Unit 4 - Hardware and Software Flashcards

Question

What is Off-the-shelf software?

Answer 1

Off-the-shelf software is a pre-developed, readily available platform designed for a broad user base.

Answer 2

Off-the-shelf software is readily available for anyone to use The cost is usually lower because development costs are shared among all the buyers It is likely to be well-documented and well-tested

Answer 3

You have little or no control over what features there are It may not do exactly what you want

Answer 4

Bespoke software is created to fulfil your own exact specifications

Answer 5

This can significantly increase the cost It may take several weeks, months or even years to develop Complete control over the process gives you all the functionality you need

Answer 6

The true complexities of operations are hidden from the end user via an Application Programming Interface (API). Users can issue commands or simply click a mouse to perform complex operations without having to know how they are carried out. An API acts a bit like a waiter in a restaurant You, the user, look at the menu and give the waiter (the API) your request The waiter takes the request to the kitchen (the operating system) The kitchen sends back the prepared dish via the waiter.

Answer 7

A PC allows many processes to be running at the same time. The OS allocates memory to each process. If there is not enough memory, a program may be swapped out of memory onto disk or “virtual memory” and reloaded when activated.

Answer 8

The OS Controls which programs can send data to the processor to be processed Instructions from multiple operations are queued The processor executes small parts of each operation in turn so that programs appear to run simultaneously This is known as multi-tasking.

Answer 9

The scheduler is the operating system module responsible for ensuring that processor time is used as efficiently as possible

Answer 10

Round Robin – each process in turn has use of the processor for a given time slice Shortest job next Priority system

Answer 11

Windows Task Manager shows the processes that are currently running and the allocation of resources

Answer 12

The OS keeps track of where all files are stored on hard disk or external drives, and where space is free to be used if the user performs a save operation Files can be listed, moved, deleted, protected from unauthorised access

Answer 13

Communicates with I/O devices via the I/O controller, part of the CPU Checks that a required output device is switched on and ready to receive data Deals with processor ‘interrupts’ e.g. an “Out of paper” message from a printer

Answer 14

The first programmable computer. It was programmed using switches and plug panels. Output was an indicator lamp panel. Colossus Mark 1 was developed by Tommy Flowers and built at Bletchley Park in 1943 Input was a continuous loop of paper tape with 20,000 5-bit characters

Answer 15

The code used a Vernam-type cipher and the key changed every day The ciphertext was read in from the paper tape

Answer 16

These early computers had limited memory, with each memory cell consisting of a vacuum tube the size of a light bulb They had a control unit and an accumulator where instructions were carried out They were programmed using machine code, entered using a series of switches

Answer 17

In machine code, a typical instruction holds an operation code (opcode) in the first few bits. It specifies the operation to be performed by the computer's processor.

Answer 18

Address of the address to be used. In machine code, a typical instruction holds an operand in the rest of the bits.

Answer 19

The instruction set of a computer is all the instructions that it can understand and execute If each instruction is held in 8 bits, with 4 bits for the opcode and 4 bits for the operand, the computer can execute 16 different instructions The operand can be either an actual value or the address in memory where the value is held

Answer 20

Each opcode was replaced by a mnemonic which gave a clue as to what the operation did The operand was replaced by a decimal (or hexadecimal) number

Answer 21

It is much easier to write, understand and debug programs in assembly language

Answer 22

The assembly code has to be translated into machine code by an assembler

Answer 23

An imperative high-level language consists of commands for the computer to perform.

Answer 24

A declarative language focuses on what the program should do without listing the steps needed to achieve the result. For example SQL

Answer 25

So that the programmer can think and code in terms of algorithms rather than worrying about how the computer will execute each tiny step.

Answer 26

Much easier and faster to write, debug and maintain programs Different high-level languages have been written specifically for different types of problem High-level language programs are portable – a program written for one type of computer can be recompiled for a different type of computer

Answer 27

The object code (compiled or interpreted code) may run slower than assembly code or machine code The object code may occupy more space in RAM – which can be a problem in embedded systems with a small amount of memory Most high-level languages do not have statements to allow the programmer to manipulate individual bits – essential in some applications, e.g. device drivers

Answer 28

The assembly code program This is the input to the assembler.

