02 Section 5 - Sub programs

Question 1

What are procedures?

Answer 1

Procedures are sets of instructions stored under one name

-when you want a program to do a whole set of instructions you only need to call the procedure

Question 2

What are functions?

Answer 2

Functions are sets of instructions stored under one name WHICH WILL ALWAYS RETURN A VALUE

Question 3

What are the advantages of procedures and functions?

Answer 3

• help avoid repeating code
• useful when you have sets of instructions that repeat in different places throughout a program
• gives a program more structure
• makes a program more reliable
• cuts down the amount of code you have to write

Question 4

Why would you create your own procedures or functions since high-level languages have common procedures and functions built into them?

Answer 4

-if you want one that will do something more specific

Question 5

What do most sub-programs contain?

Answer 5

parameters

arguments

Question 6

What are parameters?

Answer 6

Parameters are special variables used to pass values into a sub program
-you can specify a name, data type and default value for each parameter

Question 7

What are arguments?

Answer 7

Arguments are the actual values that the parameters take when the sub program is called

Question 8

What are the features of procedures?

Answer 8

• don’t have to take parameters (sometimes will)
• called by typing their name (and giving an argument is necessary)
• procedures don’t return a value

Question 9

What are the features of functions?

Answer 9

• take at least one parameter and must always return a value
• when a function is called it should be assigned to a variable or used in a statement, otherwise the returns will not be stored anywhere and will be lost

Question 10

What are the two types of variables you can have?

Answer 10

Either local or global

-all variables have scope

Question 11

What does a variables scope tell a programmer?

Answer 11

The scope of a variable tells you which parts of the program the variable can be used in

Question 12

What are local variables?

Answer 12

Variables that can only be used within the structure they are declared in
-they have local scope

Question 13

What are global variables?

Answer 13

Variables that can be used any time after their declaration

-they have global scope

Question 14

When are variables local?

Answer 14

When they are declared within a sub program

-they are invisible to the rest of the program (can’t be used outside of the function)

Question 15

What are the advantages of local variables?

Answer 15

• their scope only extends to the sub program they are declared in
• they can’t affect and are not affected by anything outside of the sub program
• it doesn’t matter if you use the same variable name as a local variable elsewhere in the program

Question 16

How can variables in the main body of a program be made into global variables?

Answer 16

using the keyword ‘global’

-they then can be used anywhere in the program

Question 17

What is a disadvantage of global variables?

Answer 17

It can be difficult to keep track of the value assigned to the global variable in larger programs