Topic 3 : Computers

What is the von Neumann stored program concept?

A computer architecture design where both data and instructions are stored together in the same main memory (RAM) and fetched by the CPU

Name the 6 common CPU components

1. Control Unit (CU)

2. Arithmetic logic unit (ALU)

3. Registers

4. Cache

5. Buses

6. Clock

What is the role of the Arithmetic Logic Unit (ALU)?

It performs all the arithmetic calculations (addition, subtraction etc) and logical decisions (AND, OR, NOT)

What is the function of the control unit (CU)?

It coordinates and manages the CPU’s activities, directing the flow of data, and deciding instructions

What is the purpose of the CPU’s clock?

It sends out a continuous pulse (signal) to synchronise the timing of all internal components and operations

Define a CPU register

A location of extremely fast, temporary storage directly inside the CPU used to hold single instructions or data items currently being processed

What are the 5 registers in a CPU

1. Program counter

2. Memory address register (MAR)

3. Memory data register (MDR)

4. Current instruction register (CIR)

5. Accumulator (ACC)

What is the function of the program counter?

Holds the memory addresses of the next instruction to be fetched from main memory

What is the function of the MAR?

Holds the address of the current instruction that is to be fetched from memory to which data is to be transferred

What is the function of the MDR?

Holds the contents found at the address held in the MAR, or data which is to be transferred to main memory

What is the function of the CIR?

Holds the instruction that is currently being decoded and executed

What is the function of the accumulator?

Hold the results of processing

What is a cache?

A small amount of high speed memory built directly within the processor. Used to temporarily hold data and instructions the processor is likely to reuse

Name the three buses in the CPU and state their roles

1. Address bus - carries memory addresses from the CPU to RAM (unidirectional)

2. Data bus - Transfers data/ instructions between the CPU and memory/ devices (bidirectional)

3. Control bus - carries control and command signals to coordinate computer activities (bidirectional)

Describe the steps of the Fetch - Decode - Execute (FDE) cycle

1. Fetch - the next instruction is retrieved from main memory (RAM) via the buses into the CPU

2. Decode - the Control unit (CU) interprets the instruction to find out what action needs to be taken

3. Execute - the instruction is carried out (calculation by the ALU or data loading)

What is memory?

The component of a computer that holds data and programs

What are the 3 types of main memory?

1. RAM - random access memory

2. ROM - read only memory

3. Cache memory

Which of these are volatile?

RAM and cache memory

Which of these are non- volatile?

ROM

What is an example of a program stored in ROM?

BIOS - basic input output system : checks if hardware is functioning correctly once computer is turned on, then computers OS. Because it is always needed, it is stored in ROM.

What is the main structural difference between RAM and ROM?

RAM is volatile (loses data when powered off) and read/ write; ROM is non-volatile(retains data when powered off) and read-only.

What are the purposes of RAM and ROM in a system?

RAM stores the operating system, currently running applications, and active data. ROM stores the bootstrap loader (the initial bootup/ startup instructions for the computer)

Why is secondary storage needed?

For permanent, non-volatile storage of files, programs and data when the computer is turned off.1

What are the three types of secondary storage technologies?

1. Magnetic - hard disk drive

2. Optical - DVD/ Blue-ray

3. Solid-state - SSV, USB flash drive

Compare solid-state vs magnetic storage on speed and durability

Solid-state is much faster and more durable (no moving parts) but more expensive per gigabyte; Magnetic is slower and prone to physical shock but cheaper for higher capacities

What is a general purpose computer?

A computer designed to be able to carry out a wide range of instructions

What is an embedded system?

A dedicated, single-purpose computer system built inside a larger mechanical or electrical device (e.g., washing machine, microwave)

What is the primary role of the Operating system (OS)?

It manages the computer’s hardware components, resources, memory and security, while providing a user interface (UI) for the user to interact with.

Define Utility Software

Systems software designed to help maintain, configure, optimise or analyse a computer system (e.g., defragmentation tools, antivirus tools, file compression)

What is the difference between a high-level and low-level programming language?

1. High-level languages are abstract, use English-like syntax, and are easy for humans to read/ write. (Python)

2. Low-level languages are close to hardware instructions, execution-efficient, but complex to write. (Assembly, machine code)

What does an Assembler do?

It translates Assembly language code into machine code (binary instructions that the CPU can execute directly)

Explain how a compiler works, including its main advantages and disadvantages

It translates the entire high-level code into machine code all at once

Advantage : code runs very fast after compilation

Disadvantage : finding band fixing errors takes longer as the whole code must recompile

Explain how an interpreter works, and its main advantages and disadvantages

It translates and executes high-level source code line by line

Advantage : excellent for debugging; errors are spotted instantly on the exact line they happen

Disadvantage: programs run slower because the code must be translates every time it is run