computer science test 1

test 1

CPU- what it does

CPU is the brain of the computer, it fetches, decodes and executes instructions stored in memory and carries out all processing tasks.

Control Unit (CU)

Manages the fetch decode execute cycle. Sends control signals to direct other parts of the system. Tells memory and ALU devices what to do.

Arithmetic Logic Unit (ALU)

performs maths operations and logic operations. Output results to the accumulator.

Registers

Very fast temporary memory inside the CPU. Used to store data, instructions and addresses during processes.

Cache memory

small, fast memory close to the CPU. Stores frequently used instructions.

clock

sends out regular pulses to control the timing of the CPU operation. Speed measured in Hertz(hz)-usually GHZ(billion cycles per second)

clock speed

Higher clock speed= CPU carries out more instructions per second. However, when more power is used, it generates more heat.

number of cores

each core can decode and execute instructions independently. More cores= more tasks handled at once. Useful for multitasking.

cache size

bigger cache=more data stored close to CPU. Reduces time waiting for data from RAM.

program counter (pc)

holds the address of the next instruction to be fetched

memory address register (mar)

holds the memiry address of data or instruction being accesssed

memory data register (mdr)

holds the actual data being transferred to or from memory

current instruction register (CIR)

holds the current instruction from being decoded and executed

accumulator

stores intermediate results of calculations carried out by the ALU

step 1 of the fetch decode execute cycle

step 1: fetch- the program counter sends the address of the next instructions to the MAR. The cpu fetches the instruction from main memory and places it in MDR. the instruction is copied from the MDR to CIR. The PC increments by 1.

step 2 of the fetch decode execute cycle

step 2:decode - the control unit interprets the instruction in the CIR. It determines what needs to be done.

step 3 of the fetch decode execute cycle

step 3: execute- The decoded instruction is carried out. E.g. ALU performs a calculation or logic operation. Then the cycle repeats millions of times per second,

secondary storage

It has slow speed. It is large and it is not volatile. It is inside the CPU and holds current data.

Cache

The speed is very fast,it is small and volatile. It is next to the CPU and stores frequently used data

RAM

it is fast and the size is medium. It is very volatile. Holds program/data in use.

Register

It is the fastest speed, it is also very small. It is not volatile. It is long term storage

clock cycle

a single tick of the cpu clock-

throughput

number of instructions processed per second

parallel processing

using multiple cores to perform several operations at once

bottleneck

when one part of the system slows down the rest

instruction set

the complete cell of the operations the CPU can perform