Answer 29

The output is the machine code instructions produced by the assembler, called the object code The object code can be saved and run whenever needed.

Answer 30

Assembly code is used when a program needs to execute as fast as possible, occupy as little space as possible or manipulate individual bits and bytes. Typical uses include embedded systems, real-time systems, sensors, mobile phones, device drivers and interrupt handlers. The object code, rather than the source code, is saved and run when required.

Answer 31

A compiler is a complex program which has several phases such as lexical analysis, syntactic analysis, and semantic analysis, going through the whole program at each stage It produces intermediate code, optimises it, then generates the machine code It will not generate the machine code it there are any errors in the program

Answer 32

The compiler will find errors such as syntax errors or missing subroutines When all errors of this kind have been corrected, the compiler will produce relocatable code, since it does not know the absolute addresses where the object code will be loaded The object code can then be saved and the compiler does not need to be present to run the object code

Answer 33

Once a program has been compiled, the object code can be distributed and the compiler is not needed to run the program. The object code runs faster than interpreted code. The object code is more secure, as machine code cannot easily be read and copied by someone wishing to modify the code and sell it as their own product.

Answer 34

An interpreter is useful in education because it allows students to program interactively using “Interactive mode” It is useful during development when a programmer may want to test a small piece of code without recompiling the whole program Both compilers and interpreters are available for most high-level languages

Answer 35

Bytecode is computer object code that an interpreter converts into binary machine code so it can be read by a computer's hardware processor.

Answer 36

OR AND XOR NAND NOT NOR

Answer 37

If one, but not both, of the inputs is 1, the output is 1 Otherwise the output is 0

Answer 38

It inverts the output of the AND gate

Answer 39

This gate inverts the OR gate The output is 1 only if both inputs are 0

Answer 40

Using only NAND gates to build a circuit can minimise cost of production Using as few gates as possible can speed up processing

Answer 41

If 0 is input it outputs 1 If 1 is input it outputs 0

Answer 42

If both inputs are 1 then the output is 1 Otherwise the output is 0

Answer 43

If either input is 1 then the output is 1 Otherwise the output is 0

Answer 44

This states that (NOT A) . (NOT B) = (NOT A+B)

Answer 45

This states that: (NOT A.B) = (NOT A) + (NOT B)

Answer 46

𝐴+𝐵=𝐵+𝐴 A.𝐵=𝐵.𝐴

Answer 47

(𝐴.𝐵).𝐶=𝐴.(𝐵.𝐶) (𝐴+𝐵)+𝐶=𝐴+(𝐵+𝐶)

Answer 48

𝐴.(𝐵+𝐶)=𝐴.𝐵+𝐴.𝐶 (𝐴+𝐵).(𝐴+𝐵) = 𝐴.𝐴 + 𝐵.𝐵 + 𝐴.𝐵 + 𝐴.𝐵

Answer 49

A+𝐴.𝐵=𝐴 A.(𝐴+𝐵)=𝐴

Answer 50

- A half adder has two bits as inputs (A and B) and adds the two bits and outputs two bits the sum (S) and the carry (C). It is made up of an AND and an XOR gate

Answer 51

A full adder has three bits as inputs one of which is the carry bit. It adds the three bits and outputs two bits the sum (S) and the carry (C). It is made up of an AND, XOR and OR gates

Answer 52

A flip-flop can store the value of a bit. * D (delay)-type flip flops are used to store one bit and flip between two states: 1 and 0. * The inputs are a control value (0 or 1) and also a clock value (0 or 1) that changes the state at a regular rate. * For a positive edge triggered flip-flop the output state can only change when the clock changes from 0 to 1. If D is in the same state as it was on the previous edge then the output is unchanged. However, if D has changed state, the output state will change to the value of D.