Subroutines (procedures And Functions)
Übersicht
Open the skeleton program that Paper 1 is built around and you will not find one long list of instructions. You will find a dozen named blocks: one that creates the board, one that places the snakes and ladders, one that displays the board, one that makes a move. Nothing forced the author to write it that way, and every real program is written that way, which is a strong hint that something is being gained.
This lesson covers what a subroutine is, why programs are built out of them, and the two channels through which data travels between a subroutine and the code that called it. Parameters carry data in; return values carry it back out. You will also meet local and global variables, which is where the specimen paper puts two of its marks, and you will learn to say precisely what happens when a subroutine is called rather than waving at it.
Ziele
- Understand the concept of subroutines.
- Explain the advantages of using subroutines in programs. Use and describe the use of parameters to pass data within programs.
- Use subroutines that return values to the calling routine.
Mindmap
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Unterrichtsbewertung
Herzlichen Glückwunsch zum Abschluss der Lektion über Subroutines (procedures And Functions). Jetzt, da Sie die wichtigsten Konzepte und Ideen erkundet haben,
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- Which statement best describes a subroutine? A. A variable that holds several values B. A named out of line block of code that is executed by writing its name C. A loop that repeats a fixed number of times D. A file that stores program output Answer: B
- How many parameters does the subroutine SUBROUTINE Total(A, B, C) have? A. 0 B. 1 C. 3 D. It depends on the call Answer: C
- Which statement about a local variable is correct? A. It can be used anywhere in the program B. It uses memory for the whole time the program is running C. It can be used only within the subroutine it is declared in D. It must be a parameter Answer: C
- What is the difference between a procedure and a function? A. A function returns a value and a procedure does not B. A procedure can take parameters and a function cannot C. A function is always shorter D. A procedure cannot be called more than once Answer: A
- Which is NOT an advantage of using subroutines given in the specification? A. The program runs faster on every machine B. Subroutines can be re-used C. Subroutines can be tested independently D. The structure of the program is clearer Answer: A
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