Topic 2—Computer organization

2.1.11 Define the Boolean operators: AND, OR, NOT, NAND, NOR and XOR.

AND: true only if both of the inputs are true. OR: true if at least one of the inputs are true. NOT: inverts a value, makes a false from a true and vice versa. NAND: NOT + AND gates together. False if both the inputs are true, otherwise true. NOR: NOT + OR gates together. Only true of both of the inputs are false, otherwise true. XOR: exclusive OR. Only true if only one of the inputs is true, otherwise false.

2.1.4 Explain the machine instruction cycle.

Fetch - get an instruction from cache or memory. Decode - translate it into computer commands (machine language). Execute - actually process the command. Store - write the result to memory.

2.1.9 Define the terms: bit, byte, binary, denary/decimal, hexadecimal.

Bit: smallest unit in computers, either a 1 or a 0. Byte: a group of 8 bits. Binary: computers use the binary (base 2) number system. Decimal: This is the number system we use (base 10). Hexadecimal: Base 16 number system. It has a base that is a power of 2, so we can use it to make reading binary codes shorter and thus easier to read. 4 binary characters grouped together give a hexadecimal character.

2.1.1 Outline the architecture of the central processing unit (CPU) and the functions of the arithmetic logic unit (ALU) and the control unit (CU) and the registers within the CPU.

Central Processing Unit (CPU) - the key component of a computer system that contains the circuitry necessary to interpret and execute program instructions. Arithmetic Logic Unit (ALU) - it is a circuit that is part of the CPU that does all the arithmetic calculations. Control Unit (CU) - it is the control circuit of the CPU that handles the loading of new commands into the CPU and the decoding of these commands. It also directs the data flow and the operation of the ALU. Registers are small, very fast circuits that store intermediate values from calculations or instructions inside the CPU. They are often referred to as cache memory inside the CPU. There are two types of these memory we need to know: The Memory Address Register (MAR) and the Memory Data Register (MDR). The MAR holds the address of the next memory cell that data will need to be read from or written to, while the MDR holds data that will be written to the RAM or that was read from RAM. The MAR gives the address the data of the MDR will be read from or written to.

2.1.10 Outline the way in which data is represented in the computer

Computer work with the binary number system, so everything in them is represented in 1s and 0s. So, the data that we want to store in the computer needs to be encoded in 1s and 0s. For different media types, different encodings exist. Text needs to be also transformed into 0s and 1s. To do this, a character set is used. A character set is a collection of characters and the binary codes that represent them. Today, the most used character sets are ASCII and UTF. ASCII: stands for American Standard Code for Information Interchange. It uses 7 (later 8) bits to encode the characters, so in total 28=256 different characters can be represented. UTF: is a superset of ASCII. It was developed because people realized that the 256 characters of ASCII are not enough to satisfy our need for a suitable number of characters. The goal of the maker of UTF is nothing less than to represent every character humans have ever used. Strings: representation of characters in a continuous bit chain Integers: representation of numbers in computers. Whole numbers. Negatives can be represented by the 'two's complement' method. Floats: representation of fractions within the computer. It is a special version of the scientific notation. It consists of a sign bit, the mantissa, the number itself, and the exponent which states how many characters left or right of the number the radix point 'floats'. The radix point is the version of the decimal point that can be applied in any number system. In the 64 bit float, 1 bit is used for the sign, 52 are used for the mantissa and 11 are used for the exponent.

2.1.6 Describe the main functions of an operating system.

Coordinates all the computers resources including keyboard, mouse, printer, monitor, storage devices and memory. Users interact with the application programs and computer hardware through a user interface. Loads and runs applications such as word processors and games. Uses utility programs for maintenance and repairs. All programs that need hardware resources must go through the operating system.

2.1.3 Explain the use of cache memory

It is a type of small, high-speed memory inside the CPU used to hold frequently used data, so that the CPU needs to access the much slower RAM less frequently.

2.1.8 Identify common features of applications.

Menus, buttons, toolbars, ribbons, icons, and slides.

2.1.5 Identify the need for persistent storage.

Persistent storage is needed to store data and programs after the computer is turned off in order to avoid the need to reinstall all the data and programs every time the computer is restarted. Also, RAM is limited in a computer while large amounts of secondary storage are relatively cheap, so storing unused data and programs in secondary storage is useful to make space for running ones.

2.1.2 Describe primary memory.

Primary memory is computer memory that is accessed directly by the CPU. Random Access Memory (RAM) it is memory unit that can be read and written from at any location. It is used as primary memory in computers to hold data and instructions. It is volatile, so it loses its contents when power is turned off. Read-Only Memory (ROM) is memory unit that can only be read from. It is non-volatile, so it keeps its contents when power is turned off. It is used to store the BIOS (today UEFI) of the computer, the small control program that directs turning on the computer.

2.1.7 Outline the use of a range of application software.

Word processor: A program to create and edit continuous texts. Spreadsheet: A program to manage calculations on complex amounts of data. Desktop Publishing: A program to edit media in a way to be published, like magazines, books or posters. Computer Aided Design (CAD): Software to digitally design and edit parts to be manufactured. Often includes a Computer Aided Manufacturing (CAM) module to be able to use the model to directly produce a prototype.