Subprograms: functions and procedures

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Notes de leçon Diapos Questions d'entraînement

Notes de leçon

Why subprograms?

A subprogram is a named block of code that does a specific job. They make programs modular, easier to read, test, reuse and maintain, and support team development.

Calling a reusable subprogram

Procedures and functions

A procedure performs actions but does not return a value to the caller.
A function returns a value: RETURN result.
Example: FUNCTION area(w, h) RETURN w×h ENDFUNCTION. Call: x = area(3, 4) gives 12.

Parameters and arguments

Parameters are variables in the definition (w, h); arguments are values passed when calling (3, 4). Parameters make subprograms flexible.

Definition and call

Scope

Scope describes where a name can be accessed. A local variable or parameter is accessible within its local scope; a global name has wider program scope under this lesson’s model.
Scope is different from lifetime. Prefer local variables and explicit parameters to reduce unintended changes to shared state.

Names and scope

Structured programming

Use sequence, selection and iteration to organise control flow. Divide a complex solution into focused subprograms with clear interfaces.
A main program can call subprograms; those subprograms may call others.

Library routines

A library routine is a prewritten reusable subprogram provided by a library; some are built into the language environment.
Using a tested routine can save implementation time, but check its parameters, return value and assumptions.

Diapos

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Questions d'entraînement

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1.What is a subprogram?
Easy
- Aa named block of code that does a job
- Ba variable
- Ca loop
- Dan input
2.In a function, what does RETURN followed by an expression do?
Easy
- Asends a value back to the caller
- Bends the program
- Ccreates a loop
- Dprints
3.What is a procedure?
Easy
- Aa subprogram that does not return a value
- Ba subprogram that returns a value
- Ca variable
- Da loop
4.What is a parameter?
Easy
- Aa variable in a subprogram definition
- Ba value passed in
- Ca loop
- Da function
5.What is an argument?
Easy
- Aa value passed to a subprogram
- Ba variable in the definition
- Can error
- Da loop
6.Why use subprograms?
Easy
- Ato reuse code and make programs easier to maintain
- Bto slow programs
- Cto add errors
- Dto avoid variables
7.What is a local variable?
Easy
- Aone accessible only within its local scope
- Bone accessible everywhere
- Cone that must be constant
- Done that must control a loop
8.What is a global variable?
Easy
- Aone accessible throughout the program
- Bone inside a subprogram
- Cone that never changes
- Da loop

Plus de questions

9.Which is better practice: local or global?
Easy
- Alocal variables and parameters
- Bglobal only
- Cneither
- Dboth identical
10.What is the result of square(5) for square(n) RETURN n×n?
Easy
- A25
- B10
- C55
- D5
11.Which statement calls area with arguments 3 and 4 and stores its returned value in result?
Easy
- Aresult = area(3, 4)
- Barea(3, 4) only
- CRETURN 3
- DFOR area
12.Which makes code easier to test?
Medium
- Asmall subprograms each doing one task
- Bone huge program
- Cno functions
- Dglobal variables everywhere
13.What is the output? FUNCTION add(a, b) RETURN a + b ENDFUNCTION OUTPUT add(2, add(3, 4))
Medium
- A9
- B5
- C7
- D12
14.In pseudocode that distinguishes functions and procedures by returned values, how should a subprogram returning a result be classified?
Medium
- Ait should be a function
- Bit works as a procedure
- Cerror always
- Dnothing
15.What is a library routine?
Medium
- Aa prewritten subprogram provided by a library
- Ba variable created by the user
- Ca repetition statement
- Da flowchart shape
16.What is 'structured programming'?
Medium
- Ausing sequence, selection and iteration to organise control flow
- Busing no loops
- Cusing only variables
- Davoiding every subprogram
17.Why can global variables cause problems?
Medium
- Aany part of the program can change them
- Bthey are too fast
- Cthey use no memory
- Dthey cannot store numbers
18.In FUNCTION f(x) RETURN x×2 ENDFUNCTION, what is x called?
Medium
- Aa parameter
- Ban argument
- Ca constant
- Da loop
19.In the call f(5), what is 5 called?
Medium
- Aan argument
- Ba parameter
- Ca constant
- Da procedure
20.Why might a team use subprograms?
Medium
- Adifferent people can write and test different parts
- Bto hide code
- Cto avoid planning
- Dto slow work
21.Which problem does modularity help solve?
Medium
- Acomplexity in large programs
- Bhardware faults
- Cslow internet
- Dpower cuts
22.What is 'reuse'?
Easy
- Ausing the same code in many places
- Bdeleting code
- Ccopying errors
- Dignoring code
23.What is a 'call'?
Easy
- Arunning a subprogram
- Bdefining a subprogram
- Cending it
- Ddeleting it
24.What does a procedure typically do?
Medium
- Aoutputs a message or changes data
- Breturns a number
- Csorts nothing
- Dstores constants
25.What is a 'main program'?
Medium
- Athe part that calls subprograms
- Ba subprogram only
- Ca variable
- Da data type
26.A function returns a value.
Easy
True or false?
27.Subprograms make code easier to reuse.
Easy
True or false?
28.A procedure always returns a value.
Easy
True or false?
29.A local variable is accessible only within its declared local scope.
Easy
True or false?
30.Global variables are the safest choice.
Medium
True or false?
31.Which are benefits of subprograms?
Medium
- Areuse
- Beasier testing
- Ceasier maintenance
- Dteamwork
- Elonger code
32.Which appear explicitly in the call area(3, 4)?
Medium
- Athe subprogram name area
- Bthe argument 3
- Cthe argument 4
- Dthe formal parameter name width
- Ethe returned area value
33.Explain the difference between a function and a procedure.
Medium

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