The contents of ROOM can't be changed and arena lost when the computer Is witched off This is known as 'non-volatile memory. Bits and bytes Computers store and process data using binary numbers. A single unit in binary is called a bit which stands for binary digit. Computer memory Is measured In bytes. One byte is made up of eight bits. 0000010 The eight-bit binary code in this byte represents the letter B. The size of a computer's memory is normally measured in kilobytes (KGB), megabytes (MBA) or gigabytes (B).

The table below shows some of the main units of size that we use to measure computer memory. Unit kilobyte megabyte gigabyte terabyte Abbreviation KGB MBA KGB TAB Size 1 1024 bytes 1 1024 KGB 1 B = 1024 MBA 1 TAB ICES CIT Cambridge university Press 2010 Revision notes: Module 1 1 Mall components = 1024 KGB Hardware - all the parts of the physical equipment which makes the computer. Software - all the programs that allow the hardware to carry out the data processing.

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Input Central processing unit (CPU) Backing store Output FIFO Computers can work 24 hours per day, 365 days per year. ; Computers make some jobs possible. Disadvantages of using computers ; Computers can replace people's jobs. ; Computers hold personal information which could be misused. Computers can fail and without them the Job may not get done. Processing data Computers can: ; calculate ; sort ; search ; store ; draw. GEESE CIT O Cambridge university press 2010 Revision notes: Module 1 2 Operating systems An operating system (SO) is a set of programs that controls how the hardware and applications of a computer works. An SO is the way of communicating between the user and the computer. The SO loads and runs the other software application programs and other Jobs. The operating system on a computer means that usually only certain applications will run on that computer.

Functions The operating system: ; enables communication between the user and the computer; ; loads and runs applications programs as well as other Jobs; ; will only run applications written for that particular type of SO; ; handles input and output: - taking data from the input devices and sending it to RAM; - taking output and sending it to the correct output device; ; handles the transfer of data from memory to and from the backing storage devices; ; allocates memory space to programs and data; ; loads and runs the applications software in memory; ; handles any errors while the software is running; ; manages system security, with user ID and passwords; ; provides a human-computer interface, or HCI, for the user.

Human- computer interface (HCI) This is the method by which the users communicates with the computer, sometimes called the user interface. Two type of HCI are: ; command- line interface ; graphical user interface or GIG-Jell. Command-line interface The user types in the instructions using command words. The main advantage of command-driven interfaces is that, providing the user knows the commands, they can be quick to carry out, since they require less translation by he SO than Guise. They can also be used in batch files to carry out repetitive administration tasks that would take a long time using a GIG-Jell. Graphical user interface The most widely used type of graphical user interfaces are WIMP (Windows Icons Menu Pointer) systems.

The main advantage of a GUI it is easy to use. The main disadvantage is the large amount of memory, RAM and disk space that is needed. Software There are two main types of computer software - system software and application software. Application software is used in particular situations and can be general- repose (the same software used in differing situations) or specialist/custom-made (can only be used in one particular situation). General purpose A general-purpose application package (generic) is software that can perform different related tasks. Word processors, spreadsheets, databases, graphics and presentation software are all examples of application packages.