Mock Revision

Question 1

What is a FAT?

Answer 1

A map of where files are stored. Also contains various metadata, such as file names, access rights, and file sizes. It is used by the operating system when files are saved, deleted and accessed

Question 2

What is a BIOS? What does it do?

Answer 2

BIOS (basic input/output system) is the program a personal computer’s microprocessor uses to get the computer system started after you turn it on. It also manages data flow between the computer’s operating system and attached devices such as the hard disk, video adapter, keyboard, mouse and printer.

Question 3

What is a TCP/IP

Answer 3

Transmission Control Protocol/Internet Protocol

TCP governs how messages are prepared and, once they’re received, it governs how they are decoded.

Steps for sending data:
- Divide the message into chunks of data called “packets”.

• Add a sequence number to each packet. This lets the receiving computer know what order the packets are supposed to be re-assembled in.
• Add error-correction data, so errors introduced during transmission can be spotted and fixed

Steps for receiving data:

• Examine each packet for errors by using the extra information that was added to it
• Fix errors (if possible) or request that the packet be re-sent
• Identify missing packets and request them to be re-sent
• Reassemble the message in the correct order, using the sequence number of each packet
• Send the message on to the correct application. Emails go to the email application, web pages go to the browser, etc.

Question 4

What is an interrupt and what does it do?

Answer 4

Interrupts are used to tell the processor to stop what it is doing because there is something more important which needs dealing with.

Before FDE Cycle, CPU checks contents of interrupt register. If there is an interrupt in the IR with higher priority than the current task, then the interrupt is processed.

Question 5

What are the goals of a scheduler?

Answer 5

• To make efficient use of processor time
• To make efficient use of resources
• To maximise the number of users without apparent delay
• To maximise the throughput of the CPU

Question 6

How does Round Robin Scheduling work?

Answer 6

Each task is given a small “time slice” - perhaps of a few milliseconds. After the time is up, the processor moves on to the next task.

Question 7

How does Shortest Job First work?

Answer 7

The shortest job is processed first. Although this leads to lots of jobs being done quickly, it can lead to some longer jobs never getting processed.

Question 8

How does Shortest Time Remaining work?

Answer 8

The job with the least time remaining is processed first. This is similar to shortest job first, although it is considered sightly superior because long jobs will slowly “bubble up” until they have the shortest time remaining.

Question 9

How does First Come First Served the first work?

Answer 9

The first job to be ready for processing is processed.

Question 10

How does Multi-Level Feedback Queues

Answer 10

A number of queues are set up. If a task actively uses large amounts of processor time, it is placed in a lower priority queue, until it reaches the “base” queue, which operates in a round robin fashion.

Question 11

What is Machine Code?

Answer 11

Machine code consists of all the possible instructions for a particular processor. The code is often very hard for humans to understand and write without mistakes, because it is encoded in binary.

Question 12

What is an assembler?

Answer 12

An assembler then “assembles” the program from assembly language into machine code. One assembly language instruction is translated into one machine code instruction. A symbol table is created to match labels to addresses. Finally, the syntax is checked, and diagnostics are offered for errors (if any).

Question 13

What is lexical analysis?

Answer 13

Lexical analysis takes the source program, strips out comments and whitespace, and replaces reserved words and symbols used in the program with tokens (fixed length strings of binary digits). Variable names are stored for later use and error messages are output if necessary.

Question 14

What is syntax analysis?

Answer 14

Syntax analysis is where the token stream is verified against the syntax rules of the programming language. Consider the token stream above. It reads:

Question 15

What is code generation?

Answer 15

Code generation is where code is actually converted into machine code (which can be executed).

During code generation, the code can be optimised - either for smallest code size, or fastest performance, or to improve some other aspect of the code.

Question 16

Array

Answer 16

An array processor has a number of Arithmetic Logic Units (ALU) that allows all the elements of an array to be processed at the same time.

Question 17

What is a register?

Answer 17

A register is a discrete memory location within the CPU designed to hold temporary data and instructions

Question 18

What does the Program Counter do? (PC)

Answer 18

Contains the memory address of the next instruction to be executed. It is automatically incremented.

