Principles of computer science

DIAGRAM: __________Main Memory ________ (Read)!_____¡(Write) Input –> Central Proecessing Unit –> Output • A structure in which computer hardware is connected and organised. • It consists of RAM and CPU interconnected by buses. • The CPU reads and writes data & program instruction to and from main memory (RAM)

Known as Random Access Memory(RAM) It stores the data & programs the CPU can access. Volatile - Loses content when power is lost. Faster and more expensive than secondary storage

A computer that is multi-purpose, can be programmed to carry out different tasks. They are able to store program instructions and data in memory.

• Control Unit (CU) • Arithmetic logic unit (ALU) • Registers • Clock

The control Unit decodes information received from main memory and coordinates the actions of the other parts of the CPU

Performs arithmetic and logic operations on data

Provides fast and temporary storage for instructions

Sends out electrical signals to synchronise the actions of the hardware components. Measured in hertz, 1 hertz = 1 “tick” per second

Busses connect the CPU with the main memory. There are 3 types of busses: • Adress bus • Data bus • Control bus

Non-volatile Allows the system to store data and programs permanently. Types: -SSD(Solid State Drives): USB drive -HDD(Hard Disc Drive): Magnetic storage -Optical Storage: DVD/CD Cheaper and slower than main memory.

Represents bits by little pools of trapped electrons on a microchip

Components inside computers have billions of transistors. Binary is used to represent the transistors inside the component. Transistors can be on or off (1 or 0).

CPU sends through the address bus the memory address of the next instruction The CU within the CPU sends a read message to the memory through control bus The content of the memory locations is sent to the CPU via the data bus General: The next instruction to be executed is transferred from the RAM to the CPU

The CU looks up the instruction in the CPUs instruction set

CU coordinates the action of other components to carry out the operation and instructs the ALU if calculations needed to be done

Components inside computers have billions of transistors. Binary is used to represent the transistors inside the component. Transistors can be on or off (1 or 0).

An unsigned integer has no positive or negative sign. Signed: -8, +8 Unsigned: 8