Summary OCR COMPUTER SCIENCE GCSE NOTES PT 1 (I will make more)
17 views 1 purchase
Course
Computing
Institution
GCSE
This document consists of a a section of a summary of GCSE Computer Science. This is not all of paper 1 content, and I am happy to make more parts so the full CS Paper 1 notes are done. I am currently a CS A-level student who managed to get a 8 in GCSE. I recommend students to use this especially a...
- A computer is a device that stores data in the form of binary (zeros and ones) because it is
built from transistors, which are basically switches with two conditions (ON or OFF). A
computer has both hardware (cpu, ram, motherboard, graphics card) and software
(applications) with the purpose of doing general tasks.
What is an input device?
- A peripheral that transfers data into another device to be processed
- Examples of an input device: joystick, mouse, keyboard, microphone
What is an output device?
- A peripheral that transfers data out of a device to the user to understand
- Examples of an output device: monitor, speakers, printers
Hardware:
- What is it: physical and electrical components inside a computer system
- Examples: CPU, RAM, PSU, HDD/SSD
Software;
- All the programs and applications that runs on a computer. There are two types of software;
application software and system software.
The CPU – central processing unit:
What is it: It is a piece of hardware inside a computer that does the fetch-decode-execute cycle.
Parts of the CPU:
- MAR (memory address register) – holds the address of the instruction that is being fetched
- MDR (memory data register) – holds the data that will be fetched
- PC (program counter) – holds the next memory address
, - ALU (Arithmetic Logic Unit) –carries out any arithmetic (+,-,*,/), logical (and, or, not) or shift
operations
- Accumulator – holds the value from the ALU
- CU (control unit) – decodes, and executes instructions and controls the flow of data
- Cache: tiny but super-fast memory that’s purpose is to hold frequently used instructions
The fetch-decode-execute cycle (detailed):
- The memory address is copied into the MAR from the Program counter
- Instructions are fetched from main memory
- Those instructions are then copied to the MDR
- They are then decoded by the CU and finally executed
(The cycle repeats)
Simple descriptions of the fde cycle:
- Data is fetched from main memory
- Data is then decoded and execution occurs.
Features of the CPU that affects performance:
- Clockspeed – describes the number of fetch-decode-execute cycles occurring per second but
is noted in Hertz
- Cache size – bigger cache size will mean more memory will be stored there rather than RAM,
which has a significantly slower access time
- Number of cores – more cores enables parallel processing which is when multiple CPUs are
working simultaneously and this greatly speeds up a computer performance.
Virtual memory:
Virtual memory is often needed in a computer when there is insufficient space in RAM. VM causes
data that hasn’t been used recently to be moved to a hard drive or a solid-state drive. Virtual
memory does boost a computer’s performance. However, the disadvantages of using VM, is that it is
very slow in comparison to RAM, Cache, a CPU’s registers etc.
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller jinalle. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $9.89. You're not tied to anything after your purchase.
