Iteration (Ch2) (M2)

Question 1

What is iteration?

Answer 1

Iteration is the act of repeating a process until there is a desired result

Question 2

When is iteration needed?

Answer 2

Iteration is needed when producing an algorithm because it means that you don’t have to write the same thing out lots of times - it makes code more efficient

Question 3

What is definite iteration?

Answer 3

Definite iteration is where the number of iterations is known before the execution

Question 4

What are the two examples of definite iteration?

Answer 4

Examples of definite iteration: FOR, IF

Question 5

What do IF statements allow you to do?

Answer 5

IF statements allow you to check if a condition is true or false, and carry out different actions depending on the outcome.

Question 6

What do nested IF statements allow you to do?

Answer 6

Nested IF statements allow you to check more conditions once you’ve established that the previous condition is true.

Question 7

How are IF-ELSE-IF statements different from nested IF statements?

Answer 7

IF-ELSE-IF statements are different from nested IF statements as they only check more conditions if the previous condition is false.

Question 8

What is a nested IF statement?

Answer 8

A nested IF statement is one IF statement inside of another one

Question 9

What do FOR loops do?

Answer 9

FOR loops will repeat the code inside them a fixed number of times.

Question 10

The number of times that a FOR loop repeats depends on what?

Answer 10

The number of times that the code repeats will depend on:

An intitial value, end value and the step count.

Question 11

What is stepping used for in loops?

Answer 11

Stepping is used to move through a loop by different amounts

Question 12

What is indefinite iteration?

Answer 12

Indefinite iteration is where the number of iterations isn’t known before the execution

Question 13

Where are while loops controlled by a condition?

Answer 13

While loops are controlled by a condition at the start of the loop.

Question 14

If the condition is false, what happens to the code inside of a while loop?

Answer 14

If the condition is false, the code inside a while loop is never run

Question 15

If the condition is true, what happens to the code inside of a while loop?

Answer 15

If the condition is true, the code inside a while loop is always run

Question 16

Where is the condition controlled in a DO UNTIL loop?

Answer 16

DO UNTIL loops are controlled by a condition at the end of the loop

Question 17

What is the difference between a WHILE and DO UNTIL loop?

Answer 17

The difference between a WHILE and DO … UNTIL loop is:

A DO … UNTIL loop does the comparison at the end of the block, but a WHILE loop does it at the start of the block.

Question 18

How many times at least, does a DO UNTIL loop run?

Answer 18

DO UNTIL loops always run the code inside them at least once

Question 19

If the condition is never true, what happens to the DO UNTIL loop?

Answer 19

If the condition is never true, the loop is infinite

Question 20

DO UNTIL loops continue until what?

Answer 20

DO UNTIL loops continue until the conditon is true

Question 21

What is a nested loop?

Answer 21

A nested loop is when at least one loop exists inside another loop

Question 22

What is a dry run?

Answer 22

A dry run is where the program is run on paper and is carefully analysed to fix any errors.

Question 23

What is a trace table?

Answer 23

A trace table is a table which shows the values of each variable, input and output and how they change. This is made while a dry run is being worked through.

Question 24

Trace tables make sure there are no type of what error?

Answer 24

Trace tables make sure there are no logic errors

Question 25

What do the columns and rows of a trace table usually represent?

Answer 25

The columns of a trace table usually represent variables. Each row of a trace table represents the values that the variables take at a particular point in the algorithm.

Question 26

If not variables, what can the columns of a trace table represent?

Answer 26

The columns of a trace table might not always be variables - they could be any information that the programmer is interested in.

Question 27

When testing a larger program, what will a tester often use?

Answer 27

When testing a larger program, the tester will often use debugging tools.

Question 28

What is a syntax?

Answer 28

A syntax is a set of rules

Question 29

What are syntax errors usually pointed out by?

Answer 29

Syntax errors are usually pointed out by the IDE

Question 30

What happens to programs with syntax errors?

Answer 30

Programs with syntax errors will not run

Question 31

Give one example of a syntax error

Answer 31

Examples of syntax errors include:

Wirteline instead of writeline
Missing bracket or speech mark
Forgetting to end an IF statement

Question 32

What is a logic error?

Answer 32

A logic error is a mistake in the code that causes it to perform in an unexpected way.

Question 33

What happens to programs with logic errors? Why is this a problem?

Answer 33

Programs with logic errors will still run. This makes logic errors hard to spot and makes them sometimes go unnoticed

Question 34

Give one example of a logic error

Answer 34

Examples of logic errors include:

Using and instead of or
Using > instead of >=
Forgetting to add VAT if calculating a total cost that should include VAT