Algorithms 1

Question 1

Describe how the linear search algorithm works.

Answer 1

Start at the beginning of the array, then compare each element until the value being searched is found or until the end of the array.

Question 2

code ← '' 
i←0
WHILE instr[i] ≠ ':' AND i < 4 
code ← code + instr[i]
 ENDWHILE
 valid ← False
 IF code = 'ADD' OR code = 'SUB' OR code = 'HALT' THEN
 valid ← True
ENDIF

Shade one lozenge to show the most appropriate data type of the variable i in the algorithm.

Answer 2

integer

Question 3

code ← '' 
i←0
WHILE instr[i] ≠ ':' AND i < 4 
code ← code + instr[i]
 ENDWHILE
 valid ← False
 IF code = 'ADD' OR code = 'SUB' OR code = 'HALT' THEN
 valid ← True
ENDIF

state the data type of the variable ‘valid’ in the algorithm

Answer 3

Boolean

Question 4

State the final value of the variable ‘valid’ in the algorithm for the following different starting values of instr.

Answer 4

False
True
True

Question 5

State what an assembly language program must be translated into before it can be executed by a computer.

Answer 5

Machine code

Question 6

State two reasons why a programmer, would usually choose to develop in a high level language rather than a low level language.

Answer 6

1. (High-level languages) are easier to understand/read

2. High level languages are easier to debug.

Question 7

The algorithms in Figure 4 and 5 have the same purpose

State this purpose

Answer 7

To multiply the value in number by 3

Question 8

Explain why the algorithm shown in Figure 4 can be considered to be more efficient algorithm than the algorithm shown in Figure 5

Answer 8

Algorithm in figure 4 uses less variables

Question 9

Show the steps involved to bubble sort the array shown.

8,4,1,5

Answer 9

8,4,1,5
4,8,1,5
4,1,8,5
4,1,5,8
1,4,5,8
1,4,5,8

Question 10

Complete the table showing all the outputs from the subroutine call main (3)

Answer 10

10
5
16
8
4
2
1

Question 11

Describe how the developer has used the structured approach to programming in Figure 7

Answer 11

The developer has used local variables

The developer has used parameters

Question 12

Shade one lozenge to show what value would be returned from the subroutine call CODE_TO_CHAR(100)

Answer 12

B - ‘d’

Question 13

State the value that will be returned from the subroutine call
CODE_TO_CHAR(CHAR_TO_CODE(‘E’)+2)

Answer 13

G;

Question 14

A developer needs to store data about thousands of songs in a program. She needs to be able to hold information on every song’s title, singer, and year of release.
Explain how the developer could use a combination of an array and records to store this information.

Answer 14

An array could be used to store all the songs
A record could be used to store data for one song.

The singer could be a string
the year of release could be a integer
the song title is a string