Grade 11 IB Computer Science SL
Test #2
Topic 1.2 - System design basics: 1.2.1 - 1.2.3
Topic 2.1 - Computer Organisation: 2.1.1 - 2.1.5
Topic 4 - Introduction to programming: 4.3.1 - 4.3.9
Date: Monday 7 November, 2022
Name:Markscheme
Computer science
Standard level/Higher level
Paper 1
Time allowed: 55 minutes
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Instructions to candidates
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Do not open this examination paper until instructed to do so.
Section A: answer all questions.
Section B: answer all questions.
The maximum mark for this examination paper is [40 marks].
Section A:
/34
Section B:
/6
Total:
/40
Section A
1. Identify two essential features of a computer language.
[2]
Award up to [2 max].
Fixed vocabulary;
Unambiguous meaning;
Consistent grammar;
Consistent syntax;
Provide a way to define basic data types and operations on those types (ability to
write functions/procedures);
Provide ability of Input and output handling;
Provide some kind of loop that can be stopped / conditional statement / branching
(conditional and unconditional branching);
It should have variables that reference computer memory, syntax for basic arithmetic
and logical;
Operations on those memory locations;
It has to run on/be able to be processed by a computer (ie it must have a
compiler/interpreter)
Note: do not accept aspects that address interoperability/portability/standards/user
friendliness [2]
2. Two fundamental operations of a computer are add and retrieve.
State another two fundamental operations.
[2]
Compare (accept Check);
Store (accept Write / Save)
Note: Accept the following wording for categories of operations
Input (Read);
Processing/execution (eg calculate, decode, fetch, delete, evaluate, sort, transfer,
transmit);
Output;
Control;
Remark: Beware of repetitions with the wording in the question paper, or repetitions
between the two given examples. Marks should not be awarded twice in those
cases.
For example
Search/look up, or comparable wording, are synonyms of the given Retrieve;
Insert/put, or comparable wording, are synonyms of the given Add;
Lists of repeated arithmetic operations that fall under examples of calculations
(subtract,
divide, multiply, square) are all examples of calculations, and hence processing. [2]
2
3. (a) State the purpose of cache memory.
[1]
Is used to save time in accessing RAM; [1]
(b) Draw a diagram to show the relationship between random access
memory (RAM), the processor and cache memory.
[1]
4. Describe the function of the control unit (CU) in the central processing
unit (CPU).
[2]
Award up to [2 max].
Obtains the data/instructions from the memory;
Interprets/decodes them into commands/steps/signals;
Controls transfer of data and instructions among other units of a CPU (for example,
command to ALU for execution);
Manages/coordinates all the units of the computer; etc. [2]
5. Describe a disadvantage of the use of virtual memory.
[2]
Award [1 mark] for naming the disadvantage and [1 mark] for an explanation up to [2
marks max].
Possible answers (there may be others)
Performances drop;
Because of the time to switch among applications;
The time to search/access files on the hard disk;
Access speed of secondary memory versus primary;
May require more HW;
Because part of the hard disk is reserved to virtual memory, hence additional storage
space might be necessary;
Increase power consumption;
Because the overall processing time slows down; [2 marks]
3
6.
Consider the following algorithm written in pseudocode:
sum = 0
count = 1
num = input
loop A from
num =
sum =
end loop
("Enter an integer")
1 to 3
num + 1
sum + num
output sum
What will be output if num = 2?
Show your working.
[3]
Output = 12
[1] Add 1 to the number
[1] Sum the numbers
[1] Loop 3 times
7. Write pseudocode to:
Input the dimensions of a rectangle and print the area and perimeter.
[3]
output "Program to calculate the area and perimeter of a rectangle"
output ""
a = input ("Enter the length of the rectangle")
b = input ("Enter the width of the rectangle")
perim = 2 * a + 2 * b
area = a * b
output "The perimeter is: ", perim
output "The area is: ", area
[1] - inputs
[1] - formulas
[1] - outputs
4
8. Write pseudocode using if and else to:
Input 3 numbers (a, b and c), and print the largest.
[5]
Output “Program to find the largest of 3 numbers”)
a = input ("Enter your first number")
b = input ("Enter your second number")
c = input ("Enter your third number")
if a > b then
biggest = a
else
biggest = b
end if
if c > biggest then
biggest = c
output "The biggest number is", c
else
output "The biggest number is", biggest
end if
[1] Input
[2] if loops
[1] output
[1] logic correct
9. What does the following code print?
[2]
if 4 + 5 == 10:
output ("TRUE")
else:
output ("FALSE")
output ("TRUE")
FALSE
TRUE
5
10. What is the output of the following code?
[2]
loop X from 1 to 5
if X mod 2 = 0 then
output "even"
else
output "odd"
end if
end loop
odd
even
odd
even
odd
11(i) The given flowchart models the generation of some
numbers in a certain range. Write the first two and the last
two numbers that it generates.
[4]
1, 3 36, 45
(ii) Write pseudocode that corresponds to the logic indicated
by the flowchart.
[3]
X=1
T=1
loop until T > 50
output T
X=X+1
T=T+X
end loop
(iii) State how to modify the given flowchart to display the number
sequence 1, 4, 9, 25, 36, 49.
[2]
T = X ** 2
6
Section B
9. A new higher level programming language is being developed.
(a) Identify two reasons why consistent grammar and syntax should
be essential features of a higher level programming language.
[2]
a) Award up to [2 max].
Easy to learn/use;
Otherwise time may be wasted learning the new language/writing programs in
this HLL;
There will be no/less compilation errors;
There will be no/less logical errors;
(Reduction of time to create software;)
Future maintenance/development is possible by other programmers; [2]
Application programmers who use this programming language will be able to
choose to use either an interpreter or a compiler.
(b) (i) Outline the need for an interpreter or a compiler.
[2]
Award up to [2 max].
Must be translated from a higher level language understandable by humans/not
understood by machines;
Must be translated into machine code;
For the CPU to execute it; [2]
(ii) Describe one advantage to application programmers of having both an
interpreter and a compiler available.
[2]
Award up to [2 max].
Interpreter is faster/immediately warns about syntax errors/executes commands and
they could use it instead of the compiler while coding and debugging their programs;
Compiler is required when there is a need to produce an executable version of a
program; [2]
7