a DLL once to improve all programs that use it |
Can cause version conflicts if newer DLLs aren’t compatible |
|
Dependencies |
External DLLs can be reused by many applications |
Program may fail to run if a required DLL is missing |
|
Security |
– |
Malicious or altered DLLs can pose security risks |
|
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