Structured Programming (AQA GCSE Computer Science)

Explain one advantage of the structured approach to programming.

A REPEAT…UNTIL iteration structure was used in Figure 9.

Figure 9

SUBROUTINE calculate(n)
   a ← n
   b ← 0
   REPEAT
     a ← a DIV 2
     b ← b + 1
   UNTIL a ≤ 1
   OUTPUT b
ENDSUBROUTINE

Figure 10 shows another subroutine called calculate that uses a WHILE…ENDWHILE iteration structure.

Figure 10

SUBROUTINE calculate(n)
   a ← n
   b ← 0
   WHILE a > 1
        a ← a DIV 2
        b ← b + 1
   ENDWHILE
   OUTPUT b
ENDSUBROUTINE

One difference in the way the subroutines in Figure 9 and Figure 10 work is:

• the REPEAT…UNTIL iteration structure in Figure 9 loops until the condition is true

• the WHILE…ENDWHILE iteration structure in Figure 10 loops until the condition is false.

Describe two other differences in the way the subroutines in Figure 9 and Figure 10 work.

The size of a sound file is calculated using the following formula:

size (in bits) = sampling rate sample resolution seconds

To calculate the size in bytes, the number is divided by 8

The algorithm in Figure 12, represented using pseudocode, should output the size of a sound file in bytes that has been sampled 100 times per second, with a sample resolution of 16 bits and a recording length of 60 seconds.

A subroutine called getSize has been developed as part of the algorithm.

Complete Figure 12 by filling in the gaps using the items in Figure 11.

You will not need to use all the items in Figure 11.

Figure 11

Figure 12

SUBROUTINE getSize(____________, ____________, seconds)

         ______________ ← sampRate  *   res  *    seconds

         size ← ______________

         ______________ size

ENDSUBROUTINE

OUTPUT ______________(100, 16, 60) 

State three advantages of using subroutines.

State two benefits to the developer of using the three separate subroutines described in Figure 2 instead of writing the program without using subroutines.

Figure 2

State two benefits of developing solutions using the structured approach.

A developer is writing a program to convert a sequence of integers that represent box playing cards to Unicode text.

The developer has identified that they need to create the subroutines shown in Figure 2 to complete the program.

Figure 2

Explain how the developer has used the structured approach to programming.

Figure 3 shows the subroutine convert described in Figure 2.

Some parts of the subroutine have been replaced with the labels L1 to L5.

Figure 3

SUBROUTINE convert(cards)
   result ← ''
   max ← LEN(cards)
   index ← 0
   WHILE index < L1
     rank ← L2(cards[index])
     suit ← getSuit(cards[L3 + 1])
     c ← rank + ' of ' + suit + ' '
     result ← result + L4
     index ← index + 2
   ENDWHILE
   RETURN L5
ENDSUBROUTINE

State the pseudocode that should be written in place of the labels in the subroutine written in Figure 3.