Computing Cpt1

AS Computing CPT1 1. Fundamentals of Computer Systems Hardware: The physical components that make up the computer. Software: The programs of sequences of instruction, which run on the computer. The processor has the following functions (fetch-execute cycle): 1. Fetches the next instruction from the main memory; 2. Decodes the fetched instruction; 3. Executes the decoded instruction.

SYSTEMS SOFTWARE – An interface between the user and the computer; Performs tasks needed to run the computer. Operating System – Interface between the user and the computer; a virtual machine. Utility Program E.g. virus scanner, disk formatter, backup program. Library Programs - Previously written program code; program files which are used by other/many applications. Compilers, assemblers, interpreters – See below.

APPLICATION SOFTWARE – a program written to perform an end user task, which is primary independent of the computer. General Purpose Application Software – Software that can be made to do many different tasks. E.g. word processor, spreadsheet, database, desktop publishing, computer-aided design and presentation packages. Special Purpose Application Software – Software to perform a specific task. E.g. payroll, account and stock control system. Bespoke Software – Software written to the specification of a particular organisation or customer. E.g. a unique database management system. Integrated Package – A single piece of software. Bit (BInary digiT) – 1 or 0 8 Bits = Byte = One Character Word Size – The numbers of bits a CPU can address/transfer/process at the same time, most computers are 32 or 64 bit.

Bus Size – The number of bits that can be transmitted together.

2. Fundamentals of Programming Assembler – Translates assembly code into machine code. Complier – Translates the whole high level language source code into object code. USE: finish development; software shipped to user. REASON: speed of execution. Interpreter – Translates one line at a time and then executes it. USE: software under development. REASON: debugging tools. Advantages of Compliers over Interpreters: • • • •

The object code can be saved on disk and run whenever required, without the need to recompile. The object code executes faster than interpreted code. The object code produced by a complier can be distributed or executed without having the complier present. The object code is more secure, as it cannot be read without a great deal of “reverse engineering”.

Advantages of Interpreters over Compliers: • • •

It is useful for program development, as there is no need for lengthy recompilation each time an error is discovered. It is easier to partially test and debug programs. Unlike a complier, if a bug or error is found the program does not have to be recompiled again as no object code is created.

A Function is always returns a value; part of an expression. A Procedure does not have to return a value; not part of an expression. Imperative – Computer executes instructions in a programmer defined sequence.

3. Fundamentals of Information and Data Representation Data – Raw facts and figures. Information - Data that has been processed and given a context. Sampling Resolution – The number of bits used to store one sound sample. Sampling Rate - The frequency at which samples are taken. Pixel (Picture Element) – The smallest resolvable rectangular area of and image.

4. Communication and Networking Serial Data Transmission – Bits are sent one after the other; along a single wire. Parallel Data Transmission – Several bits are sent at the same time; down several wires. Baud Rate – The rate at which the signal changes. Bit Rate – The number of bits per second. Bandwidth – The range of frequencies that a medium can correctly transmit. Higher the bandwidth, higher the bit rate. Asynchronous Transmission – One character at a time is sent, with each character being preceded by a start bit and followed by one or two start bits. Parity Bit – Used to check against incorrect transmission. Handshaking – The sender and receiver are both ready before transmission. Protocol – A set of rules relating to communication between devices. Local Area Network (LAN) – Connects computers in a small geographic area. Network Interface Card (NIC). Wide Area Network (WAN) – Connects geographically remote computers of networks. Internet – World-wide collections of computers using the Internet Protocol. Intranet – LAN providing Internet facilities within an organisation using the Internet Protocol. HTTP – Hypertext Transfer Protocol URL – Uniform Resource Locator Leased Line Networking – A dedicated line connecting geographically remote computer systems is permanently on. Dial-up Networking – using a telephone line to connect to a network as required. Domain Name – User friendly reference that maps to an IP address. IP Address – Numerical address use to identify an individual computer.