Question 19

What does the Current Instruction Register do? (CIR)

Answer 19

This holds the current instruction to be executed, having been fetched from memory.

Question 20

What does the Memory Address Register do? (MAR)

Answer 20

Contains the memory address of the next piece of memory to be fetched.

Question 21

What does the Arithmetic Logic Unit do? (ALU)

Answer 21

It allows for logical decisions to be made.

Question 22

What does the Accumulator do? (ACC)

Answer 22

The accumulator is a section of the arithmetic unit where intermediate arithmetic and logic results are stored.

Question 23

What is the Von Neuman Architecture?

Answer 23

It consists of a single processor which fetches, decodes, and executes instructions one at a time (the “FDE cycle”).

Current Instruction Register (CIR) - contains the instruction currently being executed.

Fetch: The PC holds the address of the next instruction. This address is copied to the MAR, and the contents of that address are copied to the MDR and the CIR. The PC is then incremented.

Decode: The contents of the CIR are “decoded” into instructions which the control unit can interpret, so that the processor “knows” what to do.

Execute: The memory address of any data needed to execute the instruction is copied from the CIR to the MAR. The data found at this address is copied to the MDR, and then the data is used.

Question 24

The three busses?

Answer 24

Data bus - carries data from one part of the computer to another.

Address bus - carries the address to which the data (in the data bus) should be delivered. Both the address and the data travel together until the correct component identifies its address, and collects the data being transported.

Control bus - carries commands from the control unit to other devices.

Question 25

What does the Memory Data Register (MDR) do?

Answer 25

Holds the data that has been fetched from memory.

Question 26

What is insertion sorting?

Answer 26

The insertion sort “steps” through the list, inserting each item in term into the correct position (relative to the “sorted” items before it). The insertion sort is simple to implement, and generally quicker for small datasets than a quick sort.

Question 27

What’s a linked list?

Answer 27

Every item in a linked list has a pointer. The pointer “points” to the next entry in the list. A pointer known as a “terminator” represents the end of the list. This means that the data does ` Qnot have to be stored in a “block”, but can be scattered. It also allows the data (but not the structure) to be changed after the structure is created.

Question 28

What’s a hash table?

Answer 28

Hash table is a type of data structure. It allows data of any size to be mapped with a related but fixed size form.

Question 29

What’s Procedural programming?

Answer 29

Procedural programming languages separate data and code. Code is usually modularised and a combinations of sequence, selection and iterative constructs. The programmer describes how to solve the problem, by specifying the steps to execute a program and the order they should be carried out.

Question 30

What’s Object oriented programming?

Answer 30

Object oriented programming is where objects combine methods and data.

Data encapsulation - this means that data can only be accessed via methods provided by objects.
Class - acts as a template for an object. Contains shared attributes and methods.
Object - an individual instance of a class.
Derived class - a class with all the features (including attributes and methods) of a superclass and additional features specific to the derived class. This is an example of inheritance.

Question 31

What’s a parameter?

Answer 31

Data supplied to a function which is used as a local variable.

Question 32

What’s a local variable?

Answer 32

Defined and only accessible within one module of a program. Data is lost once execution of the module is completed. The same (local) variable names can be used in different modules.

Question 33

What’s a global variable?

Answer 33

Defined at the start of the program and exists until the program finishes. Data can be shared between modules using global variables, but they are overridden by local variables with the same name.

Question 34

What’s iteration?

Answer 34

A type of programming construct which involves repeating a section of a program until a condition is met. The section might not be executed if the condition is already met.

Question 35

What’s SQL?

Answer 35

Structured Query Language - Database Management System

Question 36

What is referential integrity?

Answer 36

It is the term used to describe when all the links between tables using foreign keys are present and valid

Question 37

What’s pipelining?

Answer 37

Pipelining is the technique of fetching an instruction whilst the prior one is being decoded and the one before that is being executed.

Question 38

What’s abstraction?

Answer 38

Abstraction is the act of representing essential features without including the background details or explanations