Download Various Questions and Answers

F453 Computing
Questions and Answers
Explain why interrupts are used in a
computer system (2)
Interrupts are used to obtain processor time for a higher priority task. They are
also used to avoid delays.
Other answers include:

Avoid loss of data

As an indicator to the processor

That a device needs to be serviced
State two sources of interrupts and
explain why these sources have
different job priorities (4)

SOURCE 1 – User interrupt – for example new user log on request

SOURCE 2 – Power Failure/system failure
REASON – New user can wait but the data must be saved before the power
fails.
Other answers include:

Clock interrupt

Software interrupt

Peripheral interrupt i.e.. Printer empty.
Describe two reasons why scheduling
is used.

Maximise number of users…


with no apparent delay
Maximise number of jobs processed…

As quickly as possible.
Other answers include

Obtain efficient user of processor time dependant upon priorities
Explain why jobs are given different
priorities when in a job queue. (2)

Some jobs are more urgent than others

Priorities are used to maximise the use of computer resources
Assembly language and machine code are
languages used in computing. Describe the term
assembly language (2)

It is a lower level language/machine specific that uses descriptive names
for data stores and mnemonics for instructions.
Other answers include
Uses labels to allow selection
Each instruction is generally translated into one machine code instruction
May use Macros
Describe the term Machine Code (2)

Binary notation

Where instructions operate on bytes of data
Other answers include

Set of all instructions available

To the architecture.
State three of the tasks performed by
an assembler when producing
machine code. (3)

Reserves storage space for instructions and data

Replaces mnemonic opcodes by machine codes

Create symbol table to match label to addresses

Checks syntax
Either an interpreter or compiler may
be used with a HLL program. Describe
one feature of an interpreter. (2)

Translates one line/statement…


Then allows it to be run before translation of the next line OR
Reports error at a time..

And stops.
State two features of a compiler (2)

Translates whole program as a unit

Creates executable program/intermediate program

Other answers include:

May report a number of errors at the same time

Optimisation.
Lexical analysis is one stage of
compilation. Describe what happens
during lexical analysis. (8)






Once the programmer has written the code, the source program is
then used as the input
and tokens are created from individual symbols and from the
reserved words in the program.
Tokens are a fixed length string of binary digits. Once this has
taken place, the
variable names are loaded into a symbol table and
all redundant characters such as spaces and comments are
removed. The final stages of this involves
error diagnostics and the code is then prepared for the syntax
analysis.
State the three stages in order, of the
machine cycles in classic Von
Neumann Architecture. (2)

Fetch Decode Execute
Two computer architectures are reduced instruction set
computer (RISC) and Complex instruction set computer
(CISC) architectures.
Complete the table below.
Compare the number of machine cycles
used by RISC and CISC to complete a
single instruction (2)

RISC – each task may take many cycles

CISC – a task may be completed in a single
cycle
 As
instructions may be more complex that individual
instructions in RISC
An array processor is used in some systems.
Explain the term array processor. (2)

A processor that allows the same instruction to operate
simultaneously

On multiple data locations
Other answers include:

The same calculation on different data is very fast

Single instruction multiple data.
Give one example of the type of task for which
an array processor is most suitable (1)
 Weather
forecasting or
 airflow simulation around new
aircraft.
A list of cities is: Aberdeen, Belfast, Cardiff, Glasgow,
Oxford, York.
Show the steps of a serial search for York in the list. (2)

Start at Belfast

Look at each word in turn

Until York is found.
A list of cities is: Aberdeen, Belfast, Cardiff, Glasgow,
Oxford, York.
Show the steps of a binary search for York in the list. (3)

Look at the middle (Cardiff. Glasgow,)

York is in second half of list

Repeat halving

Until York is found.
Explain one advantage of a binary search
compared with a serial search when searching
for an item in any large set of data (3)

Usually faster because

Half the data is discarded at each step/fewer items are checked.
A stack contains a number of data items. List the
steps needed to attempt to add one data item
to the stack. (3)
 If
stack is full
 Report
error and stop
 Increment
 Add
pointer
data item at position ‘pointer’
Explain how a quick sort can be used to put a set
of numbers into ascending numerical order. You
may use the following set of numbers: 30 9 46 14
22 (5)
Give the name for one other method
of sorting used in computing (1)
Insertion
sort
State the traversal that should be used
to obtain the reverse polish notation
form from a binary tree. (1)
Post
order
Other than a binary tree, state what
data structure may be associated with
RPN (1)
Stack
State a symbol, often used in
mathematical expressions that is not
required when working with RPN
Brackets
A program in a particular assembly language includes the instructions:
JMP CD (jump to instruction labelled CD) and CD ADD 41 ( add
number 41 to number in accumulator) Explain the term opcode and
give one example from information given. (2)

Opcode is the mnemonic part of the instruction and it indicates what is it
to do.

The example given is JMP/ADD
State the type of addressing used by
the instruction AND 41 (1)
Immediate
State the meaning of the term
symbolic addressing and give one
example from the information given.

The use of characters to represent the address
of a store location.

The example is CD.
Explain the purpose of the
accumulator (2)

Temporary storage within ALU and it holds the data being processed.
IT also deals with the input and output in the processor.
Describe indexed addressing (3)

Uses the index register and an absolute address to calculate addresses to
be used
State the meaning of direct
addressing (1)

Instruction gives to address to be used.
Explain why it is not possible to only use
direct addressing in assembly languages
(2)

Because the number of addresses available is limited by the size of the
address field.

Code is not relocatable.
Explain the term data dictionary and
give two examples of the information
stored.(4)
A data dictionary is a file containing descriptions of data in the database
it is used by database managers when altering the database structure.
It may include names of tables/columns and may define access rights.
Other examples may include:

Identifies foreign keys

Identifies indexes

Meaning of data columns

Relationship between data.
It has been decided to start selling pet toys. Details of toys
and their suppliers need to be added to the database.
State the language used to create the table TOY (1)
 Data
description Language DDL
Give three benefits to a relational
database compared with flat files. (3)

Avoid data duplication

Easier to change data

Data can be added easily