Computer Science Basics

Computer Science Overview

• Binary addition follows specific rules, including carrying digits and rounding down in case of overflow errors.

• Character sets, such as ASCII and Unicode, allocate binary numbers to represent characters, with Unicode having more room for different languages.

• Images are represented by pixels, and the resolution is the number of pixels, while color depth refers to the number of bits per pixel.

• Metadata is stored with images, providing essential details about the image.

• Sound is converted from analog to digital through sampling and has a sample rate and bit depth.

• Compression reduces file size, with lossy compression deleting parts of the file and lossless compression rearranging the file.

• LANs are local area networks, while WANs are wide area networks that cover larger areas and have infrastructure owned by multiple entities.

• In client-server networks, devices either act as clients or servers, with servers controlling what is given and who receives it. In peer-to-peer networks, devices can act as both clients and servers.

• Network topologies include star and mesh, with star relying on a central device and mesh having direct connections to every other device.

• Different hardware, such as wireless access points and routers, play specific roles in networks.

• Bandwidth refers to the maximum amount of data that can be transferred at a given time, and it is shared among devices on a network.

• IP addresses provide geographical information about devices, and the domain name system translates URLs into IP addresses. The cloud hosts resources and files accessed through the internet.

• Protocols are sets of rules enabling device communication, and they are organized into layers. Key protocols include TCP, POP, IMAP, SMTP, and Ethernet.Operating Systems and Multitasking

• Operating systems determine when to move data across different components

• They also decide when to delete data from RAM

• Operating systems manage the execution of programs

• Multitasking is a feature supported by most operating systems

• Multitasking allows for rapid switching between executing programs

• This gives the illusion of multiple tasks happening simultaneously

• In reality, the tasks are being rapidly switched between

• Multitasking is managed by the operating system

• Peripherals are external devices connected to the system

• The text does not provide specific information about peripherals

• Peripherals can include devices like keyboards, mice, printers, etc.

• The role of peripherals in the context of the text is unclear

Overview of OCR GCSE Computer Science Paper One

• The CPU (central processing unit) is responsible for carrying out program instructions using data.
• The CPU consists of components such as the ALU (arithmetic logic unit), control unit, cache, and registers.
• Cache is a small, fast type of memory that holds frequently accessed items.
• Registers are ultra small and ultra fast and store data and instructions within the CPU.
• The Von Neumann architecture is the structure of a CPU and consists of components such as the ALU, control unit, and registers.
• The CPU carries out a fetch execute cycle, which involves fetching instructions from memory, decoding them, and executing them.
• The clock speed of the CPU determines how often the fetch execute cycle is repeated per second.
• Multiple cores in a CPU allow for parallel execution of instructions, increasing performance.
• Cache size affects performance by reducing reliance on slower RAM.
• Embedded systems are computers integrated into other devices, such as household appliances and cars.
• Primary storage consists of RAM and ROM, while secondary storage is where programs and data are stored long-term.
• Secondary storage options include magnetic storage (hard disk drives), optical storage (DVDs), and solid-state storage (SSDs).
• Binary units, such as bits, nibbles, and bytes, are used to represent and store data. Conversion between binary, hexadecimal, and decimal can be done using place value tables.