Instructions Slides 3,4,5 are general questions that you should be able to answer. Use slides 6-27 to answer the questions. Write your answers in a separate word document. Slides 28 – 40 are sample test questions. The real test will have similar questions. Test will be next Friday (13/03)

Content: Hardware CPU memory Storage devices What’s responsible for the speed of the computer Peripherals

Computer systems define a computer system describe the importance of computer systems in the modern world explain the need for reliability in computer systems explain the need for adherence to suitable professional standards in the development, use and maintenance of computer systems explain the importance of ethical, environmental and legal considerations when creating computer systems. The central processing unit (CPU) state the purpose of the CPU describe the function of the CPU as fetching and executing instructions stored in memory explain how common characteristics of CPUs such as clock speed, cache size and number of cores affect their performance.

Memory describe the difference between RAM and ROM explain the need for ROM in a computer system describe the purpose of RAM in a computer system explain how the amount of RAM in a personal computer affects the performance of the computer explain the need for virtual memory describe cache memory describe flash memory discuss how changes in memory technologies are leading to innovative computer designs. Secondary storage explain the need for secondary storage describe common storage technologies such as optical, magnetic and solid state select suitable storage devices and storage media for a given application and justify their choice using characteristics such as capacity, speed, portability, durability and reliability.

Input and output devices understand the need for input and output devices describe suitable input devices for a wide range of computer controlled situations describe suitable output devices for a wide range of computer controlled situations discuss input and output devices for users with specific needs.

CPU: The part of the computer that carries out the instructions in the software Executes programs and manages hardware

The CPU is made up of the ALU control unit and cache. Program instructions and data move between the RAM and processor using internal connections using system buses. System bus: transfer data between the CPU and other pieces of hardware

ALU Also known as the arithmetic logic unit. It’s the part of the computer/CPU which does all of the arithmetic and logic operations.

Control unit Also known as the CU It’s the part of the computer which needs the CPU to control the data in the system

cache memory It’s known as high speed memory which is used by the computer. The computer uses cache memory to store data while its being processed.

Secondary storage: when you store data permanently Secondary storage: when you store data permanently. System bus: transfers data between the CPU and other pieces of hardware. Bottle neck: a piece of the computer which is slow and it slows everything else down as well in the computer.

To run the program the processor fetches an instruction, decodes it and the executes it. This is called the fetch-decode-execute cycle. The speed of the processor is quoted as the clock speed, in Hertz. Hertz is the number of electrical cycles per second. The speed of the processor is measured in MHz (megahertz) or GHz (gigahertz)

RAM: Main memory of a computer that stores data, applications and the operating system whilst in use. When the power is turned off, RAM loses its data. This means that RAM is volatile.

The more RAM a computer has, it can deal with larger programs, larger data files and can run more programs and data files at the same time. It can also mean that the computer can multi-task more. This means the computer is dealing with several programs and files at the same time.

ROM The ROM contains the program that is used to start up the computer.   This is also called the boot program because the process of starting up the computer is also called ‘booting up’ the computer. ROM is not volatile and is the same even when the computer is turned off.

The program inside the ROM is not easily deleted or changed.   This means the boot program will always be there when the computer is started. This is why any computer system needs some ROM.

On a standard personal computer, the boot program does the following things:   It performs some basic checks. It finds the operating system and loads it into the RAM. It then hands control over to the operating system.

Virtual memory   Virtual memory is a part of the hard drive (which is secondary storage) Virtual memory is part of the hard drive used as an extension to the RAM. It is used when the computer does not have enough RAM to hold all the data and programs that a user wants.

Flash memory   Used in cameras, USB drives and in other secondary storage devices such as in portable devices and in large installations as removable memory. It provides low cost portable and removable storage for a range of devices such as cameras, phones and USB drives for transferring and storing personal files. Flash memory is not as fast as RAM; although it is a form of RAM

Storage devices Any device that is used to store data is known as a storage device. Input device An input device is a piece of hardware that is used to enter data into a computer. E.g. mouse Output device An output device is a piece of hardware that is used to display or output data which has been processed or has been stored on a computer. E.g. speakers

How the data is stored depends on these factors: Capacity: the amount of data to be stored/ size of the file Speed: how quickly the user needs to be able to access the data from the storage device Portability: whether the data needs to be moved from one place to another such as from home to school. Durability: how long the storage media can reasonably be expected to last Reliability: whether the data can always be accessed reliably and in the format in which it was saved

Most computers have some form of internal storage. Internal storage devices Internal storage devices basically means that it’s found inside the computer case. Most computers have some form of internal storage. The most common type of internal storage is the hard disk. Internal storage is needed to hold the operating system so that the computer is able to access the input and output devices. It’s also used to store the applications software that you use and the original copies of your data files. Internal storage allows the data and apps to be loaded very rapidly into memory, ready for use.

The data can accessed much faster that data which is stored on an external storage device. This is because internal storage devices are connected directly to the motherboard and its data bus whereas external devices are connected through a hardware interface such as a USB, which means that they are considerably slower to access. Internal storage also means that if the computer is moved around, it will still retain its most commonly used data.

External Storage Devices External drives are connected to the computer with a cable plugged into a suitable interface such as an USB port. Data then passes back and forth across the interface. The main advantage of external drives is that they are portable and so data is easily moved from one location to another. External drives also allow safe backup of internally stored data. The main disadvantage compared to an internal drive is data transfer is slower and they also take up space around the computer. Constant plugging in and out can also physically wear out the port over time.  

External storage takes many forms, for example: portable hard disks magnetic tape memory stick / flash drive solid state memory cards DVD or CDs

Properties of a hard disk Property Notes Type of storage Magnetic Data access Direct access Cost of storage Hard disks hold a vast amount of data and are relatively cheap; so on a per-byte basis they are amongst the cheapest form of storage; although magnetic tape is cheaper. Capacity Can be a terabyte or more Speed An internal hard disk is faster than external storage devices. Portability An internal hard disk is not intended to be portable. An external hard disk used for backing up data is portable. Durability Very durable- it can last for years if treated carefully. Reliability As long as its not damaged, a hard disk is very reliable.

Peripherals: A peripheral is any hardware device which connects to the computer and is controlled by the Central Processing Unit (CPU) - with the exception of memory. When you are trying to think of examples of peripherals, think of things which plug into the back of the computer casing, for example: monitor keyboard mouse printer scanner speakers external hard drive